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Improve CommonJS UMD pattern detection.
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Checks to see if the enclosing "if" test references the "module" or "define" names.
Prevents exports nested in IF clauses from being always detected as a UMD pattern when they may just be performing a conditional export.

Closes #2963

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=199227525
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@ChadKillingsworth @tjgq
ChadKillingsworth authored and tjgq committed Jun 5, 2018
1 parent dbc0888 commit 9009ecb
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Showing 2 changed files with 77 additions and 24 deletions.
80 changes: 59 additions & 21 deletions src/com/google/javascript/jscomp/ProcessCommonJSModules.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -334,10 +334,16 @@ static class UmdPattern {
static class ExportInfo {
final Node node;
final Scope scope;
final boolean isInSupportedScope;

ExportInfo(Node node, Scope scope) {
this.node = node;
this.scope = scope;

Node disqualifyingParent =
NodeUtil.getEnclosingNode(
node, (n) -> n.isIf() || n.isHook() || n.isFunction() || n.isArrowFunction());
this.isInSupportedScope = disqualifyingParent == null;
}
}

Expand Down Expand Up @@ -575,10 +581,9 @@ public void visit(NodeTraversal t, Node n, Node parent) {
moduleExports.add(new ExportInfo(n, t.getScope()));

// If the module.exports statement is nested in the then branch of an if statement,
// and the test of the if checks for "module" or "define,
// assume the if statement is an UMD pattern with a common js export in the then branch
// This seems fragile but has worked well for a long time.
// TODO(ChadKillingsworth): Discover if there is a better way to detect these.
Node ifAncestor = getOutermostIfAncestor(parent);
Node ifAncestor = getOutermostUmdTest(parent);
if (ifAncestor != null && (NodeUtil.isLValue(n) || isInIfTest(n))) {
UmdPattern existingPattern = findUmdPattern(umdPatterns, ifAncestor);
if (existingPattern != null) {
Expand All @@ -598,11 +603,10 @@ public boolean apply(Node node) {
}
} else if (n.matchesQualifiedName("define.amd")) {
// If a define.amd statement is nested in the then branch of an if statement,
// and the test of the if checks for "module" or "define,
// assume the if statement is an UMD pattern with a common js export
// in the else branch
// This seems fragile but has worked well for a long time.
// TODO(ChadKillingsworth): Discover if there is a better way to detect these.
Node ifAncestor = getOutermostIfAncestor(parent);
Node ifAncestor = getOutermostUmdTest(parent);
if (ifAncestor != null
&& findUmdPattern(umdPatterns, ifAncestor) == null
&& (NodeUtil.isLValue(n) || isInIfTest(n))) {
Expand Down Expand Up @@ -635,10 +639,9 @@ && findUmdPattern(umdPatterns, ifAncestor) == null
exports.add(new ExportInfo(n, t.getScope()));

// If the exports statement is nested in the then branch of an if statement,
// and the test of the if checks for "module" or "define,
// assume the if statement is an UMD pattern with a common js export in the then branch
// This seems fragile but has worked well for a long time.
// TODO(ChadKillingsworth): Discover if there is a better way to detect these.
Node ifAncestor = getOutermostIfAncestor(parent);
Node ifAncestor = getOutermostUmdTest(parent);
if (ifAncestor != null
&& findUmdPattern(umdPatterns, ifAncestor) == null
&& (NodeUtil.isLValue(n) || isInIfTest(n))) {
Expand Down Expand Up @@ -848,8 +851,11 @@ boolean initializeModule() {
return directAssignments < 2;
}

/** Find the outermost if node ancestor for a node without leaving the function scope */
private Node getOutermostIfAncestor(Node n) {
/**
* Find the outermost if node ancestor for a node without leaving the function scope. To match,
* the test class of the "if" statement must reference "module" or "define" names.
*/
private Node getOutermostUmdTest(Node n) {
if (n == null || NodeUtil.isTopLevel(n) || n.isFunction()) {
return null;
}
Expand All @@ -861,15 +867,37 @@ private Node getOutermostIfAncestor(Node n) {
// When walking up ternary operations (hook), don't check if parent is the condition,
// because one ternary operation can be then/else branch of another.
if (parent.isIf() || parent.isHook()) {
Node outerIf = getOutermostIfAncestor(parent);
Node outerIf = getOutermostUmdTest(parent);
if (outerIf != null) {
return outerIf;
}

return parent;
final List<Node> umdTests = new ArrayList<>();
NodeUtil.visitPreOrder(
parent.getFirstChild(),
new NodeUtil.Visitor() {
@Override
public void visit(Node node) {
if (node.isName()
&& (node.getString().equals(MODULE) || node.getString().equals("define"))) {
umdTests.add(node);
}
}
});

