Bug 1559717 - Fix displaying getter value for getter returning falsy values. r=davidwalsh.

We were displaying result.value.throw if result.value.return
was falsy. But it can happen that a getter does return a
falsy value, and we want to display it.
So now we turn the expression the other way around, we first
check result.value.throw, and then default to result.value.return.
A mochitest is added to ensure we hav expected value for different
getters returning falsy values.

Differential Revision: https://phabricator.services.mozilla.com/D39136

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

devtools/client/debugger/packages/devtools-reps/src/object-inspector/reducer.js

@@ -58,7 +58,7 @@ function reducer(
         getterValue:
           data.result &&
           data.result.value &&
-          (data.result.value.return || data.result.value.throw),
+          (data.result.value.throw || data.result.value.return),
       }),
     });
   }

devtools/client/shared/components/reps/reps.js

@@ -2352,7 +2352,7 @@ function reducer(state = initialState(), action = {}) {
     return cloneState({
       actors: data.actor ? new Set(state.actors || []).add(data.result.from) : state.actors,
       evaluations: new Map(state.evaluations).set(data.node.path, {
-        getterValue: data.result && data.result.value && (data.result.value.return || data.result.value.throw)
+        getterValue: data.result && data.result.value && (data.result.value.throw || data.result.value.return)
       })
     });
   }

devtools/client/webconsole/test/mochitest/browser_webconsole_object_inspector_getters.js

@@ -35,6 +35,18 @@ add_task(async function() {
           get myNullGetter() {
             return null;
           },
+          get myZeroGetter() {
+            return 0;
+          },
+          get myEmptyStringGetter() {
+            return "";
+          },
+          get myFalseGetter() {
+            return false;
+          },
+          get myTrueGetter() {
+            return true;
+          },
           get myObjectGetter() {
             return { foo: "bar" };
           },
@@ -73,6 +85,10 @@ add_task(async function() {
   await testNumberGetter(oi);
   await testUndefinedGetter(oi);
   await testNullGetter(oi);
+  await testZeroGetter(oi);
+  await testEmptyStringGetter(oi);
+  await testFalseGetter(oi);
+  await testTrueGetter(oi);
   await testObjectGetter(oi);
   await testArrayGetter(oi);
   await testMapGetter(oi);
@@ -201,6 +217,126 @@ async function testNullGetter(oi) {
   );
 }
 
+async function testZeroGetter(oi) {
+  let node = findObjectInspectorNode(oi, "myZeroGetter");
+  is(
+    isObjectInspectorNodeExpandable(node),
+    false,
+    "The node can't be expanded"
+  );
+  const invokeButton = getObjectInspectorInvokeGetterButton(node);
+  ok(invokeButton, "There is an invoke button as expected");
+
+  invokeButton.click();
+  await waitFor(
+    () =>
+      !getObjectInspectorInvokeGetterButton(
+        findObjectInspectorNode(oi, "myZeroGetter")
+      )
+  );
+
+  node = findObjectInspectorNode(oi, "myZeroGetter");
+  ok(
+    node.textContent.includes(`myZeroGetter: 0`),
+    "0 getter now has the expected text content"
+  );
+  is(
+    isObjectInspectorNodeExpandable(node),
+    false,
+    "The node can't be expanded"
+  );
+}
+
+async function testEmptyStringGetter(oi) {
+  let node = findObjectInspectorNode(oi, "myEmptyStringGetter");
+  is(
+    isObjectInspectorNodeExpandable(node),
+    false,
+    "The node can't be expanded"
+  );
+  const invokeButton = getObjectInspectorInvokeGetterButton(node);
+  ok(invokeButton, "There is an invoke button as expected");
+
+  invokeButton.click();
+  await waitFor(
+    () =>
+      !getObjectInspectorInvokeGetterButton(
+        findObjectInspectorNode(oi, "myEmptyStringGetter")
+      )
+  );
+
+  node = findObjectInspectorNode(oi, "myEmptyStringGetter");
+  ok(
+    node.textContent.includes(`myEmptyStringGetter: ""`),
+    "empty string getter now has the expected text content"
+  );
+  is(
+    isObjectInspectorNodeExpandable(node),
+    false,
+    "The node can't be expanded"
+  );
+}
+
+async function testFalseGetter(oi) {
+  let node = findObjectInspectorNode(oi, "myFalseGetter");
+  is(
+    isObjectInspectorNodeExpandable(node),
+    false,
+    "The node can't be expanded"
+  );
+  const invokeButton = getObjectInspectorInvokeGetterButton(node);
+  ok(invokeButton, "There is an invoke button as expected");
+
+  invokeButton.click();
+  await waitFor(
+    () =>
+      !getObjectInspectorInvokeGetterButton(
+        findObjectInspectorNode(oi, "myFalseGetter")
+      )
+  );
+
+  node = findObjectInspectorNode(oi, "myFalseGetter");
+  ok(
+    node.textContent.includes(`myFalseGetter: false`),
+    "false getter now has the expected text content"
+  );
+  is(
+    isObjectInspectorNodeExpandable(node),
+    false,
+    "The node can't be expanded"
+  );
+}
+
+async function testTrueGetter(oi) {
+  let node = findObjectInspectorNode(oi, "myTrueGetter");
+  is(
+    isObjectInspectorNodeExpandable(node),
+    false,
+    "The node can't be expanded"
+  );
+  const invokeButton = getObjectInspectorInvokeGetterButton(node);
+  ok(invokeButton, "There is an invoke button as expected");
+
+  invokeButton.click();
+  await waitFor(
+    () =>
+      !getObjectInspectorInvokeGetterButton(
+        findObjectInspectorNode(oi, "myTrueGetter")
+      )
+  );
+
+  node = findObjectInspectorNode(oi, "myTrueGetter");
+  ok(
+    node.textContent.includes(`myTrueGetter: true`),
+    "false getter now has the expected text content"
+  );
+  is(
+    isObjectInspectorNodeExpandable(node),
+    false,
+    "The node can't be expanded"
+  );
+}
+
 async function testObjectGetter(oi) {
   let node = findObjectInspectorNode(oi, "myObjectGetter");
   is(