Bug 1822293 - [devtools] Clear exceptions reducer on each thread remo…

…val. r=devtools-reviewers,nchevobbe

This help reduce memory footprint, especially in the MBT,
but will also help stop clearing all reducers on navigation.

Differential Revision: https://phabricator.services.mozilla.com/D175331

devtools/client/debugger/src/actions/exceptions.js

@@ -20,6 +20,7 @@ export function addExceptionFromResources(resources) {
         sourceActorId: sourceId,
         errorMessage,
         stacktrace,
+        threadActorId: resource.targetFront.targetForm.threadActor,
       };
 
       dispatch(addException(exception));

devtools/client/debugger/src/reducers/exceptions.js

@@ -19,18 +19,22 @@ function update(state = initialExceptionsState(), action) {
   switch (action.type) {
     case "ADD_EXCEPTION":
       return updateExceptions(state, action);
+    case "REMOVE_THREAD": {
+      return removeExceptionsFromThread(state, action);
+    }
   }
   return state;
 }
 
 function updateExceptions(state, action) {
+  const { mutableExceptionsMap } = state;
   const { exception } = action;
   const { sourceActorId } = exception;
 
-  let exceptions = state.mutableExceptionsMap.get(sourceActorId);
+  let exceptions = mutableExceptionsMap.get(sourceActorId);
   if (!exceptions) {
     exceptions = [];
-    state.mutableExceptionsMap.set(sourceActorId, exceptions);
+    mutableExceptionsMap.set(sourceActorId, exceptions);
   }
 
   // As these arrays are only used by getSelectedSourceExceptions selector method,
@@ -43,4 +47,22 @@ function updateExceptions(state, action) {
   };
 }
 
+function removeExceptionsFromThread(state, action) {
+  const { mutableExceptionsMap } = state;
+  const { threadActorID } = action;
+  const sizeBefore = mutableExceptionsMap.size;
+  for (const [sourceActorId, exceptions] of mutableExceptionsMap) {
+    // All exceptions relates to the same source actor, and so, the same thread actor.
+    if (exceptions[0].threadActorId == threadActorID) {
+      mutableExceptionsMap.delete(sourceActorId);
+    }
+  }
+  if (sizeBefore != mutableExceptionsMap.size) {
+    return {
+      ...state,
+    };
+  }
+  return state;
+}
+
 export default update;