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EatingWTyler Breisacher
EatingW
authored and
Tyler Breisacher
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In ES6RewriteDestructuring visitArrayPattern, if the parent of the destructuring 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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5 files changed

+399
-17
lines changed

5 files changed

+399
-17
lines changed

‎src/com/google/javascript/jscomp/Es6RewriteDestructuring.java

+61-16
Original file line numberDiff line numberDiff line change
@@ -53,6 +53,9 @@ public void hotSwapScript(Node scriptRoot, Node originalRoot) {
5353
@Override
5454
public boolean shouldTraverse(NodeTraversal t, Node n, Node parent) {
5555
switch (n.getToken()) {
56+
case FUNCTION:
57+
visitFunction(t, n);
58+
break;
5659
case PARAM_LIST:
5760
visitParamList(t, n, parent);
5861
break;
@@ -82,6 +85,19 @@ public void visit(NodeTraversal t, Node n, Node parent) {
8285
}
8386
}
8487

88+
/**
89+
* If the function is an arrow function, wrap the body in a block if it is not already a block.
90+
*/
91+
private void visitFunction(NodeTraversal t, Node function) {
92+
Node body = function.getLastChild();
93+
if (!body.isNormalBlock()) {
94+
body.detach();
95+
Node replacement = IR.block(IR.returnNode(body)).useSourceInfoIfMissingFromForTree(body);
96+
function.addChildToBack(replacement);
97+
t.reportCodeChange();
98+
}
99+
}
100+
85101
/**
86102
* Processes trailing default and rest parameters.
87103
*/
@@ -203,7 +219,8 @@ private void visitForOf(Node node) {
203219
}
204220

205221
private void visitObjectPattern(NodeTraversal t, Node objectPattern, Node parent) {
206-
Node rhs, nodeToDetach;
222+
Node rhs;
223+
Node nodeToDetach;
207224
if (NodeUtil.isNameDeclaration(parent) && !NodeUtil.isEnhancedFor(parent.getParent())) {
208225
rhs = objectPattern.getNext();
209226
nodeToDetach = parent;
@@ -244,7 +261,8 @@ private void visitObjectPattern(NodeTraversal t, Node objectPattern, Node parent
244261
for (Node child = objectPattern.getFirstChild(), next; child != null; child = next) {
245262
next = child.getNext();
246263

247-
Node newLHS, newRHS;
264+
Node newLHS;
265+
Node newRHS;
248266
if (child.isStringKey()) {
249267
if (!child.hasChildren()) { // converting shorthand
250268
Node name = IR.name(child.getString());
@@ -314,35 +332,35 @@ private void visitObjectPattern(NodeTraversal t, Node objectPattern, Node parent
314332
}
315333

316334
private void visitArrayPattern(NodeTraversal t, Node arrayPattern, Node parent) {
317-
Node rhs, nodeToDetach;
318335
if (NodeUtil.isNameDeclaration(parent) && !NodeUtil.isEnhancedFor(parent.getParent())) {
319-
rhs = arrayPattern.getNext();
320-
nodeToDetach = parent;
336+
replaceArrayPattern(t, arrayPattern, arrayPattern.getNext(), parent, parent);
321337
} else if (parent.isAssign()) {
322-
rhs = arrayPattern.getNext();
323-
nodeToDetach = parent.getParent();
324-
Preconditions.checkState(nodeToDetach.isExprResult());
338+
if (parent.getParent().isExprResult()) {
339+
replaceArrayPattern(t, arrayPattern, arrayPattern.getNext(), parent, parent.getParent());
340+
} else {
341+
wrapAssignmentInCallToArrow(t, parent);
342+
}
325343
} else if (parent.isArrayPattern()
326344
|| parent.isRest()
327345
|| parent.isDefaultValue()
328346
|| parent.isStringKey()) {
329347
// This is a nested array pattern. Don't do anything now; we'll visit it
330348
// after visiting the parent.
331-
return;
332349
} else if (NodeUtil.isEnhancedFor(parent) || NodeUtil.isEnhancedFor(parent.getParent())) {
333350
visitDestructuringPatternInEnhancedFor(arrayPattern);
334-
return;
335351
} else if (parent.isCatch()) {
336352
visitDestructuringPatternInCatch(arrayPattern);
337-
return;
338353
} else {
339354
throw new IllegalStateException("Unexpected ARRAY_PATTERN parent: " + parent);
340355
}
356+
}
341357

342-
// Convert 'var [x, y] = rhs' to:
343-
// var temp = $jscomp.makeIterator(rhs);
344-
// var x = temp.next().value;
345-
// var y = temp.next().value;
358+
/**
359+
* Convert 'var [x, y] = rhs' to: var temp = $jscomp.makeIterator(rhs); var x = temp.next().value;
360+
* var y = temp.next().value;
361+
*/
362+
private void replaceArrayPattern(
363+
NodeTraversal t, Node arrayPattern, Node rhs, Node parent, Node nodeToDetach) {
346364
String tempVarName = DESTRUCTURING_TEMP_VAR + (destructuringVarCounter++);
347365
Node tempDecl = IR.var(
348366
IR.name(tempVarName),
@@ -361,7 +379,8 @@ private void visitArrayPattern(NodeTraversal t, Node arrayPattern, Node parent)
361379
continue;
362380
}
363381

