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In ES6RewriteDestructuring visitArrayPattern, if the parent of the de…
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…structuring assignment is not an expr result, for example, a for loop or another assignment, then transformed the destructuring assignment into an arrow function whose result is the original destructuring assignment.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=158769794
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@EatingW
EatingW authored and Tyler Breisacher committed Jun 13, 2017
1 parent 481ef6f commit 1ea642a
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Showing 5 changed files with 399 additions and 17 deletions.
77 changes: 61 additions & 16 deletions src/com/google/javascript/jscomp/Es6RewriteDestructuring.java
View file
Expand Up @@ -53,6 +53,9 @@ public void hotSwapScript(Node scriptRoot, Node originalRoot) {
@Override
public boolean shouldTraverse(NodeTraversal t, Node n, Node parent) {
switch (n.getToken()) {
case FUNCTION:
visitFunction(t, n);
break;
case PARAM_LIST:
visitParamList(t, n, parent);
break;
Expand Down Expand Up @@ -82,6 +85,19 @@ public void visit(NodeTraversal t, Node n, Node parent) {
}
}

/**
* If the function is an arrow function, wrap the body in a block if it is not already a block.
*/
private void visitFunction(NodeTraversal t, Node function) {
Node body = function.getLastChild();
if (!body.isNormalBlock()) {
body.detach();
Node replacement = IR.block(IR.returnNode(body)).useSourceInfoIfMissingFromForTree(body);
function.addChildToBack(replacement);
t.reportCodeChange();
}
}

/**
* Processes trailing default and rest parameters.
*/
Expand Down Expand Up @@ -203,7 +219,8 @@ private void visitForOf(Node node) {
}

private void visitObjectPattern(NodeTraversal t, Node objectPattern, Node parent) {
Node rhs, nodeToDetach;
Node rhs;
Node nodeToDetach;
if (NodeUtil.isNameDeclaration(parent) && !NodeUtil.isEnhancedFor(parent.getParent())) {
rhs = objectPattern.getNext();
nodeToDetach = parent;
Expand Down Expand Up @@ -244,7 +261,8 @@ private void visitObjectPattern(NodeTraversal t, Node objectPattern, Node parent
for (Node child = objectPattern.getFirstChild(), next; child != null; child = next) {
next = child.getNext();

Node newLHS, newRHS;
Node newLHS;
Node newRHS;
if (child.isStringKey()) {
if (!child.hasChildren()) { // converting shorthand
Node name = IR.name(child.getString());
Expand Down Expand Up @@ -314,35 +332,35 @@ private void visitObjectPattern(NodeTraversal t, Node objectPattern, Node parent
}

private void visitArrayPattern(NodeTraversal t, Node arrayPattern, Node parent) {
Node rhs, nodeToDetach;
if (NodeUtil.isNameDeclaration(parent) && !NodeUtil.isEnhancedFor(parent.getParent())) {
rhs = arrayPattern.getNext();
nodeToDetach = parent;
replaceArrayPattern(t, arrayPattern, arrayPattern.getNext(), parent, parent);
} else if (parent.isAssign()) {
rhs = arrayPattern.getNext();
nodeToDetach = parent.getParent();
Preconditions.checkState(nodeToDetach.isExprResult());
if (parent.getParent().isExprResult()) {
replaceArrayPattern(t, arrayPattern, arrayPattern.getNext(), parent, parent.getParent());
} else {
wrapAssignmentInCallToArrow(t, parent);
}
} else if (parent.isArrayPattern()
|| parent.isRest()
|| parent.isDefaultValue()
|| parent.isStringKey()) {
// This is a nested array pattern. Don't do anything now; we'll visit it
// after visiting the parent.
return;
} else if (NodeUtil.isEnhancedFor(parent) || NodeUtil.isEnhancedFor(parent.getParent())) {
visitDestructuringPatternInEnhancedFor(arrayPattern);
return;
} else if (parent.isCatch()) {
visitDestructuringPatternInCatch(arrayPattern);
return;
} else {
throw new IllegalStateException("Unexpected ARRAY_PATTERN parent: " + parent);
}
}

// Convert 'var [x, y] = rhs' to:
// var temp = $jscomp.makeIterator(rhs);
// var x = temp.next().value;
// var y = temp.next().value;
/**
* Convert 'var [x, y] = rhs' to: var temp = $jscomp.makeIterator(rhs); var x = temp.next().value;
* var y = temp.next().value;
*/
private void replaceArrayPattern(
NodeTraversal t, Node arrayPattern, Node rhs, Node parent, Node nodeToDetach) {
String tempVarName = DESTRUCTURING_TEMP_VAR + (destructuringVarCounter++);
Node tempDecl = IR.var(
IR.name(tempVarName),
Expand All @@ -361,7 +379,8 @@ private void visitArrayPattern(NodeTraversal t, Node arrayPattern, Node parent)
continue;
}

