Bug 1054630 - Collect telemetry on usage of SpiderMonkey's deprecated language extensions: for-each, destructuring for-in, legacy generators, and expression closures. r=till

browser/base/content/abouthome/aboutHome.js

@@ -2,6 +2,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+"use strict";
+
 const SEARCH_ENGINES = {
   "Google": {
     // This is the "2x" image designed for OS X retina resolution, Windows at 192dpi, etc.;
@@ -269,13 +271,13 @@ function ensureSnippetsMapThen(aCallback)
 
       // The cache has been filled up, create the snippets map.
       gSnippetsMap = Object.freeze({
-        get: function (aKey) cache.get(aKey),
+        get: (aKey) => cache.get(aKey),
         set: function (aKey, aValue) {
           db.transaction(SNIPPETS_OBJECTSTORE_NAME, "readwrite")
             .objectStore(SNIPPETS_OBJECTSTORE_NAME).put(aValue, aKey);
           return cache.set(aKey, aValue);
         },
-        has: function (aKey) cache.has(aKey),
+        has: (aKey) => cache.has(aKey),
         delete: function (aKey) {
           db.transaction(SNIPPETS_OBJECTSTORE_NAME, "readwrite")
             .objectStore(SNIPPETS_OBJECTSTORE_NAME).delete(aKey);
@@ -286,7 +288,7 @@ function ensureSnippetsMapThen(aCallback)
             .objectStore(SNIPPETS_OBJECTSTORE_NAME).clear();
           return cache.clear();
         },
-        get size() cache.size
+        get size() { return cache.size; },
       });
 
       setTimeout(invokeCallbacks, 0);

browser/base/content/browser.xul

@@ -712,7 +712,7 @@
                      ontextreverted="return this.handleRevert();"
                      pageproxystate="invalid"
                      onfocus="document.getElementById('identity-box').style.MozUserFocus= 'normal'"
-                     onblur="setTimeout(function() document.getElementById('identity-box').style.MozUserFocus = '', 0);">
+                     onblur="setTimeout(() => { document.getElementById('identity-box').style.MozUserFocus = ''; }, 0);">
               <box id="notification-popup-box" hidden="true" align="center">
                 <image id="default-notification-icon" class="notification-anchor-icon" role="button"/>
                 <image id="identity-notification-icon" class="notification-anchor-icon" role="button"/>

js/src/frontend/Parser.cpp

@@ -430,6 +430,10 @@ Parser<ParseHandler>::Parser(ExclusiveContext *cx, LifoAlloc *alloc,
     foldConstants(foldConstants),
     abortedSyntaxParse(false),
     isUnexpectedEOF_(false),
+    sawDeprecatedForEach(false),
+    sawDeprecatedDestructuringForIn(false),
+    sawDeprecatedLegacyGenerator(false),
+    sawDeprecatedExpressionClosure(false),
     handler(cx, *alloc, tokenStream, foldConstants, syntaxParser, lazyOuterFunction)
 {
     {
@@ -449,6 +453,8 @@ Parser<ParseHandler>::Parser(ExclusiveContext *cx, LifoAlloc *alloc,
 template <typename ParseHandler>
 Parser<ParseHandler>::~Parser()
 {
+    accumulateTelemetry();
+
     alloc.release(tempPoolMark);
 
     /*
@@ -2259,6 +2265,10 @@ Parser<ParseHandler>::functionArgsAndBodyGeneric(Node pn, HandleFunction fun, Fu
             report(ParseError, false, null(), JSMSG_CURLY_BEFORE_BODY);
             return false;
         }
+
+        if (kind != Arrow)
+            sawDeprecatedExpressionClosure = true;
+
         tokenStream.ungetToken();
         bodyType = ExpressionBody;
         fun->setIsExprClosure();
@@ -4083,6 +4093,7 @@ Parser<FullParseHandler>::forStatement()
     if (allowsForEachIn() && tokenStream.matchContextualKeyword(context->names().each)) {
         iflags = JSITER_FOREACH;
         isForEach = true;
+        sawDeprecatedForEach = true;
     }
 
     MUST_MATCH_TOKEN(TOK_LP, JSMSG_PAREN_AFTER_FOR);
@@ -4300,8 +4311,10 @@ Parser<FullParseHandler>::forStatement()
                  * Destructuring for-in requires [key, value] enumeration
                  * in JS1.7.
                  */
-                if (!isForEach && headKind == PNK_FORIN)
+                if (!isForEach && headKind == PNK_FORIN) {
                     iflags |= JSITER_FOREACH | JSITER_KEYVALUE;
+                    sawDeprecatedDestructuringForIn = true;
+                }
             }
             break;
 
@@ -4803,6 +4816,7 @@ Parser<ParseHandler>::yieldExpression()
         }
 
         pc->sc->asFunctionBox()->setGeneratorKind(LegacyGenerator);
+        sawDeprecatedLegacyGenerator = true;
 
         if (pc->funHasReturnExpr) {
             /* As in Python (see PEP-255), disallow return v; in generators. */
@@ -7573,6 +7587,47 @@ Parser<ParseHandler>::exprInParens()
     return pn;
 }
 
