Add found messages and fix minor rendering issue with groups containing arrows to sides [#37]

lib/sequence-diagram.js

@@ -645,8 +645,13 @@ define('sequence/CodeMirrorMode',['core/ArrayUtilities'], (array) => {
 			)};
 		}
 
+		const colonTextToEnd = {
+			type: 'operator',
+			suggest: true,
+			then: {'': textToEnd, '\n': hiddenEnd},
+		};
 		const agentListToText = agentListTo({
-			':': {type: 'operator', suggest: true, then: {'': textToEnd}},
+			':': colonTextToEnd,
 		});
 		const agentList2ToText = {type: 'variable', suggest: 'Agent', then: {
 			'': 0,
@@ -656,7 +661,7 @@ define('sequence/CodeMirrorMode',['core/ArrayUtilities'], (array) => {
 		const singleAgentToText = {type: 'variable', suggest: 'Agent', then: {
 			'': 0,
 			',': CM_ERROR,
-			':': {type: 'operator', suggest: true, then: {'': textToEnd}},
+			':': colonTextToEnd,
 		}};
 		const agentToOptText = {type: 'variable', suggest: 'Agent', then: {
 			'': 0,
@@ -700,7 +705,7 @@ define('sequence/CodeMirrorMode',['core/ArrayUtilities'], (array) => {
 			};
 		}
 
-		function makeOpBlock(exit) {
+		function makeOpBlock(exit, sourceExit) {
 			const op = {type: 'operator', suggest: true, then: {
 				'+': CM_ERROR,
 				'-': CM_ERROR,
@@ -729,13 +734,13 @@ define('sequence/CodeMirrorMode',['core/ArrayUtilities'], (array) => {
 					}},
 					'': exit,
 				}},
-				'*': {type: 'operator', suggest: true, then: {
+				'*': {type: 'operator', suggest: true, then: Object.assign({
 					'+': op,
 					'-': op,
 					'*': CM_ERROR,
 					'!': CM_ERROR,
 					'': exit,
-				}},
+				}, sourceExit)},
 				'!': op,
 				'': exit,
 			};
@@ -745,7 +750,10 @@ define('sequence/CodeMirrorMode',['core/ArrayUtilities'], (array) => {
 			const connect = {
 				type: 'keyword',
 				suggest: true,
-				then: makeOpBlock(agentToOptText),
+				then: makeOpBlock(agentToOptText, {
+					':': colonTextToEnd,
+					'\n': hiddenEnd,
+				}),
 			};
 
 			const then = {'': 0};
@@ -756,7 +764,10 @@ define('sequence/CodeMirrorMode',['core/ArrayUtilities'], (array) => {
 				override: 'Label',
 				then: {},
 			};
-			return makeOpBlock({type: 'variable', suggest: 'Agent', then});
+			return makeOpBlock(
+				{type: 'variable', suggest: 'Agent', then},
+				then
+			);
 		}
 
 		const BASE_THEN = {
@@ -1597,10 +1608,10 @@ define('sequence/Parser',[
 	})());
 
 	const CONNECT_AGENT_FLAGS = {
-		'*': 'begin',
+		'*': {flag: 'begin', allowBlankName: true, blankNameFlag: 'source'},
-		'+': 'start',
+		'+': {flag: 'start'},
-		'-': 'stop',
+		'-': {flag: 'stop'},
-		'!': 'end',
+		'!': {flag: 'end'},
 	};
 
 	const TERMINATOR_TYPES = [
@@ -1712,7 +1723,7 @@ define('sequence/Parser',[
 		return -1;
 	}
 
-	function readAgentAlias(line, start, end, enableAlias) {
+	function readAgentAlias(line, start, end, {enableAlias, allowBlankName}) {
 		let aliasSep = -1;
 		if(enableAlias) {
 			aliasSep = findToken(line, 'as', start);
@@ -1720,7 +1731,7 @@ define('sequence/Parser',[
 		if(aliasSep === -1 || aliasSep >= end) {
 			aliasSep = end;
 		}
-		if(start >= aliasSep) {
+		if(start >= aliasSep && !allowBlankName) {
 			throw makeError('Missing agent name', errToken(line, start));
 		}
 		return {
@@ -1734,25 +1745,31 @@ define('sequence/Parser',[
 		aliases = false,
 	} = {}) {
 		const flags = [];
+		const blankNameFlags = [];
 		let p = start;
+		let allowBlankName = false;
 		for(; p < end; ++ p) {
 			const token = line[p];
 			const rawFlag = tokenKeyword(token);
 			const flag = flagTypes[rawFlag];
-			if(flag) {
+			if(!flag) {
-				if(flags.includes(flag)) {
-					throw makeError('Duplicate agent flag: ' + rawFlag, token);
-				}
-				flags.push(flag);
-			} else {
 				break;
 			}
+			if(flags.includes(flag.flag)) {
+				throw makeError('Duplicate agent flag: ' + rawFlag, token);
 			}
-		const {name, alias} = readAgentAlias(line, p, end, aliases);
+			allowBlankName = allowBlankName || Boolean(flag.allowBlankName);
+			flags.push(flag.flag);
+			blankNameFlags.push(flag.blankNameFlag);
+		}
+		const {name, alias} = readAgentAlias(line, p, end, {
+			enableAlias: aliases,
+			allowBlankName,
+		});
 		return {
 			name,
 			alias,
-			flags,
+			flags: name ? flags : blankNameFlags,
 		};
 	}
 
@@ -2091,8 +2108,8 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 		equals: (a, b) => {
 			return a.id === b.id;
 		},
-		make: (id, {anchorRight = false} = {}) => {
+		make: (id, {anchorRight = false, isVirtualSource = false} = {}) => {
-			return {id, anchorRight};
+			return {id, anchorRight, isVirtualSource};
 		},
 		indexOf: (list, gAgent) => {
 			return array.indexOf(list, gAgent, GAgent.equals);
@@ -2100,6 +2117,14 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 		hasIntersection: (a, b) => {
 			return array.hasIntersection(a, b, GAgent.equals);
 		},
+		addNearby: (target, reference, item, offset) => {
+			const p = array.indexOf(target, reference, GAgent.equals);
+			if(p === -1) {
+				target.push(item);
+			} else {
+				target.splice(p + offset, 0, item);
+			}
+		},
 	};
 
 	const NOTE_DEFAULT_G_AGENTS = {
@@ -2108,6 +2133,8 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 		'note right': [GAgent.make(']')],
 	};
 
+	const SPECIAL_AGENT_IDS = ['[', ']'];
+
 	const MERGABLE = {
 		'agent begin': {
 			check: ['mode'],
@@ -2282,7 +2309,7 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 			this.activeGroups = new Map();
 			this.gAgents = [];
 			this.labelPattern = null;
-			this.blockCount = 0;
+			this.nextID = 0;
 			this.nesting = [];
 			this.markers = new Set();
 			this.currentSection = null;
@@ -2311,7 +2338,7 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 			this.endGroup = this.endGroup.bind(this);
 		}
 
