1 files changed, 132 insertions, 0 deletions
diff --git a/devtools/client/debugger/src/workers/parser/findOutOfScopeLocations.js b/devtools/client/debugger/src/workers/parser/findOutOfScopeLocations.js
new file mode 100644
index 0000000000..25b5042dd1
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+++ b/devtools/client/debugger/src/workers/parser/findOutOfScopeLocations.js
@@ -0,0 +1,132 @@
+/* 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/>. */
+
+import { containsLocation, containsPosition } from "./utils/contains";
+
+import { getSymbols } from "./getSymbols";
+
+function findSymbols(source) {
+  const { functions, comments } = getSymbols(source);
+  return { functions, comments };
+}
+
+/**
+ * Returns the location for a given function path. If the path represents a
+ * function declaration, the location will begin after the function identifier
+ * but before the function parameters.
+ */
+
+function getLocation(func) {
+  const location = { ...func.location };
+
+  // if the function has an identifier, start the block after it so the
+  // identifier is included in the "scope" of its parent
+  const identifierEnd = func?.identifier?.loc?.end;
+  if (identifierEnd) {
+    location.start = identifierEnd;
+  }
+
+  return location;
+}
+
+/**
+ * Find the nearest location containing the input position and
+ * return inner locations under that nearest location
+ *
+ * @param {Array<Object>} locations Notice! The locations MUST be sorted by `sortByStart`
+ *                  so that we can do linear time complexity operation.
+ * @returns {Array<Object>}
+ */
+function getInnerLocations(locations, position) {
+  // First, let's find the nearest position-enclosing function location,
+  // which is to find the last location enclosing the position.
+  let parentIndex;
+  for (let i = locations.length - 1; i >= 0; i--) {
+    const loc = locations[i];
+    if (containsPosition(loc, position)) {
+      parentIndex = i;
+      break;
+    }
+  }
+
+  if (parentIndex == undefined) {
+    return [];
+  }
+  const parentLoc = locations[parentIndex];
+
+  // Then, from the nearest location, loop locations again and put locations into
+  // the innerLocations array until we get to a location not enclosed by the nearest location.
+  const innerLocations = [];
+  for (let i = parentIndex + 1; i < locations.length; i++) {
+    const loc = locations[i];
+    if (!containsLocation(parentLoc, loc)) {
+      break;
+    }
+
+    innerLocations.push(loc);
+  }
+
+  return innerLocations;
+}
+
+/**
+ * Return an new locations array which excludes
+ * items that are completely enclosed by another location in the input locations
+ *
+ * @param locations Notice! The locations MUST be sorted by `sortByStart`
+ *                  so that we can do linear time complexity operation.
+ */
+function removeOverlaps(locations) {
+  if (!locations.length) {
+    return [];
+  }
+  const firstParent = locations[0];
+  return locations.reduce(deduplicateNode, [firstParent]);
+}
+
+function deduplicateNode(nodes, location) {
+  const parent = nodes[nodes.length - 1];
+  if (!containsLocation(parent, location)) {
+    nodes.push(location);
+  }
+  return nodes;
+}
+
+/**
+ * Sorts an array of locations by start position
+ */
+function sortByStart(a, b) {
+  if (a.start.line < b.start.line) {
+    return -1;
+  } else if (a.start.line === b.start.line) {
+    return a.start.column - b.start.column;
+  }
+
+  return 1;
+}
+
+/**
+ * Returns an array of locations that are considered out of scope for the given
+ * location.
+ */
+function findOutOfScopeLocations(sourceId, position) {
+  const { functions, comments } = findSymbols(sourceId);
+  const commentLocations = comments.map(c => c.location);
+  const locations = functions
+    .map(getLocation)
+    .concat(commentLocations)
+    .sort(sortByStart);
+
+  const innerLocations = getInnerLocations(locations, position);
+  const outerLocations = locations.filter(loc => {
+    if (innerLocations.includes(loc)) {
+      return false;
+    }
+
+    return !containsPosition(loc, position);
+  });
+  return removeOverlaps(outerLocations);
+}
+
+export default findOutOfScopeLocations;