From 37fceda7e8c60c7908dc099d9413bf2dd7c2daf3 Mon Sep 17 00:00:00 2001
From: Caitlin Potter <caitpotter88@gmail.com>
Date: Tue, 16 Jun 2015 11:24:29 -0500
Subject: [PATCH] chore(broccoli): improve `overwrite` error in merge-trees

Modified the error message to include the relative duplicate path,
to help in diagnosing the cause of the error message.

Closes #2521
---
 tools/broccoli/broccoli-merge-trees.spec.ts |  8 ++++++--
 tools/broccoli/broccoli-merge-trees.ts      | 11 ++++++++---
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/tools/broccoli/broccoli-merge-trees.spec.ts b/tools/broccoli/broccoli-merge-trees.spec.ts
index 8e5f5a5d35..c1c659f546 100644
--- a/tools/broccoli/broccoli-merge-trees.spec.ts
+++ b/tools/broccoli/broccoli-merge-trees.spec.ts
@@ -55,7 +55,9 @@ describe('MergeTrees', () => {
     let treeDiffer = MakeTreeDiffers(['tree1', 'tree2', 'tree3']);
     let treeMerger = mergeTrees(['tree1', 'tree2', 'tree3'], 'dest', {});
     expect(() => treeMerger.rebuild(treeDiffer.diffTrees()))
-        .toThrowError("`overwrite` option is required for handling duplicates.");
+        .toThrowError(
+            'Duplicate path found while merging trees. Path: "foo.js".\n' +
+            'Either remove the duplicate or enable the "overwrite" option for this merge.');
 
     testDir = {
       'tree1': {'foo.js': mockfs.file({content: 'tree1/foo.js content', mtime: new Date(1000)})},
@@ -82,6 +84,8 @@ describe('MergeTrees', () => {
     testDir.tree2['foo.js'] = mockfs.file({content: 'tree2/foo.js content', mtime: new Date(1000)});
     mockfs(testDir);
     expect(() => treeMerger.rebuild(treeDiffer.diffTrees()))
-        .toThrowError("`overwrite` option is required for handling duplicates.");
+        .toThrowError(
+            'Duplicate path found while merging trees. Path: "foo.js".\n' +
+            'Either remove the duplicate or enable the "overwrite" option for this merge.');
   });
 });
diff --git a/tools/broccoli/broccoli-merge-trees.ts b/tools/broccoli/broccoli-merge-trees.ts
index ac2e6043ec..b749e4c92f 100644
--- a/tools/broccoli/broccoli-merge-trees.ts
+++ b/tools/broccoli/broccoli-merge-trees.ts
@@ -16,6 +16,11 @@ function outputFileSync(sourcePath, destPath) {
   symlinkOrCopySync(sourcePath, destPath);
 }
 
+function pathOverwrittenError(path) {
+  const msg = 'Either remove the duplicate or enable the "overwrite" option for this merge.';
+  return new Error(`Duplicate path found while merging trees. Path: "${path}".\n${msg}`);
+}
+
 export class MergeTrees implements DiffingBroccoliPlugin {
   private pathCache: {[key: string]: number[]} = Object.create(null);
   public options: MergeTreesOptions;
@@ -59,7 +64,7 @@ export class MergeTrees implements DiffingBroccoliPlugin {
             // ASSERT(contains(pathsToEmit, changedPath));
             cache.unshift(index);
           } else {
-            throw new Error("`overwrite` option is required for handling duplicates.");
+            throw pathOverwrittenError(changedPath);
           }
         });
       });
@@ -79,7 +84,7 @@ export class MergeTrees implements DiffingBroccoliPlugin {
               this.pathCache[removedPath] = undefined;
             } else if (!emitted[removedPath]) {
               if (cache.length === 1 && !overwrite) {
-                throw new Error("`overwrite` option is required for handling duplicates.");
+                throw pathOverwrittenError(removedPath);
               }
               emit(removedPath);
             }
@@ -102,7 +107,7 @@ export class MergeTrees implements DiffingBroccoliPlugin {
             cache.push(index);
             cache.sort((a, b) => a - b);
             if (cache.length > 1 && !overwrite) {
-              throw new Error("`overwrite` option is required for handling duplicates.");
+              throw pathOverwrittenError(changedPath);
             }
             if (cache[cache.length - 1] === index && !emitted[changedPath]) {
               emit(changedPath);