1 files changed, 78 insertions, 0 deletions
diff --git a/devtools/client/debugger/src/reducers/exceptions.js b/devtools/client/debugger/src/reducers/exceptions.js
new file mode 100644
index 0000000000..a4a26de5df
--- /dev/null
+++ b/devtools/client/debugger/src/reducers/exceptions.js
@@ -0,0 +1,78 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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/>. */
+
+/**
+ * Exceptions reducer
+ * @module reducers/exceptionss
+ */
+
+export function initialExceptionsState() {
+  return {
+    // Store exception objects created by actions/exceptions.js's addExceptionFromResources()
+    // This is keyed by source actor id, and values are arrays of exception objects.
+    mutableExceptionsMap: new Map(),
+  };
+}
+
+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 = mutableExceptionsMap.get(sourceActorId);
+  if (!exceptions) {
+    exceptions = [];
+    mutableExceptionsMap.set(sourceActorId, exceptions);
+  } else if (
+    exceptions.some(({ lineNumber, columnNumber }) => {
+      return (
+        lineNumber == exception.lineNumber &&
+        columnNumber == exception.columnNumber
+      );
+    })
+  ) {
+    // Avoid adding duplicated exceptions for the same line/column
+    return state;
+  }
+
+  // As these arrays are only used by getSelectedSourceExceptions selector method,
+  // which coalesce multiple arrays and always return new array instance,
+  // it isn't important to clone these array in case of modification.
+  exceptions.push(exception);
+
+  return {
+    ...state,
+  };
+}
+
+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;