// Webpack replaces tests of `typeof module !== 'undefined'` with `true`
if (umdTests.isEmpty() && parent.getFirstChild().isTrue()) {
umdTests.add(parent.getFirstChild());
}

if (!umdTests.isEmpty()) {
return parent;
}

return null;
}

return getOutermostIfAncestor(parent);
return getOutermostUmdTest(parent);
}

/** Return whether the node is within the test portion of an if statement */
Expand Down Expand Up @@ -1350,7 +1378,8 @@ private void visitExport(NodeTraversal t, ExportInfo export) {
&& root.getParent().getParent().isExprResult()
&& rValueVar != null
&& (NodeUtil.getEnclosingScript(rValueVar.nameNode) == null
|| (rValueVar.nameNode.getParent() != null && !rValueVar.isParam()))) {
|| (rValueVar.nameNode.getParent() != null && !rValueVar.isParam()))
&& export.isInSupportedScope) {
root.getParent().getParent().detach();
t.reportCodeChange();
return;
Expand Down Expand Up @@ -1388,7 +1417,8 @@ private void visitExport(NodeTraversal t, ExportInfo export) {
} else if (root.getNext() != null
&& root.getNext().isName()
&& rValueVar != null
&& rValueVar.isGlobal()) {
&& rValueVar.isGlobal()
&& export.isInSupportedScope) {
// This is a where a module export assignment is used in a complex expression.
// Before: `SOME_VALUE !== undefined && module.exports = SOME_VALUE`
// After: `SOME_VALUE !== undefined && module$name`
Expand Down Expand Up @@ -1808,10 +1838,11 @@ private String getExportedName(NodeTraversal t, Node n, Var var) {

Node exportedName = getExportedNameNode(export);
// We don't want to handle the export itself
if (exportRValue == n
|| ((NodeUtil.isClassExpression(exportRValue)
|| NodeUtil.isFunctionExpression(exportRValue))
&& exportedName == n)) {
if (export.isInSupportedScope
&& (exportRValue == n
|| ((NodeUtil.isClassExpression(exportRValue)
|| NodeUtil.isFunctionExpression(exportRValue))
&& exportedName == n))) {
return null;
}

Expand Down Expand Up @@ -1858,9 +1889,16 @@ private String getExportedName(NodeTraversal t, Node n, Var var) {
key = key.getNext();
}
if (key != null && keyIsExport) {
return baseExportName + "." + key.getString();
if (export.isInSupportedScope) {
return baseExportName + "." + key.getString();
} else {
return n.getQualifiedName();
}
}
} else {
if (!export.isInSupportedScope) {
return n.getQualifiedName();
}
if (var.getNameNode() == exportedName) {
String exportPrefix;
if (exportBaseQName.startsWith(MODULE)) {
Expand Down
21 changes: 18 additions & 3 deletions test/com/google/javascript/jscomp/ProcessCommonJSModulesTest.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -694,7 +694,8 @@ public void testUMDRemoveIIFE() {
lines(
"/** @const */ var module$test = {};",
"(function(){",
" /** @const */ module$test.default={foo:'bar'};",
" var foobar = {foo: 'bar'};",
" /** @const */ module$test.default=foobar;",
"}).call(window);"));

// Can't remove IIFEs when there are sibling statements
Expand All @@ -714,7 +715,8 @@ public void testUMDRemoveIIFE() {
lines(
"/** @const */ var module$test = {};",
"(function(){",
" /** @const */ module$test.default={foo:\"bar\"};",
" var foobar = {foo: 'bar'};",
" /** @const */ module$test.default = foobar;",
"})();",
"alert('foo');"));

Expand All @@ -736,7 +738,8 @@ public void testUMDRemoveIIFE() {
"/** @const */ var module$test = {};",
"alert('foo');",
"(function(){",
" /** @const */ module$test.default={foo:\"bar\"};",
" var foobar={foo:\"bar\"};",
" /** @const */ module$test.default=foobar;",
"})();"));

// Annotations for local names should be preserved
Expand Down Expand Up @@ -1208,4 +1211,16 @@ public void testWebpackAMDModuleShim() {
" function(module) { return module; };")));
test(inputs, expecteds);
}

public void testUMDRequiresIfTest() {
testModules(
"test.js",
lines("var foobar = {foo: 'bar'}; if (foobar) { module.exports = foobar; }"),
lines(
"/** @const */ var module$test = {};",
"var foobar$$module$test={foo:\"bar\"};",
"if(foobar$$module$test) {",
" /** @const */ module$test.default = foobar$$module$test;",
"}"));
}
}

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