Tests for new lastIndex semantics (#760)

* Tests for new lastIndex semantics

Add and update tests for the lastIndex semantic change introduced in
https://github.com/tc39/ecma262/pull/627.

* Address comments

test/built-ins/RegExp/prototype/Symbol.match/builtin-coerce-lastindex.js

@@ -17,7 +17,7 @@ info: >
     21.2.5.2.2 Runtime Semantics: RegExpBuiltinExec ( R, S )
 
     [...]
-    4. Let lastIndex be ToLength(Get(R,"lastIndex")).
+    8. Else, let lastIndex be ? ToLength(? Get(R, "lastIndex")).
 features: [Symbol.match]
 ---*/
 

test/built-ins/RegExp/prototype/Symbol.match/builtin-failure-g-set-lastindex-err.js

@@ -21,18 +21,17 @@ info: >
 
     [...]
     3. Let length be the number of code units in S.
-    4. Let lastIndex be ToLength(Get(R,"lastIndex")).
     [...]
-    14. Let matchSucceeded be false.
-    15. Repeat, while matchSucceeded is false
+    11. Let matchSucceeded be false.
+    12. Repeat, while matchSucceeded is false
         a. If lastIndex > length, then
-           i. Let setStatus be Set(R, "lastIndex", 0, true).
-           ii. ReturnIfAbrupt(setStatus).
-           iii. Return null.
+           i. If global is true or sticky is true, then
+              1. Perform ? Set(R, "lastIndex", 0, true).
+           ii. Return null.
 features: [Symbol.match]
 ---*/
 
-var r = /a/;
+var r = /a/g;
 Object.defineProperty(r, 'lastIndex', { writable: false });
 
 assert.throws(TypeError, function() {

test/built-ins/RegExp/prototype/Symbol.match/builtin-failure-g-set-lastindex.js

@@ -20,18 +20,17 @@ info: >
 
     [...]
     3. Let length be the number of code units in S.
-    4. Let lastIndex be ToLength(Get(R,"lastIndex")).
     [...]
-    14. Let matchSucceeded be false.
-    15. Repeat, while matchSucceeded is false
+    11. Let matchSucceeded be false.
+    12. Repeat, while matchSucceeded is false
         a. If lastIndex > length, then
-           i. Let setStatus be Set(R, "lastIndex", 0, true).
-           ii. ReturnIfAbrupt(setStatus).
-           iii. Return null.
+           i. If global is true or sticky is true, then
+              1. Perform ? Set(R, "lastIndex", 0, true).
+           ii. Return null.
 features: [Symbol.match]
 ---*/
 
-var r = /a/;
+var r = /a/g;
 r.lastIndex = 3;
 
 r[Symbol.match]('b');

test/built-ins/RegExp/prototype/Symbol.match/builtin-y-coerce-lastindex-err.js

@@ -17,12 +17,12 @@ info: >
     21.2.5.2.2 Runtime Semantics: RegExpBuiltinExec ( R, S )
 
     [...]
-    4. Let lastIndex be ToLength(Get(R,"lastIndex")).
-    5. ReturnIfAbrupt(lastIndex).
+    7. If global is false and sticky is false, let lastIndex be 0.
+    8. Else, let lastIndex be ? ToLength(? Get(R, "lastIndex")).
 features: [Symbol.match]
 ---*/
 
-var r = /./;
+var r = /./y;
 r.lastIndex = {
   valueOf: function() {
     throw new Test262Error();