-		toGAgent({alias, name}) {
+		toGAgent({name, alias, flags}) {
 			if(alias) {
 				if(this.agentAliases.has(name)) {
 					throw new Error(
@@ -2330,7 +2357,9 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 				}
 				this.agentAliases.set(alias, name);
 			}
-			return GAgent.make(this.agentAliases.get(name) || name);
+			return GAgent.make(this.agentAliases.get(name) || name, {
+				isVirtualSource: flags.includes('source'),
+			});
 		}
 
 		addStage(stage, isVisible = true) {
@@ -2366,7 +2395,12 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 		}
 
 		defineGAgents(gAgents) {
-			array.mergeSets(this.currentNest.gAgents, gAgents, GAgent.equals);
+			array.mergeSets(
+				this.currentNest.gAgents,
+				gAgents.filter((gAgent) =>
+					!SPECIAL_AGENT_IDS.includes(gAgent.id)),
+				GAgent.equals
+			);
 			array.mergeSets(this.gAgents, gAgents, GAgent.equals);
 		}
 
@@ -2390,7 +2424,9 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 		validateGAgents(gAgents, {
 			allowGrouped = false,
 			rejectGrouped = false,
+			allowVirtual = false,
 		} = {}) {
+			/* jshint -W074 */ // agent validity checking requires several steps
 			gAgents.forEach((gAgent) => {
 				const state = this.getGAgentState(gAgent);
 				if(state.covered) {
@@ -2404,6 +2440,9 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 				if(state.blocked && (!allowGrouped || state.group === null)) {
 					throw new Error('Duplicate agent name: ' + gAgent.id);
 				}
+				if(!allowVirtual && gAgent.isVirtualSource) {
+					throw new Error('cannot use message source here');
+				}
 				if(gAgent.id.startsWith('__')) {
 					throw new Error(gAgent.id + ' is a reserved name');
 				}
@@ -2497,12 +2536,18 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 			this.replaceGAgentState(rightGAgent, AgentState.LOCKED);
 			this.nesting.push(this.currentNest);
 
-			return {gAgents, stages};
+			return {stages};
 		}
 
 		nextBlockName() {
-			const name = '__BLOCK' + this.blockCount;
+			const name = '__BLOCK' + this.nextID;
-			++ this.blockCount;
+			++ this.nextID;
+			return name;
+		}
+
+		nextVirtualAgentName() {
+			const name = '__' + this.nextID;
+			++ this.nextID;
 			return name;
 		}
 
@@ -2706,9 +2751,13 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 			let ind1 = GAgent.indexOf(this.gAgents, gAgents1[0]);
 			let ind2 = GAgent.indexOf(this.gAgents, gAgents2[0]);
 			if(ind1 === -1) {
-				ind1 = this.gAgents.length;
+				// Virtual sources written as '* -> Ref' will spawn to the left,
+				// not the right (as non-virtual agents would)
+				ind1 = gAgents1[0].isVirtualSource ? -1 : this.gAgents.length;
 			}
 			if(ind2 === -1) {
+				// Virtual and non-virtual agents written as 'Ref -> *' will
+				// spawn to the right
 				ind2 = this.gAgents.length;
 			}
 			if(ind1 === ind2) {
@@ -2755,21 +2804,79 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 			return {beginGAgents, endGAgents, startGAgents, stopGAgents};
 		}
 
+		makeVirtualAgent(anchorRight) {
+			const virtualGAgent = GAgent.make(this.nextVirtualAgentName(), {
+				anchorRight,
+				isVirtualSource: true,
+			});
+			this.replaceGAgentState(virtualGAgent, AgentState.LOCKED);
+			return virtualGAgent;
+		}
+
+		addNearbyAgent(gAgentReference, gAgent, offset) {
+			GAgent.addNearby(
+				this.currentNest.gAgents,
+				gAgentReference,
+				gAgent,
+				offset
+			);
+			GAgent.addNearby(
+				this.gAgents,
+				gAgentReference,
+				gAgent,
+				offset
+			);
+		}
+
+		expandVirtualSourceAgents(gAgents) {
+			if(gAgents[0].isVirtualSource) {
+				if(gAgents[1].isVirtualSource) {
+					throw new Error('Cannot connect found messages');
+				}
+				if(SPECIAL_AGENT_IDS.includes(gAgents[1].id)) {
+					throw new Error(
+						'Cannot connect found messages to special agents'
+					);
+				}
+				const virtualGAgent = this.makeVirtualAgent(true);
+				this.addNearbyAgent(gAgents[1], virtualGAgent, 0);
+				return [virtualGAgent, gAgents[1]];
+			}
+			if(gAgents[1].isVirtualSource) {
+				if(SPECIAL_AGENT_IDS.includes(gAgents[0].id)) {
+					throw new Error(
+						'Cannot connect found messages to special agents'
+					);
+				}
+				const virtualGAgent = this.makeVirtualAgent(false);
+				this.addNearbyAgent(gAgents[0], virtualGAgent, 1);
+				return [gAgents[0], virtualGAgent];
+			}
+			return gAgents;
+		}
+
 		handleConnect({agents, label, options}) {
 			const flags = this.filterConnectFlags(agents);
 
 			let gAgents = agents.map(this.toGAgent);
-			this.validateGAgents(gAgents, {allowGrouped: true});
+			this.validateGAgents(gAgents, {
+				allowGrouped: true,
+				allowVirtual: true,
+			});
 
 			const allGAgents = array.flatMap(gAgents, this.expandGroupedGAgent);
-			this.defineGAgents(allGAgents);
+			this.defineGAgents(allGAgents
+				.filter((gAgent) => !gAgent.isVirtualSource)
+			);
 
 			gAgents = this.expandGroupedGAgentConnection(gAgents);
+			gAgents = this.expandVirtualSourceAgents(gAgents);
 			const agentIDs = gAgents.map((gAgent) => gAgent.id);
 
 			const implicitBeginGAgents = (agents
 				.filter(PAgent.hasFlag('begin', false))
 				.map(this.toGAgent)
+				.filter((gAgent) => !gAgent.isVirtualSource)
 			);
 			this.addStage(this.setGAgentVis(implicitBeginGAgents, true, 'box'));
 
@@ -2866,7 +2973,7 @@ define('sequence/Generator',['core/ArrayUtilities'], (array) => {
 			this.agentAliases.clear();
 			this.activeGroups.clear();
 			this.gAgents.length = 0;
-			this.blockCount = 0;
+			this.nextID = 0;
 			this.nesting.length = 0;
 			this.labelPattern = [{token: 'label'}];
 		}
@@ -3457,6 +3564,7 @@ define('sequence/components/BaseComponent',[],() => {
 			theme,
 			agentInfos,
 			visibleAgentIDs,
+			momentaryAgentIDs,
 			textSizer,
 			addSpacing,
 			addSeparation,
@@ -3469,6 +3577,7 @@ define('sequence/components/BaseComponent',[],() => {
 			theme,
 			agentInfos,
 			visibleAgentIDs,
+			momentaryAgentIDs,
 			textSizer,
 			addSpacing,
 			addSeparation,
@@ -4211,10 +4320,12 @@ define('sequence/components/AgentHighlight',['./BaseComponent'], (BaseComponent)
 });
 
 define('sequence/components/Connect',[
+	'core/ArrayUtilities',
 	'./BaseComponent',
 	'svg/SVGUtilities',
 	'svg/SVGShapes',
 ], (
+	array,
 	BaseComponent,
 	svg,
 	SVGShapes
@@ -4318,6 +4429,18 @@ define('sequence/components/Connect',[
 	];
 
 	class Connect extends BaseComponent {
+		separationPre({agentIDs}, env) {
+			const r = env.theme.connect.source.radius;
+			agentIDs.forEach((id) => {
+				const agentInfo = env.agentInfos.get(id);
+				if(!agentInfo.isVirtualSource) {
+					return;
+				}
+				agentInfo.currentRad = r;
+				agentInfo.currentMaxRad = Math.max(agentInfo.currentMaxRad, r);
+			});
+		}
+
 		separation({label, agentIDs, options}, env) {
 			const config = env.theme.connect;
 