Node newLHS, newRHS;
Node newLHS;
Node newRHS;
if (child.isDefaultValue()) {
// [x = defaultValue] = rhs;
// becomes
Expand Down Expand Up @@ -423,6 +442,32 @@ private void visitArrayPattern(NodeTraversal t, Node arrayPattern, Node parent)
t.reportCodeChange();
}

/**
* Convert the assignment '[x, y] = rhs' (used as an expression and not an expr result) to: (() =>
* { var temp = $jscomp.makeIterator(rhs); var x = temp.next().value; var y = temp.next().value;
* return temp; })
*/
private void wrapAssignmentInCallToArrow(NodeTraversal t, Node assignment) {
String tempVarName = DESTRUCTURING_TEMP_VAR + (destructuringVarCounter++);
Node rhs = assignment.getLastChild().detach();
Node newAssignment = IR.let(IR.name(tempVarName), rhs);
Node replacementExpr = IR.assign(assignment.getFirstChild().detach(), IR.name(tempVarName));
Node exprResult = IR.exprResult(replacementExpr);
Node returnNode = IR.returnNode(IR.name(tempVarName));
Node block = IR.block(newAssignment, exprResult, returnNode);
Node call = IR.call(IR.arrowFunction(IR.name(""), IR.paramList(), block));
call.useSourceInfoIfMissingFromForTree(assignment);
call.putBooleanProp(Node.FREE_CALL, true);
assignment.getParent().replaceChild(assignment, call);
NodeUtil.markNewScopesChanged(call, compiler);
replaceArrayPattern(
t,
replacementExpr.getFirstChild(),
replacementExpr.getLastChild(),
replacementExpr,
exprResult);
}

private void visitDestructuringPatternInEnhancedFor(Node pattern) {
Preconditions.checkArgument(pattern.isDestructuringPattern());
String tempVarName = DESTRUCTURING_TEMP_VAR + (destructuringVarCounter++);
Expand Down
2 changes: 1 addition & 1 deletion src/com/google/javascript/jscomp/TranspilationPasses.java
View file
Expand Up @@ -44,10 +44,10 @@ public static void addEs2017Passes(List<PassFactory> passes) {
public static void addEs6EarlyPasses(List<PassFactory> passes) {
passes.add(es6SuperCheck);
passes.add(es6ConvertSuper);
passes.add(es6RewriteArrowFunction);
passes.add(es6RenameVariablesInParamLists);
passes.add(es6SplitVariableDeclarations);
passes.add(es6RewriteDestructuring);
passes.add(es6RewriteArrowFunction);
}

/**
Expand Down
133 changes: 133 additions & 0 deletions test/com/google/javascript/jscomp/Es6RewriteDestructuringTest.java
View file
Expand Up @@ -638,6 +638,139 @@ public void testTypeCheck_inlineAnnotations() {
TYPE_MISMATCH_WARNING);
}

public void testDestructuringNotInExprResult() {
test(
LINE_JOINER.join("var x, a, b;", "x = ([a,b] = [1,2])"),
LINE_JOINER.join(
"var x,a,b;",
"x = (()=>{",
" let $jscomp$destructuring$var0 = [1,2];",
" var $jscomp$destructuring$var1 = $jscomp.makeIterator($jscomp$destructuring$var0);",
" a = $jscomp$destructuring$var1.next().value;",
" b = $jscomp$destructuring$var1.next().value;",
" return $jscomp$destructuring$var0;",
"})();"));

test(
LINE_JOINER.join(
"var foo = function () {", "var x, a, b;", "x = ([a,b] = [1,2]);", "}", "foo();"),
LINE_JOINER.join(
"var foo = function () {",
" var x, a, b;",
" x = (()=>{",
" let $jscomp$destructuring$var0 = [1,2];",
" var $jscomp$destructuring$var1 = $jscomp.makeIterator($jscomp$destructuring$var0);",
" a = $jscomp$destructuring$var1.next().value;",
" b = $jscomp$destructuring$var1.next().value;",
" return $jscomp$destructuring$var0;",
" })();",
"}",
"foo();"));