test/built-ins/RegExp/prototype/Symbol.search/lastindex-no-restore.js

@@ -0,0 +1,65 @@
+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+es6id: 21.2.5.9
+description: Behavior when some lastIndex writes should be skipped.
+info: >
+    [...]
+    4. Let previousLastIndex be ? Get(rx, "lastIndex").
+    5. If SameValue(previousLastIndex, 0) is false, then
+       a. Perform ? Set(rx, "lastIndex", 0, true).
+    [...]
+    7. Let currentLastIndex be ? Get(rx, "lastIndex").
+    8. If SameValue(currentLastIndex, previousLastIndex) is false, then
+       a. Perform ? Set(rx, "lastIndex", previousLastIndex, true).
+    [...]
+features: [Symbol.search]
+---*/
+
+var lastIndexValue;
+var lastIndexValueAfterExec;
+var lastIndexReads;
+var lastIndexWrites;
+var execCallCount;
+var result;
+
+var fakeRe = {
+  get lastIndex() {
+    lastIndexReads++;
+    return lastIndexValue;
+  },
+  set lastIndex(_) {
+    lastIndexWrites++;
+    lastIndexValue = _;
+  },
+  exec: function() {
+    execCallCount++;
+    lastIndexValue = lastIndexValueAfterExec;
+    return null;
+  }
+};
+
+function reset(value, valueAfterExec) {
+  lastIndexValue = value;
+  lastIndexValueAfterExec = valueAfterExec;
+  lastIndexReads = 0;
+  lastIndexWrites = 0;
+  execCallCount = 0;
+}
+
+reset(0, 0);
+result = RegExp.prototype[Symbol.search].call(fakeRe);
+assert.sameValue(result, -1);
+assert.sameValue(lastIndexValue, 0);
+assert.sameValue(lastIndexReads, 2);
+assert.sameValue(lastIndexWrites, 0);
+assert.sameValue(execCallCount, 1);
+
+reset(420, 420);
+result = RegExp.prototype[Symbol.search].call(fakeRe);
+assert.sameValue(result, -1);
+assert.sameValue(lastIndexValue, 420);
+assert.sameValue(lastIndexReads, 2);
+assert.sameValue(lastIndexWrites, 1);
+assert.sameValue(execCallCount, 1);

test/built-ins/RegExp/prototype/Symbol.search/set-lastindex-restore-err.js

@@ -8,18 +8,19 @@ description: >
     match execution
 info: >
     [...]
-    11. Let status be Set(rx, "lastIndex", previousLastIndex, true).
-    12. ReturnIfAbrupt(status).
+    8. If SameValue(currentLastIndex, previousLastIndex) is false, then
+        a. Perform ? Set(rx, "lastIndex", previousLastIndex, true).
 features: [Symbol.search]
 ---*/
 
 var callCount;
 var poisonedLastIndex = {
-  get lastIndex() {},
+  get lastIndex() { return this.lastIndex_; },
   set lastIndex(_) {
     if (callCount === 1) {
       throw new Test262Error();
     }
+    this.lastIndex_ = _;
   },
   exec: function() {
     callCount += 1;

test/built-ins/RegExp/prototype/Symbol.search/set-lastindex-restore.js

@@ -6,20 +6,23 @@ es6id: 21.2.5.9
 description: The `lastIndex` value is restored following match execution
 info: >
     [...]
-    11. Let status be Set(rx, "lastIndex", previousLastIndex, true).
+    8. If SameValue(currentLastIndex, previousLastIndex) is false, then
+       a. Perform ? Set(rx, "lastIndex", previousLastIndex, true).
     [...]
 features: [Symbol.search]
 ---*/
 
-var latestValue;
+var latestValue = 86;
+var callCount = 0;
 var fakeRe = {
   get lastIndex() {
-    return 86;
+    return latestValue;
   },
   set lastIndex(_) {
     latestValue = _;
   },
   exec: function() {
+    callCount++;
     latestValue = null;
     return null;
   }
@@ -27,4 +30,5 @@ var fakeRe = {
 
 RegExp.prototype[Symbol.search].call(fakeRe);
 
+assert.sameValue(callCount, 1);
 assert.sameValue(latestValue, 86);

