Trace primitive values through variables

src/ast/nodes/Identifier.ts

@@ -1,6 +1,6 @@
 import { Node, NodeBase } from './shared/Node';
 import isReference from 'is-reference';
-import { ObjectPath, UNKNOWN_EXPRESSION } from '../values';
+import { ObjectPath, UNKNOWN_EXPRESSION, UNKNOWN_VALUE } from '../values';
 import ExecutionPathOptions from '../ExecutionPathOptions';
 import Variable from '../variables/Variable';
 import CallOptions from '../CallOptions';
@@ -72,6 +72,13 @@ export default class Identifier extends NodeBase {
 		}
 	}
 
+	getPrimitiveValue() {
+		if (this.variable !== null) {
+			return this.variable.getPrimitiveValue();
+		}
+		return UNKNOWN_VALUE;
+	}
+
 	hasEffectsWhenAccessedAtPath(path: ObjectPath, options: ExecutionPathOptions): boolean {
 		return this.variable && this.variable.hasEffectsWhenAccessedAtPath(path, options);
 	}

src/ast/nodes/IfStatement.ts

@@ -51,7 +51,7 @@ export default class IfStatement extends StatementBase {
 
 	render(code: MagicString, options: RenderOptions) {
 		// Note that unknown test values are always included
-		const testValue = this.hasUnknownTestValue ? UNKNOWN_VALUE : this.test.getPrimitiveValue([]);
+		const testValue = this.hasUnknownTestValue ? UNKNOWN_VALUE : this.test.getPrimitiveValue();
 		if (
 			!this.test.included &&
 			(testValue ? this.alternate === null || !this.alternate.included : !this.consequent.included)

src/ast/variables/LocalVariable.ts

@@ -9,7 +9,7 @@ import {
 	ForEachReturnExpressionCallback,
 	SomeReturnExpressionCallback
 } from '../nodes/shared/Expression';
-import { ObjectPath } from '../values';
+import { ObjectPath, UNKNOWN_VALUE } from '../values';
 import { Node } from '../nodes/shared/Node';
 import { NodeType } from '../nodes/NodeType';
 
@@ -57,6 +57,13 @@ export default class LocalVariable extends Variable {
 		}
 	}
 
+	getPrimitiveValue() {
+		if (!this.init || this.reassignments.isPathReassigned([])) {
+			return UNKNOWN_VALUE;
+		}
+		return this.init.getPrimitiveValue();
+	}
+
 	hasEffectsWhenAccessedAtPath(path: ObjectPath, options: ExecutionPathOptions) {
 		if (path.length === 0) return false;
 		return (

src/ast/variables/ReplaceableInitializationVariable.ts

@@ -1,5 +1,5 @@
 import LocalVariable from './LocalVariable';
-import { ObjectPath, UNKNOWN_EXPRESSION } from '../values';
+import { ObjectPath, UNKNOWN_EXPRESSION, UNKNOWN_VALUE } from '../values';
 import ExecutionPathOptions from '../ExecutionPathOptions';
 import CallOptions from '../CallOptions';
 import Identifier from '../nodes/Identifier';
@@ -10,6 +10,10 @@ export default class ReplaceableInitializationVariable extends LocalVariable {
 		super(name, declarator, null);
 	}
 
+	getPrimitiveValue() {
+		return UNKNOWN_VALUE;
+	}
+
 	hasEffectsWhenAccessedAtPath(path: ObjectPath, options: ExecutionPathOptions) {
 		return (
 			this._getInit(options).hasEffectsWhenAccessedAtPath(path, options) ||

test/form/samples/dynamic-resolvable-if-statements/_config.js

@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'allows using variables to resolve conditionals'
+};

test/form/samples/dynamic-resolvable-if-statements/_expected/amd.js

@@ -0,0 +1,7 @@
+define(function () { 'use strict';
+
+	{
+		console.log('retained');
+	}
+
+});

test/form/samples/dynamic-resolvable-if-statements/_expected/cjs.js

@@ -0,0 +1,5 @@
+'use strict';
+
+{
+	console.log('retained');
+}

test/form/samples/dynamic-resolvable-if-statements/_expected/es.js

@@ -0,0 +1,3 @@
+{
+	console.log('retained');
+}

test/form/samples/dynamic-resolvable-if-statements/_expected/iife.js

@@ -0,0 +1,8 @@
+(function () {
+	'use strict';
+
+	{
+		console.log('retained');
+	}
+
+}());

test/form/samples/dynamic-resolvable-if-statements/_expected/system.js

@@ -0,0 +1,12 @@
+System.register([], function (exports, module) {
+	'use strict';
+	return {
+		execute: function () {
+
+			{
+				console.log('retained');
+			}
+
+		}
+	};
+});

test/form/samples/dynamic-resolvable-if-statements/_expected/umd.js

@@ -0,0 +1,11 @@
+(function (global, factory) {
+	typeof exports === 'object' && typeof module !== 'undefined' ? factory() :
+	typeof define === 'function' && define.amd ? define(factory) :
+	(factory());
+}(this, (function () { 'use strict';
+
+	{
+		console.log('retained');
+	}
+
+})));

test/form/samples/dynamic-resolvable-if-statements/main.js

@@ -0,0 +1,7 @@
+const value = true;
+
+if (value) {
+	console.log('retained');
+} else {
+	console.log('removed');
+}

test/form/samples/side-effect-p/_expected/amd.js

@@ -1,10 +1,8 @@
 define(function () { 'use strict';
 
-	var bool = true;
-
 	const hs = document.documentElement.style;
 
-	if ( bool ) {
+	{
 		hs.color = "#222";
 	}
 

test/form/samples/side-effect-p/_expected/cjs.js

@@ -1,9 +1,7 @@
 'use strict';
 
-var bool = true;
-
 const hs = document.documentElement.style;
 
-if ( bool ) {
+{
 	hs.color = "#222";
 }

test/form/samples/side-effect-p/_expected/es.js

@@ -1,7 +1,5 @@
-var bool = true;
-
 const hs = document.documentElement.style;
 
-if ( bool ) {
+{
 	hs.color = "#222";
 }

test/form/samples/side-effect-p/_expected/iife.js

@@ -1,11 +1,9 @@
 (function () {
 	'use strict';
 
-	var bool = true;
-
 	const hs = document.documentElement.style;
 
-	if ( bool ) {
+	{
 		hs.color = "#222";
 	}
 

test/form/samples/side-effect-p/_expected/system.js

@@ -3,11 +3,9 @@ System.register([], function (exports, module) {
 	return {
 		execute: function () {
 
-			var bool = true;
-
 			const hs = document.documentElement.style;
 
-			if ( bool ) {
+			{
 				hs.color = "#222";
 			}
 

test/form/samples/side-effect-p/_expected/umd.js

@@ -4,11 +4,9 @@
 	(factory());
 }(this, (function () { 'use strict';
 
-	var bool = true;
-
 	const hs = document.documentElement.style;
 
-	if ( bool ) {
+	{
 		hs.color = "#222";
 	}