@@ -4359,6 +4482,8 @@ define('sequence/components/Connect',[
 					) * 2
 				);
 			}
+
+			array.mergeSets(env.momentaryAgentIDs, agentIDs);
 		}
 
 		renderSelfConnect({label, agentIDs, options}, env) {
@@ -4436,14 +4561,59 @@ define('sequence/components/Connect',[
 			);
 		}
 
+		renderSimpleLine(x0, x1, options, env) {
+			const dir = (x0 < x1) ? 1 : -1;
+
+			const config = env.theme.connect;
+			const line = config.line[options.line];
+			const lArrow = ARROWHEADS[options.left];
+			const rArrow = ARROWHEADS[options.right];
+
+			const rendered = line.renderFlat(line.attrs, {
+				x1: x0,
+				dx1: lArrow.lineGap(env.theme, line.attrs) * dir,
+				x2: x1,
+				dx2: -rArrow.lineGap(env.theme, line.attrs) * dir,
+				y: env.primaryY,
+			});
+			env.shapeLayer.appendChild(rendered.shape);
+			return rendered;
+		}
+
+		renderSimpleArrowheads(options, renderedLine, env, dir) {
+			const lArrow = ARROWHEADS[options.left];
+			const rArrow = ARROWHEADS[options.right];
+
+			lArrow.render(env.shapeLayer, env.theme, renderedLine.p1, dir);
+			rArrow.render(env.shapeLayer, env.theme, renderedLine.p2, -dir);
+
+			return {lArrow, rArrow};
+		}
+
+		renderVirtualSources(from, to, renderedLine, env) {
+			const config = env.theme.connect.source;
+
+			if(from.isVirtualSource) {
+				env.shapeLayer.appendChild(config.render({
+					x: renderedLine.p1.x - config.radius,
+					y: renderedLine.p1.y,
+					radius: config.radius,
+				}));
+			}
+			if(to.isVirtualSource) {
+				env.shapeLayer.appendChild(config.render({
+					x: renderedLine.p2.x + config.radius,
+					y: renderedLine.p2.y,
+					radius: config.radius,
+				}));
+			}
+		}
+
 		renderSimpleConnect({label, agentIDs, options}, env) {
 			const config = env.theme.connect;
 			const from = env.agentInfos.get(agentIDs[0]);
 			const to = env.agentInfos.get(agentIDs[1]);
 
-			const lArrow = ARROWHEADS[options.left];
-			const rArrow = ARROWHEADS[options.right];
-
 			const dir = (from.x < to.x) ? 1 : -1;
 
 			const height = (
@@ -4469,18 +4639,12 @@ define('sequence/components/Connect',[
 				SVGTextBlockClass: env.SVGTextBlockClass,
 			});
 
-			const line = config.line[options.line];
+			const rendered = this.renderSimpleLine(x0, x1, options, env);
-			const rendered = line.renderFlat(line.attrs, {
+			const {
-				x1: x0,
+				lArrow,
-				dx1: lArrow.lineGap(env.theme, line.attrs) * dir,
+				rArrow
-				x2: x1,
+			} = this.renderSimpleArrowheads(options, rendered, env, dir);
-				dx2: -rArrow.lineGap(env.theme, line.attrs) * dir,
+			this.renderVirtualSources(from, to, rendered, env);
-				y,
-			});
-			env.shapeLayer.appendChild(rendered.shape);
-
-			lArrow.render(env.shapeLayer, env.theme, rendered.p1, dir);
-			rArrow.render(env.shapeLayer, env.theme, rendered.p2, -dir);
 
 			const arrowSpread = Math.max(
 				lArrow.height(env.theme),
@@ -4996,6 +5160,7 @@ define('sequence/Renderer',[
 				theme: this.theme,
 				agentInfos: this.agentInfos,
 				visibleAgentIDs: this.visibleAgentIDs,
+				momentaryAgentIDs: agentIDs,
 				textSizer: this.sizer,
 				addSpacing,
 				addSeparation: this.addSeparation,
@@ -5200,6 +5365,7 @@ define('sequence/Renderer',[
 					id: agent.id,
 					formattedLabel: agent.formattedLabel,
 					anchorRight: agent.anchorRight,
+					isVirtualSource: agent.isVirtualSource,
 					index,
 					x: null,
 					latestYStart: null,
@@ -5906,6 +6072,19 @@ define('sequence/themes/Basic',[
 					'line-height': LINE_HEIGHT,
 				},
 			},
+			source: {
+				radius: 2,
+				render: ({x, y, radius}) => {
+					return svg.make('circle', {
+						'cx': x,
+						'cy': y,
+						'r': radius,
+						'fill': '#000000',
+						'stroke': '#000000',
+						'stroke-width': 1,
+					});
+				},
+			},
 			mask: {
 				padding: {
 					top: 0,
@@ -6227,6 +6406,19 @@ define('sequence/themes/Monospace',[
 					'line-height': LINE_HEIGHT,
 				},
 			},
+			source: {
+				radius: 2,
+				render: ({x, y, radius}) => {
+					return svg.make('circle', {
+						'cx': x,
+						'cy': y,
+						'r': radius,
+						'fill': '#000000',
+						'stroke': '#000000',
+						'stroke-width': 1,
+					});
+				},
+			},
 			mask: {
 				padding: {
 					top: 0,
@@ -6547,6 +6739,19 @@ define('sequence/themes/Chunky',[
 					'line-height': LINE_HEIGHT,
 				},
 			},
+			source: {
+				radius: 5,
+				render: ({x, y, radius}) => {
+					return svg.make('circle', {
+						'cx': x,
+						'cy': y,
+						'r': radius,
+						'fill': '#000000',
+						'stroke': '#000000',
+						'stroke-width': 3,
+					});
+				},
+			},
 			mask: {
 				padding: {
 					top: 1,
@@ -7287,6 +7492,19 @@ define('sequence/themes/Sketch',[
 					'line-height': LINE_HEIGHT,
 				},
 			},
+			source: {
+				radius: 1,
+				render: ({x, y, radius}) => {
+					return svg.make('circle', {
+						'cx': x,
+						'cy': y,
+						'r': radius,
+						'fill': '#000000',
+						'stroke': '#000000',
+						'stroke-width': 1,
+					});
+				},
+			},
 			mask: {
 				padding: {
 					top: 0,
@@ -7722,7 +7940,7 @@ define('sequence/themes/Sketch',[
 			);
 			return {
 				shape: svg.make('path', Object.assign({'d': ln.nodes}, attrs)),
-				p1: {x: ln.p1.x - dx1, y: ln.p2.y},
+				p1: {x: ln.p1.x - dx1, y: ln.p1.y},
 				p2: {x: ln.p2.x - dx2, y: ln.p2.y},
 			};
 		}