364-
Node newLHS, newRHS;
382+
Node newLHS;
383+
Node newRHS;
365384
if (child.isDefaultValue()) {
366385
// [x = defaultValue] = rhs;
367386
// becomes
@@ -423,6 +442,32 @@ private void visitArrayPattern(NodeTraversal t, Node arrayPattern, Node parent)
423442
t.reportCodeChange();
424443
}
425444

445+
/**
446+
* Convert the assignment '[x, y] = rhs' (used as an expression and not an expr result) to: (() =>
447+
* { var temp = $jscomp.makeIterator(rhs); var x = temp.next().value; var y = temp.next().value;
448+
* return temp; })
449+
*/
450+
private void wrapAssignmentInCallToArrow(NodeTraversal t, Node assignment) {
451+
String tempVarName = DESTRUCTURING_TEMP_VAR + (destructuringVarCounter++);
452+
Node rhs = assignment.getLastChild().detach();
453+
Node newAssignment = IR.let(IR.name(tempVarName), rhs);
454+
Node replacementExpr = IR.assign(assignment.getFirstChild().detach(), IR.name(tempVarName));
455+
Node exprResult = IR.exprResult(replacementExpr);
456+
Node returnNode = IR.returnNode(IR.name(tempVarName));
457+
Node block = IR.block(newAssignment, exprResult, returnNode);
458+
Node call = IR.call(IR.arrowFunction(IR.name(""), IR.paramList(), block));
459+
call.useSourceInfoIfMissingFromForTree(assignment);
460+
call.putBooleanProp(Node.FREE_CALL, true);
461+
assignment.getParent().replaceChild(assignment, call);
462+
NodeUtil.markNewScopesChanged(call, compiler);
463+
replaceArrayPattern(
464+
t,
465+
replacementExpr.getFirstChild(),
466+
replacementExpr.getLastChild(),
467+
replacementExpr,
468+
exprResult);
469+
}
470+
426471
private void visitDestructuringPatternInEnhancedFor(Node pattern) {
427472
Preconditions.checkArgument(pattern.isDestructuringPattern());
428473
String tempVarName = DESTRUCTURING_TEMP_VAR + (destructuringVarCounter++);

‎src/com/google/javascript/jscomp/TranspilationPasses.java

+1-1
Original file line numberDiff line numberDiff line change
@@ -44,10 +44,10 @@ public static void addEs2017Passes(List<PassFactory> passes) {
4444
public static void addEs6EarlyPasses(List<PassFactory> passes) {
4545
passes.add(es6SuperCheck);
4646
passes.add(es6ConvertSuper);
47-
passes.add(es6RewriteArrowFunction);
4847
passes.add(es6RenameVariablesInParamLists);
4948
passes.add(es6SplitVariableDeclarations);
5049
passes.add(es6RewriteDestructuring);
50+
passes.add(es6RewriteArrowFunction);
5151
}
5252

5353
/**

‎test/com/google/javascript/jscomp/Es6RewriteDestructuringTest.java

+133
Original file line numberDiff line numberDiff line change
@@ -638,6 +638,139 @@ public void testTypeCheck_inlineAnnotations() {
638638
TYPE_MISMATCH_WARNING);
639639
}
640640

