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Refactor RescopeGlobalSymbols to move the externs rewriting to the sa…
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…me traversal as the source-variable rewriting.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=152212804
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@dimvar
dimvar authored and Tyler Breisacher committed Apr 6, 2017
1 parent a618d06 commit 0b33297
Showing 1 changed file with 57 additions and 71 deletions.
128 changes: 57 additions & 71 deletions src/com/google/javascript/jscomp/RescopeGlobalSymbols.java
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Expand Up @@ -130,6 +130,14 @@ private boolean isCrossModuleName(String name) {
|| compiler.getCodingConvention().isExported(name, false); || compiler.getCodingConvention().isExported(name, false);
} }


private static boolean isExternVar(String varname, NodeTraversal t) {
if (varname.isEmpty()) {
return false;
}
Var v = t.getScope().getVar(varname);
return v == null || v.isExtern();
}

private void addExternForGlobalSymbolNamespace() { private void addExternForGlobalSymbolNamespace() {
Node varNode = IR.var(IR.name(globalSymbolNamespace)); Node varNode = IR.var(IR.name(globalSymbolNamespace));
CompilerInput input = compiler.getSynthesizedExternsInput(); CompilerInput input = compiler.getSynthesizedExternsInput();
Expand All @@ -143,36 +151,32 @@ public void process(Node externs, Node root) {
if (addExtern) { if (addExtern) {
addExternForGlobalSymbolNamespace(); addExternForGlobalSymbolNamespace();
} }
// Rewrite all references to global symbols to properties of a
// single symbol by: // Rewrite all references to global symbols to properties of a single symbol:
// (If necessary the 4 traversals could be combined. They are left
// separate for readability reasons.) // Turn global named function statements into var assignments.
// 1. turning global named function statements into var assignments.
NodeTraversal.traverseEs6( NodeTraversal.traverseEs6(
compiler, compiler,
root, root,
new RewriteGlobalFunctionStatementsToVarAssignmentsCallback()); new RewriteGlobalFunctionStatementsToVarAssignmentsCallback());
// 2. find global names that are used in more than one module. Those that
// are have to be rewritten. // Find global names that are used in more than one module. Those that
// are have to be rewritten.
List<Callback> nonMutatingPasses = new ArrayList<>(); List<Callback> nonMutatingPasses = new ArrayList<>();
nonMutatingPasses.add(new FindCrossModuleNamesCallback()); nonMutatingPasses.add(new FindCrossModuleNamesCallback());
// and find names that may refering functions that reference this.
// And find names that may refer to functions that reference this.
nonMutatingPasses.add(new FindNamesReferencingThis()); nonMutatingPasses.add(new FindNamesReferencingThis());
CombinedCompilerPass.traverse(compiler, root, nonMutatingPasses); CombinedCompilerPass.traverse(compiler, root, nonMutatingPasses);
// 3. rewriting all references to be property accesses of the single symbol.
// Rewrite all references to be property accesses of the single symbol.
RewriteScopeCallback rewriteScope = new RewriteScopeCallback(); RewriteScopeCallback rewriteScope = new RewriteScopeCallback();
NodeTraversal.traverseEs6(compiler, root, rewriteScope); NodeTraversal.traverseEs6(compiler, root, rewriteScope);
// 4. removing the var from statements in global scope if the declared names
// have been rewritten in the previous pass. // Remove the var from statements in global scope if the declared names have been rewritten
// in the previous pass.
NodeTraversal.traverseEs6(compiler, root, new RemoveGlobalVarCallback()); NodeTraversal.traverseEs6(compiler, root, new RemoveGlobalVarCallback());
rewriteScope.declareModuleGlobals(); rewriteScope.declareModuleGlobals();

// Extra pass which makes all extern global symbols reference window
// explicitly.
NodeTraversal.traverseEs6(
compiler,
root,
new MakeExternsReferenceWindowExplicitly());
} }


/** /**
Expand Down Expand Up @@ -287,8 +291,8 @@ public void visit(NodeTraversal t, Node n, Node parent) {


/** /**
* Visits each NAME token and checks whether it refers to a global variable. * Visits each NAME token and checks whether it refers to a global variable.
* If yes, rewrites the name to be a property access on the * If yes, rewrites the name to be a property access on the "globalSymbolNamespace".
* "globalSymbolNamespace". * If the NAME is an extern variable, it becomes a property access on window.
* *
* <pre>var a = 1, b = 2, c = 3;</pre> * <pre>var a = 1, b = 2, c = 3;</pre>
* becomes * becomes
Expand All @@ -302,11 +306,9 @@ public void visit(NodeTraversal t, Node n, Node parent) {
* <pre>a()</pre> * <pre>a()</pre>
* becomes * becomes
* <pre>(0,NS.a)()</pre> * <pre>(0,NS.a)()</pre>
* Notice the special syntax here to preserve the *this* semantics in the * Notice the special syntax here to preserve the *this* semantics in the function call.
* function call.
*/ */
private class RewriteScopeCallback extends AbstractPostOrderCallback { private class RewriteScopeCallback extends AbstractPostOrderCallback {

List<ModuleGlobal> preDeclarations = new ArrayList<>(); List<ModuleGlobal> preDeclarations = new ArrayList<>();