scripts/editor.js

@@ -56,6 +56,10 @@
 				title: 'Self-connection',
 				code: '{Agent1} -> {Agent1}: {Message}',
 			},
+			{
+				title: 'Found message',
+				code: '* -> {Agent1}: {Message}',
+			},
 			{
 				title: 'Request/response pair',
 				code: (

scripts/sequence/CodeMirrorMode.js

@@ -42,8 +42,13 @@ define(['core/ArrayUtilities'], (array) => {
 			)};
 		}
 
+		const colonTextToEnd = {
+			type: 'operator',
+			suggest: true,
+			then: {'': textToEnd, '\n': hiddenEnd},
+		};
 		const agentListToText = agentListTo({
-			':': {type: 'operator', suggest: true, then: {'': textToEnd}},
+			':': colonTextToEnd,
 		});
 		const agentList2ToText = {type: 'variable', suggest: 'Agent', then: {
 			'': 0,
@@ -53,7 +58,7 @@ define(['core/ArrayUtilities'], (array) => {
 		const singleAgentToText = {type: 'variable', suggest: 'Agent', then: {
 			'': 0,
 			',': CM_ERROR,
-			':': {type: 'operator', suggest: true, then: {'': textToEnd}},
+			':': colonTextToEnd,
 		}};
 		const agentToOptText = {type: 'variable', suggest: 'Agent', then: {
 			'': 0,
@@ -97,7 +102,7 @@ define(['core/ArrayUtilities'], (array) => {
 			};
 		}
 
-		function makeOpBlock(exit) {
+		function makeOpBlock(exit, sourceExit) {
 			const op = {type: 'operator', suggest: true, then: {
 				'+': CM_ERROR,
 				'-': CM_ERROR,
@@ -126,13 +131,13 @@ define(['core/ArrayUtilities'], (array) => {
 					}},
 					'': exit,
 				}},
-				'*': {type: 'operator', suggest: true, then: {
+				'*': {type: 'operator', suggest: true, then: Object.assign({
 					'+': op,
 					'-': op,
 					'*': CM_ERROR,
 					'!': CM_ERROR,
 					'': exit,
-				}},
+				}, sourceExit)},
 				'!': op,
 				'': exit,
 			};
@@ -142,7 +147,10 @@ define(['core/ArrayUtilities'], (array) => {
 			const connect = {
 				type: 'keyword',
 				suggest: true,
-				then: makeOpBlock(agentToOptText),
+				then: makeOpBlock(agentToOptText, {
+					':': colonTextToEnd,
+					'\n': hiddenEnd,
+				}),
 			};
 
 			const then = {'': 0};
@@ -153,7 +161,10 @@ define(['core/ArrayUtilities'], (array) => {
 				override: 'Label',
 				then: {},
 			};
-			return makeOpBlock({type: 'variable', suggest: 'Agent', then});
+			return makeOpBlock(
+				{type: 'variable', suggest: 'Agent', then},
+				then
+			);
 		}
 
 		const BASE_THEN = {

scripts/sequence/Generator.js

@@ -36,8 +36,8 @@ define(['core/ArrayUtilities'], (array) => {
 		equals: (a, b) => {
 			return a.id === b.id;
 		},
-		make: (id, {anchorRight = false} = {}) => {
+		make: (id, {anchorRight = false, isVirtualSource = false} = {}) => {
-			return {id, anchorRight};
+			return {id, anchorRight, isVirtualSource};
 		},
 		indexOf: (list, gAgent) => {
 			return array.indexOf(list, gAgent, GAgent.equals);
@@ -45,6 +45,14 @@ define(['core/ArrayUtilities'], (array) => {
 		hasIntersection: (a, b) => {
 			return array.hasIntersection(a, b, GAgent.equals);
 		},
+		addNearby: (target, reference, item, offset) => {
+			const p = array.indexOf(target, reference, GAgent.equals);
+			if(p === -1) {
+				target.push(item);
+			} else {
+				target.splice(p + offset, 0, item);
+			}
+		},
 	};
 
 	const NOTE_DEFAULT_G_AGENTS = {
@@ -53,6 +61,8 @@ define(['core/ArrayUtilities'], (array) => {
 		'note right': [GAgent.make(']')],
 	};
 
+	const SPECIAL_AGENT_IDS = ['[', ']'];
+
 	const MERGABLE = {
 		'agent begin': {
 			check: ['mode'],
@@ -227,7 +237,7 @@ define(['core/ArrayUtilities'], (array) => {
 			this.activeGroups = new Map();
 			this.gAgents = [];
 			this.labelPattern = null;
-			this.blockCount = 0;
+			this.nextID = 0;
 			this.nesting = [];
 			this.markers = new Set();
 			this.currentSection = null;
@@ -256,7 +266,7 @@ define(['core/ArrayUtilities'], (array) => {
 			this.endGroup = this.endGroup.bind(this);
 		}
 
-		toGAgent({alias, name}) {
+		toGAgent({name, alias, flags}) {
 			if(alias) {
 				if(this.agentAliases.has(name)) {
 					throw new Error(
@@ -275,7 +285,9 @@ define(['core/ArrayUtilities'], (array) => {
 				}
 				this.agentAliases.set(alias, name);
 			}
-			return GAgent.make(this.agentAliases.get(name) || name);
+			return GAgent.make(this.agentAliases.get(name) || name, {
+				isVirtualSource: flags.includes('source'),
+			});
 		}
 
 		addStage(stage, isVisible = true) {
@@ -311,7 +323,12 @@ define(['core/ArrayUtilities'], (array) => {
 		}
 
 		defineGAgents(gAgents) {
-			array.mergeSets(this.currentNest.gAgents, gAgents, GAgent.equals);
+			array.mergeSets(
+				this.currentNest.gAgents,
+				gAgents.filter((gAgent) =>
+					!SPECIAL_AGENT_IDS.includes(gAgent.id)),
+				GAgent.equals
+			);
 			array.mergeSets(this.gAgents, gAgents, GAgent.equals);
 		}
 
@@ -335,7 +352,9 @@ define(['core/ArrayUtilities'], (array) => {
 		validateGAgents(gAgents, {
 			allowGrouped = false,
 			rejectGrouped = false,
+			allowVirtual = false,
 		} = {}) {
+			/* jshint -W074 */ // agent validity checking requires several steps
 			gAgents.forEach((gAgent) => {
 				const state = this.getGAgentState(gAgent);
 				if(state.covered) {
@@ -349,6 +368,9 @@ define(['core/ArrayUtilities'], (array) => {
 				if(state.blocked && (!allowGrouped || state.group === null)) {
 					throw new Error('Duplicate agent name: ' + gAgent.id);
 				}
+				if(!allowVirtual && gAgent.isVirtualSource) {
+					throw new Error('cannot use message source here');
+				}
 				if(gAgent.id.startsWith('__')) {
 					throw new Error(gAgent.id + ' is a reserved name');
 				}
@@ -442,12 +464,18 @@ define(['core/ArrayUtilities'], (array) => {
 			this.replaceGAgentState(rightGAgent, AgentState.LOCKED);
 			this.nesting.push(this.currentNest);
 
