Bug 1300336 - Allow pseudo-arrays to have a length property. r=fitzgen

devtools/client/webconsole/test/browser_webconsole_output_06.js

@@ -111,7 +111,7 @@ var inputTests = [
     input: '["' + testStrIn + '", "' + testStrIn + '", "' + testStrIn + '"]',
     output: 'Array [ "' + testStrOut + '", "' + testStrOut + '", "' +
             testStrOut + '" ]',
-    inspectable: false,
+    inspectable: true,
     printOutput: "SHOW\nALL\nOF\nTHIS\nON\nA\nSINGLE\nLINE ONLY. ESCAPE " +
                  "ALL NEWLINE,SHOW\nALL\nOF\nTHIS\nON\nA\nSINGLE\nLINE ONLY. " +
                  "ESCAPE ALL NEWLINE,SHOW\nALL\nOF\nTHIS\nON\nA\nSINGLE\n" +
@@ -124,7 +124,8 @@ var inputTests = [
     input: '({0: "a", 1: "b"})',
     output: 'Object [ "a", "b" ]',
     printOutput: "[object Object]",
-    inspectable: false,
+    inspectable: true,
+    variablesViewLabel: "Object[2]",
   },
 
   // 14
@@ -132,7 +133,8 @@ var inputTests = [
     input: '({0: "a", 42: "b"})',
     output: 'Object { 0: "a", 42: "b" }',
     printOutput: "[object Object]",
-    inspectable: false,
+    inspectable: true,
+    variablesViewLabel: "Object",
   },
 
   // 15
@@ -165,6 +167,96 @@ var inputTests = [
     inspectable: true,
     variablesViewLabel: "Object",
   },
+
+  // 18
+  {
+    input: '({})',
+    output: 'Object {  }',
+    printOutput: "[object Object]",
+    inspectable: true,
+    variablesViewLabel: "Object",
+  },
+
+  // 19
+  {
+    input: '({length: 0})',
+    output: 'Object [  ]',
+    printOutput: "[object Object]",
+    inspectable: true,
+    variablesViewLabel: "Object[0]",
+  },
+
+  // 20
+  {
+    input: '({length: 1})',
+    output: 'Object { length: 1 }',
+    printOutput: "[object Object]",
+    inspectable: true,
+    variablesViewLabel: "Object",
+  },
+
+  // 21
+  {
+    input: '({0: "a", 1: "b", length: 1})',
+    output: 'Object { 1: "b", length: 1, 1 more\u2026 }',
+    printOutput: "[object Object]",
+    inspectable: true,
+    variablesViewLabel: "Object",
+  },
+
+  // 22
+  {
+    input: '({0: "a", 1: "b", length: 2})',
+    output: 'Object [ "a", "b" ]',
+    printOutput: "[object Object]",
+    inspectable: true,
+    variablesViewLabel: "Object[2]",
+  },
+
+  // 23
+  {
+    input: '({0: "a", 1: "b", length: 3})',
+    output: 'Object { length: 3, 2 more\u2026 }',
+    printOutput: "[object Object]",
+    inspectable: true,
+    variablesViewLabel: "Object",
+  },
+
+  // 24
+  {
+    input: '({0: "a", 2: "b", length: 2})',
+    output: 'Object { 2: "b", length: 2, 1 more\u2026 }',
+    printOutput: "[object Object]",
+    inspectable: true,
+    variablesViewLabel: "Object",
+  },
+
+  // 25
+  {
+    input: '({0: "a", 2: "b", length: 3})',
+    output: 'Object { length: 3, 2 more\u2026 }',
+    printOutput: "[object Object]",
+    inspectable: true,
+    variablesViewLabel: "Object",
+  },
+
+  // 26
+  {
+    input: '({0: "a", b: "b", length: 1})',
+    output: 'Object { b: "b", length: 1, 1 more\u2026 }',
+    printOutput: "[object Object]",
+    inspectable: true,
+    variablesViewLabel: "Object",
+  },
+
+  // 27
+  {
+    input: '({0: "a", b: "b", length: 2})',
+    output: 'Object { b: "b", length: 2, 1 more\u2026 }',
+    printOutput: "[object Object]",
+    inspectable: true,
+    variablesViewLabel: "Object",
+  },
 ];
 
 function test() {

devtools/server/actors/object.js

@@ -1800,13 +1800,27 @@ DebuggerServer.ObjectActorPreviewers.Object = [
       return false;
     }
 
-    // Making sure that all keys are array indices, that is:
-    // `ToString(ToUint32(key)) === key  &&  key !== "4294967295"`.
-    // Also ensuring that the keys are consecutive and start at "0",
-    // this implies checking `key !== "4294967295"` is not necessary.
+    // Pseudo-arrays should only have array indices and, optionally, a "length" property.
+    // Since array indices are sorted first, check if the last property is "length".
+    if(keys[keys.length-1] === "length") {
+      keys.pop();
+      // The value of "length" should equal the number of other properties. If eventually
+      // we allow sparse pseudo-arrays, we should check whether it's a Uint32 instead.
+      if(rawObj.length !== keys.length) {
+        return false;
+      }
+    }
+
+    // Ensure that the keys are consecutive integers starting at "0". If eventually we
+    // allow sparse pseudo-arrays, we should check that they are array indices, that is:
+    // `(key >>> 0) + '' === key && key !== "4294967295"`.
+    // Checking the last property first allows us to avoid useless iterations when
+    // there is any property which is not an array index.
+    if(keys.length && keys[keys.length-1] !== keys.length - 1 + '') {
+      return false;
+    }
     for (let key of keys) {
-      let numKey = key >>> 0; // ToUint32(key)
-      if (numKey + '' != key || numKey != length++) {
+      if (key !== (length++) + '') {
         return false;
       }
     }