641+
public void testDestructuringNotInExprResult() {
642+
test(
643+
LINE_JOINER.join("var x, a, b;", "x = ([a,b] = [1,2])"),
644+
LINE_JOINER.join(
645+
"var x,a,b;",
646+
"x = (()=>{",
647+
" let $jscomp$destructuring$var0 = [1,2];",
648+
" var $jscomp$destructuring$var1 = $jscomp.makeIterator($jscomp$destructuring$var0);",
649+
" a = $jscomp$destructuring$var1.next().value;",
650+
" b = $jscomp$destructuring$var1.next().value;",
651+
" return $jscomp$destructuring$var0;",
652+
"})();"));
653+
654+
test(
655+
LINE_JOINER.join(
656+
"var foo = function () {", "var x, a, b;", "x = ([a,b] = [1,2]);", "}", "foo();"),
657+
LINE_JOINER.join(
658+
"var foo = function () {",
659+
" var x, a, b;",
660+
" x = (()=>{",
661+
" let $jscomp$destructuring$var0 = [1,2];",
662+
" var $jscomp$destructuring$var1 = $jscomp.makeIterator($jscomp$destructuring$var0);",
663+
" a = $jscomp$destructuring$var1.next().value;",
664+
" b = $jscomp$destructuring$var1.next().value;",
665+
" return $jscomp$destructuring$var0;",
666+
" })();",
667+
"}",
668+
"foo();"));
669+
670+
test(
671+
LINE_JOINER.join("var prefix;", "for (;;[, prefix] = /\\.?([^.]+)$/.exec(prefix)){", "}"),
672+
LINE_JOINER.join(
673+
"var prefix;",
674+
"for (;;(() => {",
675+
" let $jscomp$destructuring$var0 = /\\.?([^.]+)$/.exec(prefix)",
676+
" var $jscomp$destructuring$var1 = ",
677+
"$jscomp.makeIterator($jscomp$destructuring$var0);",
678+
" $jscomp$destructuring$var1.next();",
679+
" prefix = $jscomp$destructuring$var1.next().value;",
680+
" return $jscomp$destructuring$var0;",
681+
" })()){",
682+
"}"));
683+
684+
test(
685+
LINE_JOINER.join(
686+
"var prefix;",
687+
"for (;;[, prefix] = /\\.?([^.]+)$/.exec(prefix)){",
688+
" console.log(prefix);",
689+
"}"),
690+
LINE_JOINER.join(
691+
"var prefix;",
692+
"for (;;(() => {",
693+
" let $jscomp$destructuring$var0 = /\\.?([^.]+)$/.exec(prefix)",
694+
" var $jscomp$destructuring$var1 = ",
695+
"$jscomp.makeIterator($jscomp$destructuring$var0);",
696+
" $jscomp$destructuring$var1.next();",
697+
" prefix = $jscomp$destructuring$var1.next().value;",
698+
" return $jscomp$destructuring$var0;",
699+
" })()){",
700+
" console.log(prefix);",
701+
"}"));
702+
703+
test(
704+
LINE_JOINER.join("for (var x = 1; x < 3; [x,] = [3,4]){", " console.log(x);", "}"),
705+
LINE_JOINER.join(
706+
"for (var x = 1; x < 3; (()=>{",
707+
" let $jscomp$destructuring$var0 = [3,4]",
708+
" var $jscomp$destructuring$var1 = $jscomp.makeIterator($jscomp$destructuring$var0);",
709+
" x = $jscomp$destructuring$var1.next().value;",
710+
" return $jscomp$destructuring$var0;",
711+
" })()){",
712+
"console.log(x);",
713+
"}"));
714+
}
715+
716+
public void testNestedDestructuring() {
717+
test(
718+
"var [[x]] = [[1]];",
719+
LINE_JOINER.join(
720+
"var $jscomp$destructuring$var0 = $jscomp.makeIterator([[1]]);",
721+
"var $jscomp$destructuring$var1 = ",
722+
"$jscomp.makeIterator($jscomp$destructuring$var0.next().value);",
723+
"var x = $jscomp$destructuring$var1.next().value;"));
724+
725+
test(
726+
"var [[x,y],[z]] = [[1,2],[3]];",
727+
LINE_JOINER.join(
728+
"var $jscomp$destructuring$var0 = $jscomp.makeIterator([[1,2],[3]]);",
729+
"var $jscomp$destructuring$var1 = ",
730+
"$jscomp.makeIterator($jscomp$destructuring$var0.next().value);",
731+
"var x = $jscomp$destructuring$var1.next().value;",
732+
"var y = $jscomp$destructuring$var1.next().value;",
733+
"var $jscomp$destructuring$var2 = ",
734+
"$jscomp.makeIterator($jscomp$destructuring$var0.next().value);",
735+
"var z = $jscomp$destructuring$var2.next().value;"));
736+
737+
test(
738+
"var [[x,y],z] = [[1,2],3];",
739+
LINE_JOINER.join(
740+
"var $jscomp$destructuring$var0 = $jscomp.makeIterator([[1,2],3]);",
741+
"var $jscomp$destructuring$var1 = ",
742+
"$jscomp.makeIterator($jscomp$destructuring$var0.next().value);",
743+
"var x = $jscomp$destructuring$var1.next().value;",
744+
"var y = $jscomp$destructuring$var1.next().value;",
745+
"var z = $jscomp$destructuring$var0.next().value;"));
746+
}
747+
748+
public void testTryCatch() {
749+
test(
750+
LINE_JOINER.join("var x = 1;", "try {", " throw [];", "} catch ([x]) {}"),
751+
LINE_JOINER.join(
752+
"var x = 1;",
753+
"try {",
754+
" throw [];",
755+
"} catch ($jscomp$destructuring$var0) {",
756+
" var $jscomp$destructuring$var1 = $jscomp.makeIterator($jscomp$destructuring$var0);",
757+
" let x = $jscomp$destructuring$var1.next().value;",
758+
"}"));
759+
760+
test(
761+
LINE_JOINER.join("var x = 1;", "try {", " throw [[]];", "} catch ([[x]]) {}"),
762+
LINE_JOINER.join(
763+
"var x = 1;",
764+
"try {",
765+
" throw [[]];",
766+
"} catch ($jscomp$destructuring$var0) {",
767+
" var $jscomp$destructuring$var1 = $jscomp.makeIterator($jscomp$destructuring$var0);",
768+
" var $jscomp$destructuring$var2 = ",
769+
"$jscomp.makeIterator($jscomp$destructuring$var1.next().value);",
770+
" let x = $jscomp$destructuring$var2.next().value;",
771+
"}"));
772+
}
773+
641774
@Override
642775
protected Compiler createCompiler() {
643776
return new NoninjectingCompiler();

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