-			return {gAgents, stages};
+			return {stages};
 		}
 
 		nextBlockName() {
-			const name = '__BLOCK' + this.blockCount;
+			const name = '__BLOCK' + this.nextID;
-			++ this.blockCount;
+			++ this.nextID;
+			return name;
+		}
+
+		nextVirtualAgentName() {
+			const name = '__' + this.nextID;
+			++ this.nextID;
 			return name;
 		}
 
@@ -651,9 +679,13 @@ define(['core/ArrayUtilities'], (array) => {
 			let ind1 = GAgent.indexOf(this.gAgents, gAgents1[0]);
 			let ind2 = GAgent.indexOf(this.gAgents, gAgents2[0]);
 			if(ind1 === -1) {
-				ind1 = this.gAgents.length;
+				// Virtual sources written as '* -> Ref' will spawn to the left,
+				// not the right (as non-virtual agents would)
+				ind1 = gAgents1[0].isVirtualSource ? -1 : this.gAgents.length;
 			}
 			if(ind2 === -1) {
+				// Virtual and non-virtual agents written as 'Ref -> *' will
+				// spawn to the right
 				ind2 = this.gAgents.length;
 			}
 			if(ind1 === ind2) {
@@ -700,21 +732,79 @@ define(['core/ArrayUtilities'], (array) => {
 			return {beginGAgents, endGAgents, startGAgents, stopGAgents};
 		}
 
+		makeVirtualAgent(anchorRight) {
+			const virtualGAgent = GAgent.make(this.nextVirtualAgentName(), {
+				anchorRight,
+				isVirtualSource: true,
+			});
+			this.replaceGAgentState(virtualGAgent, AgentState.LOCKED);
+			return virtualGAgent;
+		}
+
+		addNearbyAgent(gAgentReference, gAgent, offset) {
+			GAgent.addNearby(
+				this.currentNest.gAgents,
+				gAgentReference,
+				gAgent,
+				offset
+			);
+			GAgent.addNearby(
+				this.gAgents,
+				gAgentReference,
+				gAgent,
+				offset
+			);
+		}
+
+		expandVirtualSourceAgents(gAgents) {
+			if(gAgents[0].isVirtualSource) {
+				if(gAgents[1].isVirtualSource) {
+					throw new Error('Cannot connect found messages');
+				}
+				if(SPECIAL_AGENT_IDS.includes(gAgents[1].id)) {
+					throw new Error(
+						'Cannot connect found messages to special agents'
+					);
+				}
+				const virtualGAgent = this.makeVirtualAgent(true);
+				this.addNearbyAgent(gAgents[1], virtualGAgent, 0);
+				return [virtualGAgent, gAgents[1]];
+			}
+			if(gAgents[1].isVirtualSource) {
+				if(SPECIAL_AGENT_IDS.includes(gAgents[0].id)) {
+					throw new Error(
+						'Cannot connect found messages to special agents'
+					);
+				}
+				const virtualGAgent = this.makeVirtualAgent(false);
+				this.addNearbyAgent(gAgents[0], virtualGAgent, 1);
+				return [gAgents[0], virtualGAgent];
+			}
+			return gAgents;
+		}
+
 		handleConnect({agents, label, options}) {
 			const flags = this.filterConnectFlags(agents);
 
 			let gAgents = agents.map(this.toGAgent);
-			this.validateGAgents(gAgents, {allowGrouped: true});
+			this.validateGAgents(gAgents, {
+				allowGrouped: true,
+				allowVirtual: true,
+			});
 
 			const allGAgents = array.flatMap(gAgents, this.expandGroupedGAgent);
-			this.defineGAgents(allGAgents);
+			this.defineGAgents(allGAgents
+				.filter((gAgent) => !gAgent.isVirtualSource)
+			);
 
 			gAgents = this.expandGroupedGAgentConnection(gAgents);
+			gAgents = this.expandVirtualSourceAgents(gAgents);
 			const agentIDs = gAgents.map((gAgent) => gAgent.id);
 
 			const implicitBeginGAgents = (agents
 				.filter(PAgent.hasFlag('begin', false))
 				.map(this.toGAgent)
+				.filter((gAgent) => !gAgent.isVirtualSource)
 			);
 			this.addStage(this.setGAgentVis(implicitBeginGAgents, true, 'box'));
 
@@ -811,7 +901,7 @@ define(['core/ArrayUtilities'], (array) => {
 			this.agentAliases.clear();
 			this.activeGroups.clear();
 			this.gAgents.length = 0;
-			this.blockCount = 0;
+			this.nextID = 0;
 			this.nesting.length = 0;
 			this.labelPattern = [{token: 'label'}];
 		}

scripts/sequence/Generator_spec.js

@@ -110,6 +110,14 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 	};
 
 	const GENERATED = {
+		agent: (id, {
+			formattedLabel = any(),
+			anchorRight = any(),
+			isVirtualSource = any(),
+		} = {}) => {
+			return {id, formattedLabel, anchorRight, isVirtualSource};
+		},
+
 		beginAgents: (agentIDs, {
 			mode = any(),
 			ln = any(),
@@ -264,8 +272,8 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 		it('includes implicit hidden left/right agents', () => {
 			const sequence = invoke([]);
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('[', {anchorRight: true}),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']', {anchorRight: false}),
 			]);
 		});
 
@@ -296,13 +304,13 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 				PARSED.beginAgents(['E']),
 			]);
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: 'A', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('A'),
-				{id: 'B', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('B'),
-				{id: 'C', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('C'),
-				{id: 'D', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('D'),
-				{id: 'E', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('E'),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
 			]);
 		});
 
@@ -311,10 +319,10 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 				PARSED.connect(['A', 'B']),
 			]);
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: any()},
+				GENERATED.agent('['),
-				{id: 'A', formattedLabel: 'A!', anchorRight: any()},
+				GENERATED.agent('A', {formattedLabel: 'A!'}),
-				{id: 'B', formattedLabel: 'B!', anchorRight: any()},
+				GENERATED.agent('B', {formattedLabel: 'B!'}),
-				{id: ']', formattedLabel: any(), anchorRight: any()},
+				GENERATED.agent(']'),
 			]);
 		});
 
@@ -323,9 +331,9 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 				PARSED.connect([']', 'B']),
 			]);
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: 'B', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('B'),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
 			]);
 		});
 
@@ -335,10 +343,10 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 				PARSED.connect(['A', 'B']),
 			]);
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: 'B', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('B'),
-				{id: 'A', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('A'),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
 			]);
 		});
 
