From 25ca424c2a987718e6472a67e0e6847ea13d680f Mon Sep 17 00:00:00 2001
From: Rich-Harris <richard.a.harris@gmail.com>
Date: Sun, 20 Sep 2015 19:32:03 -0400
Subject: [PATCH] mark side-effecty statements (call expressions and
 assignments to globals) - fixes #112

---
 src/Bundle.js    |  5 +++++
 src/Module.js    |  6 ++++++
 src/Statement.js | 19 +++++++++++++++++++
 3 files changed, 30 insertions(+)

diff --git a/src/Bundle.js b/src/Bundle.js
index 48ca4c3..28347b1 100644
--- a/src/Bundle.js
+++ b/src/Bundle.js
@@ -67,6 +67,11 @@ export default class Bundle {
 				entryModule.markAllStatements( true );
 				entryModule.markAllExports();
 
+				// Include all side-effects
+				this.modules.forEach( module => {
+					module.markAllSideEffects();
+				});
+
 				// Sort the modules.
 				this.orderedModules = this.sort();
 
diff --git a/src/Module.js b/src/Module.js
index 18f9628..17810a8 100644
--- a/src/Module.js
+++ b/src/Module.js
@@ -437,6 +437,12 @@ export default class Module {
 		this.markAllExports();
 	}
 
+	markAllSideEffects () {
+		this.statements.forEach( statement => {
+			if ( statement.hasSideEffects ) statement.mark();
+		});
+	}
+
 	markAllStatements ( isEntryModule ) {
 		this.statements.forEach( statement => {
 			if ( statement.isIncluded ) return; // TODO can this happen? probably not...
diff --git a/src/Statement.js b/src/Statement.js
index 91c14aa..fad15ad 100644
--- a/src/Statement.js
+++ b/src/Statement.js
@@ -8,6 +8,11 @@ const blockDeclarations = {
 	'let': true
 };
 
+const modifierNodes = {
+	AssignmentExpression: 'left',
+	UpdateExpression: 'argument'
+};
+
 function isIife ( node, parent ) {
 	return parent && parent.type === 'CallExpression' && node === parent.callee;
 }
@@ -47,6 +52,7 @@ export default class Statement {
 		this.dependantIds = [];
 		this.namespaceReplacements = [];
 
+		this.hasSideEffects = false;
 		this.isIncluded = false;
 
 		this.isImportDeclaration = node.type === 'ImportDeclaration';
@@ -167,6 +173,19 @@ export default class Statement {
 					if ( isFunctionDeclaration( node, parent ) ) writeDepth += 1;
 					if ( /Function/.test( node.type ) && !isIife( node, parent ) ) readDepth += 1;
 
+					// If this is a top-level call expression, or an assignment to a global,
+					// this statement will need to be marked
+					if ( !readDepth ) {
+						if ( node.type === 'CallExpression' ) {
+							this.hasSideEffects = true;
+						} else if ( node.type in modifierNodes ) {
+							let subject = node[ modifierNodes[ node.type ] ];
+							while ( subject.type === 'MemberExpression' ) subject = subject.object;
+
+							if ( !this.module.locals.defines( subject.name ) ) this.hasSideEffects = true;
+						}
+					}
+
 					if ( node._scope ) scope = node._scope;
 
 					this.checkForReads( scope, node, parent, !readDepth );