test(
LINE_JOINER.join("var prefix;", "for (;;[, prefix] = /\\.?([^.]+)$/.exec(prefix)){", "}"),
LINE_JOINER.join(
"var prefix;",
"for (;;(() => {",
" let $jscomp$destructuring$var0 = /\\.?([^.]+)$/.exec(prefix)",
" var $jscomp$destructuring$var1 = ",
"$jscomp.makeIterator($jscomp$destructuring$var0);",
" $jscomp$destructuring$var1.next();",
" prefix = $jscomp$destructuring$var1.next().value;",
" return $jscomp$destructuring$var0;",
" })()){",
"}"));

test(
LINE_JOINER.join(
"var prefix;",
"for (;;[, prefix] = /\\.?([^.]+)$/.exec(prefix)){",
" console.log(prefix);",
"}"),
LINE_JOINER.join(
"var prefix;",
"for (;;(() => {",
" let $jscomp$destructuring$var0 = /\\.?([^.]+)$/.exec(prefix)",
" var $jscomp$destructuring$var1 = ",
"$jscomp.makeIterator($jscomp$destructuring$var0);",
" $jscomp$destructuring$var1.next();",
" prefix = $jscomp$destructuring$var1.next().value;",
" return $jscomp$destructuring$var0;",
" })()){",
" console.log(prefix);",
"}"));

test(
LINE_JOINER.join("for (var x = 1; x < 3; [x,] = [3,4]){", " console.log(x);", "}"),
LINE_JOINER.join(
"for (var x = 1; x < 3; (()=>{",
" let $jscomp$destructuring$var0 = [3,4]",
" var $jscomp$destructuring$var1 = $jscomp.makeIterator($jscomp$destructuring$var0);",
" x = $jscomp$destructuring$var1.next().value;",
" return $jscomp$destructuring$var0;",
" })()){",
"console.log(x);",
"}"));
}

public void testNestedDestructuring() {
test(
"var [[x]] = [[1]];",
LINE_JOINER.join(
"var $jscomp$destructuring$var0 = $jscomp.makeIterator([[1]]);",
"var $jscomp$destructuring$var1 = ",
"$jscomp.makeIterator($jscomp$destructuring$var0.next().value);",
"var x = $jscomp$destructuring$var1.next().value;"));

test(
"var [[x,y],[z]] = [[1,2],[3]];",
LINE_JOINER.join(
"var $jscomp$destructuring$var0 = $jscomp.makeIterator([[1,2],[3]]);",
"var $jscomp$destructuring$var1 = ",
"$jscomp.makeIterator($jscomp$destructuring$var0.next().value);",
"var x = $jscomp$destructuring$var1.next().value;",
"var y = $jscomp$destructuring$var1.next().value;",
"var $jscomp$destructuring$var2 = ",
"$jscomp.makeIterator($jscomp$destructuring$var0.next().value);",
"var z = $jscomp$destructuring$var2.next().value;"));

test(
"var [[x,y],z] = [[1,2],3];",
LINE_JOINER.join(
"var $jscomp$destructuring$var0 = $jscomp.makeIterator([[1,2],3]);",
"var $jscomp$destructuring$var1 = ",
"$jscomp.makeIterator($jscomp$destructuring$var0.next().value);",
"var x = $jscomp$destructuring$var1.next().value;",
"var y = $jscomp$destructuring$var1.next().value;",
"var z = $jscomp$destructuring$var0.next().value;"));
}

public void testTryCatch() {
test(
LINE_JOINER.join("var x = 1;", "try {", " throw [];", "} catch ([x]) {}"),
LINE_JOINER.join(
"var x = 1;",
"try {",
" throw [];",
"} catch ($jscomp$destructuring$var0) {",
" var $jscomp$destructuring$var1 = $jscomp.makeIterator($jscomp$destructuring$var0);",
" let x = $jscomp$destructuring$var1.next().value;",
"}"));

test(
LINE_JOINER.join("var x = 1;", "try {", " throw [[]];", "} catch ([[x]]) {}"),
LINE_JOINER.join(
"var x = 1;",
"try {",
" throw [[]];",
"} catch ($jscomp$destructuring$var0) {",
" var $jscomp$destructuring$var1 = $jscomp.makeIterator($jscomp$destructuring$var0);",
" var $jscomp$destructuring$var2 = ",
"$jscomp.makeIterator($jscomp$destructuring$var1.next().value);",
" let x = $jscomp$destructuring$var2.next().value;",
"}"));
}

@Override
protected Compiler createCompiler() {
return new NoninjectingCompiler();
Expand Down

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