@@ -348,10 +356,10 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 				PARSED.connect(['A', 'B']),
 			]);
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: 'Baz', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('Baz'),
-				{id: 'A', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('A'),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
 			]);
 		});
 
@@ -419,6 +427,119 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 			]);
 		});
 
+		it('converts source agents into virtual agents', () => {
+			const sequence = invoke([
+				PARSED.connect([
+					'A',
+					{name: '', alias: '', flags: ['source']},
+				]),
+			]);
+			expect(sequence.agents).toEqual([
+				GENERATED.agent('['),
+				GENERATED.agent('A'),
+				GENERATED.agent('__0', {
+					anchorRight: false,
+					isVirtualSource: true,
+				}),
+				GENERATED.agent(']'),
+			]);
+			expect(sequence.stages).toEqual([
+				GENERATED.beginAgents(['A']),
+				GENERATED.connect(['A', '__0']),
+				GENERATED.endAgents(['A']),
+			]);
+		});
+
+		it('converts sources into distinct virtual agents', () => {
+			const sequence = invoke([
+				PARSED.connect([
+					'A',
+					{name: '', alias: '', flags: ['source']},
+				]),
+				PARSED.connect([
+					'A',
+					{name: '', alias: '', flags: ['source']},
+				]),
+			]);
+			expect(sequence.agents).toEqual([
+				GENERATED.agent('['),
+				GENERATED.agent('A'),
+				GENERATED.agent('__1'),
+				GENERATED.agent('__0'),
+				GENERATED.agent(']'),
+			]);
+			expect(sequence.stages).toEqual([
+				GENERATED.beginAgents(['A']),
+				GENERATED.connect(['A', '__0']),
+				GENERATED.connect(['A', '__1']),
+				GENERATED.endAgents(['A']),
+			]);
+		});
+
+		it('places source agents near the connected agent', () => {
+			const sequence = invoke([
+				PARSED.beginAgents(['A', 'B', 'C']),
+				PARSED.connect([
+					'B',
+					{name: '', alias: '', flags: ['source']},
+				]),
+			]);
+			expect(sequence.agents).toEqual([
+				GENERATED.agent('['),
+				GENERATED.agent('A'),
+				GENERATED.agent('B'),
+				GENERATED.agent('__0', {
+					anchorRight: false,
+					isVirtualSource: true,
+				}),
+				GENERATED.agent('C'),
+				GENERATED.agent(']'),
+			]);
+		});
+
+		it('places source agents left when connections are reversed', () => {
+			const sequence = invoke([
+				PARSED.beginAgents(['A', 'B', 'C']),
+				PARSED.connect([
+					{name: '', alias: '', flags: ['source']},
+					'B',
+				]),
+			]);
+			expect(sequence.agents).toEqual([
+				GENERATED.agent('['),
+				GENERATED.agent('A'),
+				GENERATED.agent('__0', {
+					anchorRight: true,
+					isVirtualSource: true,
+				}),
+				GENERATED.agent('B'),
+				GENERATED.agent('C'),
+				GENERATED.agent(']'),
+			]);
+		});
+
+		it('rejects connections between virtual agents', () => {
+			expect(() => invoke([
+				PARSED.connect([
+					{name: '', alias: '', flags: ['source']},
+					{name: '', alias: '', flags: ['source']},
+				]),
+			])).toThrow(new Error(
+				'Cannot connect found messages at line 1'
+			));
+		});
+
+		it('rejects connections between virtual agents and sides', () => {
+			expect(() => invoke([
+				PARSED.connect([
+					{name: '', alias: '', flags: ['source']},
+					']',
+				]),
+			])).toThrow(new Error(
+				'Cannot connect found messages to special agents at line 1'
+			));
+		});
+
 		it('uses label patterns for connections', () => {
 			const sequence = invoke([
 				PARSED.labelPattern(['foo ', {token: 'label'}, ' bar']),
@@ -819,12 +940,12 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 			]);
 
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: '__BLOCK0[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK0[', {anchorRight: true}),
-				{id: 'A', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('A'),
-				{id: 'B', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('B'),
-				{id: '__BLOCK0]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK0]', {anchorRight: false}),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
 			]);
 		});
 
@@ -841,20 +962,40 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 			]);
 
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: 'A', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('A'),
-				{id: 'B', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('B'),
-				{id: '__BLOCK0[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK0['),
-				{id: 'C', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('C'),
-				{id: 'D', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('D'),
-				{id: '__BLOCK1[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK1['),
-				{id: 'E', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('E'),
-				{id: 'F', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('F'),
-				{id: '__BLOCK1]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK1]'),
-				{id: '__BLOCK0]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK0]'),
-				{id: 'G', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('G'),
-				{id: 'H', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('H'),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
+			]);
+		});
+
+		it('ignores side agents when calculating block bounds', () => {
+			const sequence = invoke([
+				PARSED.beginAgents(['A', 'B', 'C']),
+				PARSED.blockBegin('if', 'abc'),
+				PARSED.connect(['[', 'B']),
+				PARSED.connect(['B', ']']),
+				PARSED.blockEnd(),
+			]);
+
+			expect(sequence.agents).toEqual([
+				GENERATED.agent('['),
+				GENERATED.agent('A'),
+				GENERATED.agent('__BLOCK0['),
+				GENERATED.agent('B'),
+				GENERATED.agent('__BLOCK0]'),
+				GENERATED.agent('C'),
+				GENERATED.agent(']'),
 			]);
 		});
 
@@ -916,15 +1057,15 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 			]);
 
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: '__BLOCK0[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK0['),
-				{id: '__BLOCK1[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK1['),
-				{id: 'A', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('A'),
-				{id: 'B', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('B'),
-				{id: 'C', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('C'),
-				{id: '__BLOCK1]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK1]'),
-				{id: '__BLOCK0]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK0]'),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
 			]);
 
 			const bounds0 = {
@@ -955,14 +1096,14 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 			]);
 
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: '__BLOCK0[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK0['),
-				{id: '__BLOCK1[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK1['),
-				{id: 'A', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('A'),
-				{id: 'B', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('B'),
-				{id: '__BLOCK1]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK1]'),
-				{id: '__BLOCK0]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK0]'),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
 			]);
 
 			const bounds0 = {
@@ -1051,12 +1192,12 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 			};
 
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: '__BLOCK0[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK0['),
-				{id: 'A', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('A'),
-				{id: 'B', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('B'),
-				{id: '__BLOCK0]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK0]'),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
 			]);
 
 			expect(sequence.stages).toEqual([
@@ -1116,14 +1257,14 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 			]);
 
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: 'A', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('A'),
-				{id: '__BLOCK0[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK0['),
-				{id: 'B', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('B'),
-				{id: 'C', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('C'),
-				{id: '__BLOCK0]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK0]'),
-				{id: 'D', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('D'),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
 			]);
 		});
 
@@ -1135,15 +1276,15 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 			]);
 
 			expect(sequence.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: 'A', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('A'),
-				{id: '__BLOCK0[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK0['),
-				{id: 'B', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('B'),
-				{id: 'C', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('C'),
-				{id: 'D', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('D'),
-				{id: '__BLOCK0]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK0]'),
-				{id: 'E', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('E'),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
 			]);
 		});
 
