Bug 1094939 - Preferences actor should throw with the name for an unknown preference. r=ochameau

Differential Revision: https://phabricator.services.mozilla.com/D50728

--HG--
extra : moz-landing-system : lando

devtools/server/actors/preference.js

@@ -4,11 +4,19 @@
 
 "use strict";
 
-const { Ci } = require("chrome");
 const protocol = require("devtools/shared/protocol");
 const Services = require("Services");
 const { preferenceSpec } = require("devtools/shared/specs/preference");
 
+const { PREF_STRING, PREF_INT, PREF_BOOL } = Services.prefs;
+
+function ensurePrefType(name, expectedType) {
+  const type = Services.prefs.getPrefType(name);
+  if (type !== expectedType) {
+    throw new Error(`preference is not of the right type: ${name}`);
+  }
+}
+
 /**
  * Normally the preferences are set using Services.prefs, but this actor allows
  * a debugger client to set preferences on the debuggee. This is particularly useful
@@ -23,14 +31,17 @@ var PreferenceActor = protocol.ActorClassWithSpec(preferenceSpec, {
   typeName: "preference",
 
   getBoolPref: function(name) {
+    ensurePrefType(name, PREF_BOOL);
     return Services.prefs.getBoolPref(name);
   },
 
   getCharPref: function(name) {
+    ensurePrefType(name, PREF_STRING);
     return Services.prefs.getCharPref(name);
   },
 
   getIntPref: function(name) {
+    ensurePrefType(name, PREF_INT);
     return Services.prefs.getIntPref(name);
   },
 
@@ -41,13 +52,13 @@ var PreferenceActor = protocol.ActorClassWithSpec(preferenceSpec, {
       try {
         let value;
         switch (Services.prefs.getPrefType(name)) {
-          case Ci.nsIPrefBranch.PREF_STRING:
+          case PREF_STRING:
             value = Services.prefs.getCharPref(name);
             break;
-          case Ci.nsIPrefBranch.PREF_INT:
+          case PREF_INT:
             value = Services.prefs.getIntPref(name);
             break;
-          case Ci.nsIPrefBranch.PREF_BOOL:
+          case PREF_BOOL:
             value = Services.prefs.getBoolPref(name);
             break;
           default:

devtools/server/tests/mochitest/test_preference.html

@@ -77,6 +77,21 @@ function runTests() {
       });
     }
 
+    function checkUndefined() {
+      let next = p.getCharPref("test.undefined");
+      next = next.then(
+        () => ok(false, "getCharPref should've thrown for an undefined preference"),
+        (ex) => {
+          is(
+            ex,
+            "Protocol error (unknownError): preference is not of the right type: test.undefined",
+            "getCharPref should throw an exception with the preference name"
+          );
+        }
+      );
+      return next;
+    }
+
     function updatePrefsProperty(key) {
       return function(value) {
         prefs[key] = value;
@@ -93,6 +108,7 @@ function runTests() {
     .then(() => p.clearUserPref("test.bool"))
     .then(() => p.clearUserPref("test.int"))
     .then(() => p.clearUserPref("test.string"))
+    .then(() => checkUndefined())
     .then(checkValues);
   });
 }