@Override @Override
Expand All @@ -319,22 +321,18 @@ public void visit(NodeTraversal t, Node n, Node parent) {
if (parent.isFunction() && name.isEmpty()) { if (parent.isFunction() && name.isEmpty()) {
return; return;
} }
Var var = t.getScope().getVar(name); if (isExternVar(name, t)) {
if (var == null) { visitExtern(n, parent);
return;
}
// Don't touch externs.
if (var.isExtern()) {
return; return;
} }
// When the globalSymbolNamespace is used as a local variable name // When the globalSymbolNamespace is used as a local variable name
// add suffix to avoid shadowing the namespace. Also add a suffix // add suffix to avoid shadowing the namespace. Also add a suffix
// if a name starts with the name of the globalSymbolNamespace and // if a name starts with the name of the globalSymbolNamespace and
// the suffix. // the suffix.
if (!var.isExtern() && !var.isGlobal() Var var = t.getScope().getVar(name);
if (!var.isGlobal()
&& (name.equals(globalSymbolNamespace) && (name.equals(globalSymbolNamespace)
|| name.startsWith( || name.startsWith(globalSymbolNamespace + DISAMBIGUATION_SUFFIX))) {
globalSymbolNamespace + DISAMBIGUATION_SUFFIX))) {
n.setString(name + DISAMBIGUATION_SUFFIX); n.setString(name + DISAMBIGUATION_SUFFIX);
compiler.reportCodeChange(); compiler.reportCodeChange();
} }
Expand All @@ -344,8 +342,7 @@ public void visit(NodeTraversal t, Node n, Node parent) {
} }
Node nameNode = var.getNameNode(); Node nameNode = var.getNameNode();
// The exception variable (e in try{}catch(e){}) should not be rewritten. // The exception variable (e in try{}catch(e){}) should not be rewritten.
if (nameNode != null && nameNode.getParent() != null if (nameNode != null && nameNode.getParent() != null && nameNode.getParent().isCatch()) {
&& nameNode.getParent().isCatch()) {
return; return;
} }
replaceSymbol(n, name, t.getInput()); replaceSymbol(n, name, t.getInput());
Expand All @@ -360,18 +357,15 @@ private void replaceSymbol(Node node, String name, CompilerInput input) {
if (!parent.isVar()) { if (!parent.isVar()) {
return; return;
} }
// If it is a var declaration, but no cross module names are declared boolean hasInterestingChildren = false;
// we also don't have to do anything.
boolean hasCrossModuleChildren = false;
for (Node c : parent.children()) { for (Node c : parent.children()) {
// Var child is no longer a name means it was transformed already // VAR child is no longer a name means it was transformed already.
// which means there was a cross module name.
if (!c.isName() || isCrossModuleName(c.getString())) { if (!c.isName() || isCrossModuleName(c.getString())) {
hasCrossModuleChildren = true; hasInterestingChildren = true;
break; break;
} }
} }
if (!hasCrossModuleChildren) { if (!hasInterestingChildren) {
return; return;
} }
} }
Expand Down Expand Up @@ -411,6 +405,27 @@ private void replaceSymbol(Node node, String name, CompilerInput input) {
compiler.reportCodeChange(); compiler.reportCodeChange();
} }


/**
* Rewrites extern names to be explicit children of window instead of only implicitly
* referencing it. This enables injecting window into a scope and make all global symbols
* depend on the injected object.
*/
private void visitExtern(Node nameNode, Node parent) {
String name = nameNode.getString();
if (globalSymbolNamespace.equals(name) || SPECIAL_EXTERNS.contains(name)) {
return;
}
Node windowPropAccess = IR.getprop(IR.name(WINDOW), IR.string(name));
if (parent.isVar() && nameNode.hasOneChild()) {
Node assign = IR.assign(windowPropAccess, nameNode.getFirstChild().detachFromParent());
assign.setJSDocInfo(parent.getJSDocInfo());
parent.replaceChild(nameNode, assign.srcrefTree(parent));
} else {
parent.replaceChild(nameNode, windowPropAccess.srcrefTree(nameNode));
}
compiler.reportCodeChange();
}

/** /**
* Adds back declarations for variables that do not cross module boundaries. * Adds back declarations for variables that do not cross module boundaries.
* Must be called after RemoveGlobalVarCallback. * Must be called after RemoveGlobalVarCallback.
Expand All @@ -421,8 +436,7 @@ void declareModuleGlobals() {
&& global.root.getFirstChild().isVar()) { && global.root.getFirstChild().isVar()) {
global.root.getFirstChild().addChildToBack(global.name); global.root.getFirstChild().addChildToBack(global.name);
} else { } else {
global.root.addChildToFront( global.root.addChildToFront(IR.var(global.name).srcref(global.name));
IR.var(global.name).srcref(global.name));
} }
compiler.reportCodeChange(); compiler.reportCodeChange();
} }
Expand Down Expand Up @@ -515,32 +529,4 @@ private Node joinOnComma(List<Node> commas, Node source) {
return comma; return comma;
} }
} }

/**
* Rewrites extern names to be explicit children of window instead of only
* implicitly referencing it.
* This enables injecting window into a scope and make all global symbol
* depend on the injected object.
*/
private class MakeExternsReferenceWindowExplicitly extends
AbstractPostOrderCallback {

@Override
public void visit(NodeTraversal t, Node n, Node parent) {
if (!n.isName()) {
return;
}
String name = n.getString();
if (globalSymbolNamespace.equals(name)
|| SPECIAL_EXTERNS.contains(name)) {
return;
}
Var var = t.getScope().getVar(name);
if (name.length() > 0 && (var == null || var.isExtern())) {
parent.replaceChild(n, IR.getprop(IR.name(WINDOW), IR.string(name))
.srcrefTree(n));
compiler.reportCodeChange();
}
}
}
} }

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