@@ -1342,16 +1483,16 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 			]);
 
 			expect(sequenceR.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: 'A', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('A'),
-				{id: '__BLOCK1[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK1['),
-				{id: '__BLOCK0[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK0[', {anchorRight: true}),
-				{id: 'B', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('B'),
-				{id: 'C', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('C'),
-				{id: '__BLOCK0]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK0]', {anchorRight: false}),
-				{id: 'D', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('D'),
-				{id: '__BLOCK1]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK1]'),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
 			]);
 
 			const sequenceL = invoke([
@@ -1364,16 +1505,51 @@ defineDescribe('Sequence Generator', ['./Generator'], (Generator) => {
 			]);
 
 			expect(sequenceL.agents).toEqual([
-				{id: '[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('['),
-				{id: '__BLOCK1[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK1['),
-				{id: 'A', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('A'),
-				{id: '__BLOCK0[', formattedLabel: any(), anchorRight: true},
+				GENERATED.agent('__BLOCK0['),
-				{id: 'B', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('B'),
-				{id: 'C', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('C'),
-				{id: '__BLOCK0]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK0]'),
-				{id: '__BLOCK1]', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('__BLOCK1]'),
-				{id: 'D', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent('D'),
-				{id: ']', formattedLabel: any(), anchorRight: false},
+				GENERATED.agent(']'),
+			]);
+		});
+
+		it('allows connections between sources and references', () => {
+			const sequence = invoke([
+				PARSED.beginAgents(['A', 'B', 'C', 'D']),
+				PARSED.groupBegin('Bar', ['B', 'C'], {label: 'Foo'}),
+				PARSED.connect([
+					{name: '', alias: '', flags: ['source']},
+					'Bar',
+				]),
+				PARSED.connect([
+					'Bar',
+					{name: '', alias: '', flags: ['source']},
+				]),
+				PARSED.endAgents(['Bar']),
+			]);
+
+			expect(sequence.agents).toEqual([
+				GENERATED.agent('['),
+				GENERATED.agent('A'),
+				GENERATED.agent('__1', {
+					anchorRight: true,
+					isVirtualSource: true,
+				}),
+				GENERATED.agent('__BLOCK0['),
+				GENERATED.agent('B'),
+				GENERATED.agent('C'),
+				GENERATED.agent('__BLOCK0]'),
+				GENERATED.agent('__2', {
+					anchorRight: false,
+					isVirtualSource: true,
+				}),
+				GENERATED.agent('D'),
+				GENERATED.agent(']'),
 			]);
 		});
 

scripts/sequence/Parser.js

@@ -67,10 +67,10 @@ define([
 	})());
 
 	const CONNECT_AGENT_FLAGS = {
-		'*': 'begin',
+		'*': {flag: 'begin', allowBlankName: true, blankNameFlag: 'source'},
-		'+': 'start',
+		'+': {flag: 'start'},
-		'-': 'stop',
+		'-': {flag: 'stop'},
-		'!': 'end',
+		'!': {flag: 'end'},
 	};
 
 	const TERMINATOR_TYPES = [
@@ -182,7 +182,7 @@ define([
 		return -1;
 	}
 
-	function readAgentAlias(line, start, end, enableAlias) {
+	function readAgentAlias(line, start, end, {enableAlias, allowBlankName}) {
 		let aliasSep = -1;
 		if(enableAlias) {
 			aliasSep = findToken(line, 'as', start);
@@ -190,7 +190,7 @@ define([
 		if(aliasSep === -1 || aliasSep >= end) {
 			aliasSep = end;
 		}
-		if(start >= aliasSep) {
+		if(start >= aliasSep && !allowBlankName) {
 			throw makeError('Missing agent name', errToken(line, start));
 		}
 		return {
@@ -204,25 +204,31 @@ define([
 		aliases = false,
 	} = {}) {
 		const flags = [];
+		const blankNameFlags = [];
 		let p = start;
+		let allowBlankName = false;
 		for(; p < end; ++ p) {
 			const token = line[p];
 			const rawFlag = tokenKeyword(token);
 			const flag = flagTypes[rawFlag];
-			if(flag) {
+			if(!flag) {
-				if(flags.includes(flag)) {
-					throw makeError('Duplicate agent flag: ' + rawFlag, token);
-				}
-				flags.push(flag);
-			} else {
 				break;
 			}
+			if(flags.includes(flag.flag)) {
+				throw makeError('Duplicate agent flag: ' + rawFlag, token);
 			}
-		const {name, alias} = readAgentAlias(line, p, end, aliases);
+			allowBlankName = allowBlankName || Boolean(flag.allowBlankName);
+			flags.push(flag.flag);
+			blankNameFlags.push(flag.blankNameFlag);
+		}
+		const {name, alias} = readAgentAlias(line, p, end, {
+			enableAlias: aliases,
+			allowBlankName,
+		});
 		return {
 			name,
 			alias,
-			flags,
+			flags: name ? flags : blankNameFlags,
 		};
 	}
 

scripts/sequence/Parser_spec.js

@@ -185,6 +185,38 @@ defineDescribe('Sequence Parser', ['./Parser'], (Parser) => {
 			));
 		});
 
+		it('parses source agents', () => {
+			const parsed = parser.parse('A -> *');
+			expect(parsed.stages).toEqual([
+				{
+					type: 'connect',
+					ln: jasmine.anything(),
+					agents: [
+						{name: 'A', alias: '', flags: []},
+						{name: '', alias: '', flags: ['source']},
+					],
+					label: jasmine.anything(),
+					options: jasmine.anything(),
+				},
+			]);
+		});
+
+		it('parses source agents with labels', () => {
+			const parsed = parser.parse('A -> *: foo');
+			expect(parsed.stages).toEqual([
+				{
+					type: 'connect',
+					ln: jasmine.anything(),
+					agents: [
+						{name: 'A', alias: '', flags: []},
+						{name: '', alias: '', flags: ['source']},
+					],
+					label: 'foo',
+					options: jasmine.anything(),
+				},
+			]);
+		});
+
 		it('converts multiple entries', () => {
 			const parsed = parser.parse('A -> B\nB -> A');
 			expect(parsed.stages).toEqual([

scripts/sequence/Renderer.js

@@ -188,6 +188,7 @@ define([
 				theme: this.theme,
 				agentInfos: this.agentInfos,
 				visibleAgentIDs: this.visibleAgentIDs,
+				momentaryAgentIDs: agentIDs,
 				textSizer: this.sizer,
 				addSpacing,
 				addSeparation: this.addSeparation,
@@ -392,6 +393,7 @@ define([
 					id: agent.id,
 					formattedLabel: agent.formattedLabel,
 					anchorRight: agent.anchorRight,
+					isVirtualSource: agent.isVirtualSource,
 					index,
 					x: null,
 					latestYStart: null,

scripts/sequence/components/BaseComponent.js

@@ -13,6 +13,7 @@ define(() => {
 			theme,
 			agentInfos,
 			visibleAgentIDs,
+			momentaryAgentIDs,
 			textSizer,
 			addSpacing,
 			addSeparation,
@@ -25,6 +26,7 @@ define(() => {
 			theme,
 			agentInfos,
 			visibleAgentIDs,
+			momentaryAgentIDs,
 			textSizer,
 			addSpacing,
 			addSeparation,