test/built-ins/RegExp/prototype/exec/failure-g-lastindex-reset.js

@@ -0,0 +1,52 @@
+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: lastIndex is read and reset to 0 when global is set and the match
+             fails.
+es6id: 21.2.5.2.2
+info: >
+    21.2.5.2.2 Runtime Semantics: RegExpBuiltinExec ( R, S )
+
+    [...]
+    4. Let flags be R.[[OriginalFlags]].
+    5. If flags contains "g", let global be true, else let global be false.
+    [...]
+    7. If global is false and sticky is false, let lastIndex be 0.
+    8. Else, let lastIndex be ? ToLength(? Get(R, "lastIndex")).
+    [...]
+    12. Repeat, while matchSucceeded is false
+        [...]
+        c. If r is failure, then
+           i. If sticky is true, then
+              1. Perform ? Set(R, "lastIndex", 0, true).
+              2. Return null.
+           ii. Let lastIndex be AdvanceStringIndex(S, lastIndex, fullUnicode).
+---*/
+
+var lastIndexReads;
+var result;
+
+var r = /a/g;
+
+function reset(value) {
+  r.lastIndex = {
+    valueOf: function() {
+      lastIndexReads++;
+      return value;
+    }
+  };
+  lastIndexReads = 0;
+}
+
+reset(42);  // lastIndex beyond end of string.
+result = r.exec('abc');
+assert.sameValue(result, null);
+assert.sameValue(r.lastIndex, 0);
+assert.sameValue(lastIndexReads, 1);
+
+reset(-1);  // No match.
+result = r.exec('nbc');
+assert.sameValue(result, null);
+assert.sameValue(r.lastIndex, 0);
+assert.sameValue(lastIndexReads, 1);

test/built-ins/RegExp/prototype/exec/failure-lastindex-no-access.js

@@ -0,0 +1,33 @@
+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: lastIndex is not accessed when global and sticky are unset.
+es6id: 21.2.5.2.2
+info: >
+    21.2.5.2.2 Runtime Semantics: RegExpBuiltinExec ( R, S )
+
+    [...]
+    7. If global is false and sticky is false, let lastIndex be 0.
+    [...]
+    12. Repeat, while matchSucceeded is false
+        [...]
+        c. If r is failure, then
+           i. If sticky is true, then
+              1. Perform ? Set(R, "lastIndex", 0, true).
+              2. Return null.
+---*/
+
+var thrower = {
+  valueOf: function() {
+    throw new Test262Error();
+  }
+};
+
+var r = /a/;
+r.lastIndex = thrower;
+
+var result = r.exec('nbc');
+assert.sameValue(result, null);
+assert.sameValue(r.lastIndex, thrower);
+

test/built-ins/RegExp/prototype/exec/success-g-lastindex-no-access.js

@@ -0,0 +1,33 @@
+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: lastIndex is accessed when global is set.
+es6id: 21.2.5.2.2
+info: >
+    21.2.5.2.2 Runtime Semantics: RegExpBuiltinExec ( R, S )
+
+    [...]
+    4. Let flags be R.[[OriginalFlags]].
+    5. If flags contains "g", let global be true, else let global be false.
+    [...]
+    15. If global is true or sticky is true, then
+        a. Perform ? Set(R, "lastIndex", e, true).
+---*/
+
+var lastIndexReads = 0;
+
+var r = /./g;
+r.lastIndex = {
+  valueOf: function() {
+    lastIndexReads++;
+    return 0;
+  }
+};
+
+var result = r.exec('abc');
+assert.sameValue(result.length, 1);
+assert.sameValue(result[0], 'a');
+assert.sameValue(r.lastIndex, 1);
+assert.sameValue(lastIndexReads, 1);
+

test/built-ins/RegExp/prototype/exec/success-lastindex-no-access.js

@@ -0,0 +1,33 @@
+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: lastIndex is not accessed when global and sticky are unset.
+es6id: 21.2.5.2.2
+info: >
+    21.2.5.2.2 Runtime Semantics: RegExpBuiltinExec ( R, S )
+
+    [...]
+    4. Let flags be R.[[OriginalFlags]].
+    5. If flags contains "g", let global be true, else let global be false.
+    [...]
+    15. If global is true or sticky is true, then
+        a. Perform ? Set(R, "lastIndex", e, true).
+---*/
+
+var thrower = {
+  valueOf: function() {
+    throw new Test262Error();
+  }
+};
+
+var r = /./;
+r.lastIndex = thrower;
+
+var result = r.exec('abc');
+
+assert.notSameValue(result, null);
+assert.sameValue(result.length, 1);
+assert.sameValue(result[0], 'a');
+assert.sameValue(r.lastIndex, thrower);
+