+template <typename ParseHandler>
+void
+Parser<ParseHandler>::accumulateTelemetry()
+{
+    JSContext* cx = context->maybeJSContext();
+    if (!cx)
+        return;
+    JSAccumulateTelemetryDataCallback cb = cx->runtime()->telemetryCallback;
+    if (!cb)
+        return;
+    const char* filename = getFilename();
+    if (!filename)
+        return;
+
+    bool isHTTP = strncmp(filename, "http://", 7) == 0 || strncmp(filename, "https://", 8) == 0;
+
+    // Only report telemetry for web content, not add-ons or chrome JS.
+    if (!isHTTP)
+        return;
+
+    enum DeprecatedLanguageExtensions {
+        DeprecatedForEach = 0,            // JS 1.6+
+        DeprecatedDestructuringForIn = 1, // JS 1.7 only
+        DeprecatedLegacyGenerator = 2,    // JS 1.7+
+        DeprecatedExpressionClosure = 3,  // Added in JS 1.8, but not version-gated
+    };
+
+    // Hazard analysis can't tell that the telemetry callbacks don't GC.
+    JS::AutoSuppressGCAnalysis nogc;
+
+    // Call back into Firefox's Telemetry reporter.
+    if (sawDeprecatedForEach)
+        (*cb)(JS_TELEMETRY_DEPRECATED_LANGUAGE_EXTENSIONS_IN_CONTENT, DeprecatedForEach);
+    if (sawDeprecatedDestructuringForIn)
+        (*cb)(JS_TELEMETRY_DEPRECATED_LANGUAGE_EXTENSIONS_IN_CONTENT, DeprecatedDestructuringForIn);
+    if (sawDeprecatedLegacyGenerator)
+        (*cb)(JS_TELEMETRY_DEPRECATED_LANGUAGE_EXTENSIONS_IN_CONTENT, DeprecatedLegacyGenerator);
+    if (sawDeprecatedExpressionClosure)
+        (*cb)(JS_TELEMETRY_DEPRECATED_LANGUAGE_EXTENSIONS_IN_CONTENT, DeprecatedExpressionClosure);
+}
+
 template class Parser<FullParseHandler>;
 template class Parser<SyntaxParseHandler>;
 

js/src/frontend/Parser.h

@@ -350,6 +350,12 @@ class Parser : private JS::AutoGCRooter, public StrictModeGetter
     /* Unexpected end of input, i.e. TOK_EOF not at top-level. */
     bool isUnexpectedEOF_:1;
 
+    /* Used for collecting telemetry on SpiderMonkey's deprecated language extensions. */
+    bool sawDeprecatedForEach:1;
+    bool sawDeprecatedDestructuringForIn:1;
+    bool sawDeprecatedLegacyGenerator:1;
+    bool sawDeprecatedExpressionClosure:1;
+
     typedef typename ParseHandler::Node Node;
     typedef typename ParseHandler::DefinitionNode DefinitionNode;
 
@@ -658,6 +664,8 @@ class Parser : private JS::AutoGCRooter, public StrictModeGetter
 
     bool asmJS(Node list);
 
+    void accumulateTelemetry();
+
     friend class LegacyCompExprTransplanter;
     friend struct BindData<ParseHandler>;
 };

js/src/jsfriendapi.h

@@ -119,7 +119,8 @@ enum {
     JS_TELEMETRY_GC_INCREMENTAL_DISABLED,
     JS_TELEMETRY_GC_NON_INCREMENTAL,
     JS_TELEMETRY_GC_SCC_SWEEP_TOTAL_MS,
-    JS_TELEMETRY_GC_SCC_SWEEP_MAX_PAUSE_MS
+    JS_TELEMETRY_GC_SCC_SWEEP_MAX_PAUSE_MS,
+    JS_TELEMETRY_DEPRECATED_LANGUAGE_EXTENSIONS_IN_CONTENT
 };
 
 typedef void

js/xpconnect/src/XPCJSRuntime.cpp

@@ -2929,6 +2929,12 @@ AccumulateTelemetryCallback(int id, uint32_t sample)
       case JS_TELEMETRY_GC_SCC_SWEEP_MAX_PAUSE_MS:
         Telemetry::Accumulate(Telemetry::GC_SCC_SWEEP_MAX_PAUSE_MS, sample);
         break;
+      case JS_TELEMETRY_DEPRECATED_LANGUAGE_EXTENSIONS_IN_CONTENT:
+        MOZ_ASSERT(sample <= 3);
+        Telemetry::Accumulate(Telemetry::JS_DEPRECATED_LANGUAGE_EXTENSIONS_IN_CONTENT, sample);
+        break;
+      default:
+        MOZ_ASSERT_UNREACHABLE("Unexpected JS_TELEMETRY id");
     }
 }
 

toolkit/components/telemetry/Histograms.json

@@ -318,6 +318,12 @@
     "kind": "flag",
     "description": "Has seen location error"
   },
+  "JS_DEPRECATED_LANGUAGE_EXTENSIONS_IN_CONTENT": {
+    "expires_in_version": "never",
+    "kind": "enumerated",
+    "n_values": 10,
+    "description": "Use of SpiderMonkey's deprecated language extensions in web content: ForEach, DestructuringForIn, LegacyGenerator, ExpressionClosure"
+  },
   "TELEMETRY_PING": {
     "expires_in_version": "never",
     "kind": "exponential",