scripts/sequence/components/Connect.js

@@ -1,8 +1,10 @@
 define([
+	'core/ArrayUtilities',
 	'./BaseComponent',
 	'svg/SVGUtilities',
 	'svg/SVGShapes',
 ], (
+	array,
 	BaseComponent,
 	svg,
 	SVGShapes
@@ -106,6 +108,18 @@ define([
 	];
 
 	class Connect extends BaseComponent {
+		separationPre({agentIDs}, env) {
+			const r = env.theme.connect.source.radius;
+			agentIDs.forEach((id) => {
+				const agentInfo = env.agentInfos.get(id);
+				if(!agentInfo.isVirtualSource) {
+					return;
+				}
+				agentInfo.currentRad = r;
+				agentInfo.currentMaxRad = Math.max(agentInfo.currentMaxRad, r);
+			});
+		}
+
 		separation({label, agentIDs, options}, env) {
 			const config = env.theme.connect;
 
@@ -147,6 +161,8 @@ define([
 					) * 2
 				);
 			}
+
+			array.mergeSets(env.momentaryAgentIDs, agentIDs);
 		}
 
 		renderSelfConnect({label, agentIDs, options}, env) {
@@ -224,14 +240,59 @@ define([
 			);
 		}
 
+		renderSimpleLine(x0, x1, options, env) {
+			const dir = (x0 < x1) ? 1 : -1;
+
+			const config = env.theme.connect;
+			const line = config.line[options.line];
+			const lArrow = ARROWHEADS[options.left];
+			const rArrow = ARROWHEADS[options.right];
+
+			const rendered = line.renderFlat(line.attrs, {
+				x1: x0,
+				dx1: lArrow.lineGap(env.theme, line.attrs) * dir,
+				x2: x1,
+				dx2: -rArrow.lineGap(env.theme, line.attrs) * dir,
+				y: env.primaryY,
+			});
+			env.shapeLayer.appendChild(rendered.shape);
+			return rendered;
+		}
+
+		renderSimpleArrowheads(options, renderedLine, env, dir) {
+			const lArrow = ARROWHEADS[options.left];
+			const rArrow = ARROWHEADS[options.right];
+
+			lArrow.render(env.shapeLayer, env.theme, renderedLine.p1, dir);
+			rArrow.render(env.shapeLayer, env.theme, renderedLine.p2, -dir);
+
+			return {lArrow, rArrow};
+		}
+
+		renderVirtualSources(from, to, renderedLine, env) {
+			const config = env.theme.connect.source;
+
+			if(from.isVirtualSource) {
+				env.shapeLayer.appendChild(config.render({
+					x: renderedLine.p1.x - config.radius,
+					y: renderedLine.p1.y,
+					radius: config.radius,
+				}));
+			}
+			if(to.isVirtualSource) {
+				env.shapeLayer.appendChild(config.render({
+					x: renderedLine.p2.x + config.radius,
+					y: renderedLine.p2.y,
+					radius: config.radius,
+				}));
+			}
+		}
+
 		renderSimpleConnect({label, agentIDs, options}, env) {
 			const config = env.theme.connect;
 			const from = env.agentInfos.get(agentIDs[0]);
 			const to = env.agentInfos.get(agentIDs[1]);
 
-			const lArrow = ARROWHEADS[options.left];
-			const rArrow = ARROWHEADS[options.right];
-
 			const dir = (from.x < to.x) ? 1 : -1;
 
 			const height = (
@@ -257,18 +318,12 @@ define([
 				SVGTextBlockClass: env.SVGTextBlockClass,
 			});
 
-			const line = config.line[options.line];
+			const rendered = this.renderSimpleLine(x0, x1, options, env);
-			const rendered = line.renderFlat(line.attrs, {
+			const {
-				x1: x0,
+				lArrow,
-				dx1: lArrow.lineGap(env.theme, line.attrs) * dir,
+				rArrow
-				x2: x1,
+			} = this.renderSimpleArrowheads(options, rendered, env, dir);
-				dx2: -rArrow.lineGap(env.theme, line.attrs) * dir,
+			this.renderVirtualSources(from, to, rendered, env);
-				y,
-			});
-			env.shapeLayer.appendChild(rendered.shape);
-
-			lArrow.render(env.shapeLayer, env.theme, rendered.p1, dir);
-			rArrow.render(env.shapeLayer, env.theme, rendered.p2, -dir);
 
 			const arrowSpread = Math.max(
 				lArrow.height(env.theme),

scripts/sequence/themes/Basic.js

@@ -150,6 +150,19 @@ define([
 					'line-height': LINE_HEIGHT,
 				},
 			},
+			source: {
+				radius: 2,
+				render: ({x, y, radius}) => {
+					return svg.make('circle', {
+						'cx': x,
+						'cy': y,
+						'r': radius,
+						'fill': '#000000',
+						'stroke': '#000000',
+						'stroke-width': 1,
+					});
+				},
+			},
 			mask: {
 				padding: {
 					top: 0,

scripts/sequence/themes/Chunky.js

@@ -160,6 +160,19 @@ define([
 					'line-height': LINE_HEIGHT,
 				},
 			},
+			source: {
+				radius: 5,
+				render: ({x, y, radius}) => {
+					return svg.make('circle', {
+						'cx': x,
+						'cy': y,
+						'r': radius,
+						'fill': '#000000',
+						'stroke': '#000000',
+						'stroke-width': 3,
+					});
+				},
+			},
 			mask: {
 				padding: {
 					top: 1,

scripts/sequence/themes/Monospace.js

@@ -157,6 +157,19 @@ define([
 					'line-height': LINE_HEIGHT,
 				},
 			},
+			source: {
+				radius: 2,
+				render: ({x, y, radius}) => {
+					return svg.make('circle', {
+						'cx': x,
+						'cy': y,
+						'r': radius,
+						'fill': '#000000',
+						'stroke': '#000000',
+						'stroke-width': 1,
+					});
+				},
+			},
 			mask: {
 				padding: {
 					top: 0,

scripts/sequence/themes/Sketch.js

@@ -139,6 +139,19 @@ define([
 					'line-height': LINE_HEIGHT,
 				},
 			},
+			source: {
+				radius: 1,
+				render: ({x, y, radius}) => {
+					return svg.make('circle', {
+						'cx': x,
+						'cy': y,
+						'r': radius,
+						'fill': '#000000',
+						'stroke': '#000000',
+						'stroke-width': 1,
+					});
+				},
+			},
 			mask: {
 				padding: {
 					top: 0,
@@ -574,7 +587,7 @@ define([
 			);
 			return {
 				shape: svg.make('path', Object.assign({'d': ln.nodes}, attrs)),
-				p1: {x: ln.p1.x - dx1, y: ln.p2.y},
+				p1: {x: ln.p1.x - dx1, y: ln.p1.y},
 				p2: {x: ln.p2.x - dx2, y: ln.p2.y},
 			};
 		}