From 3fb22f123a9d64187105160664c6e4ea083eb040 Mon Sep 17 00:00:00 2001
From: Kevin Sawicki <kevin@github.com>
Date: Thu, 18 Sep 2014 11:03:11 -0700
Subject: [PATCH] Don't throw errors when folding comments

Previously trying to fold single line comments at the start/end
of files would throw errors since the +1 and -1 used in the
index ranges would cause the loop to advance past the last row
or before the first row.
---
 spec/language-mode-spec.coffee | 22 ++++++++++++++++++++++
 src/language-mode.coffee       | 21 +++++++++++++--------
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/spec/language-mode-spec.coffee b/spec/language-mode-spec.coffee
index fd3a4a478..f6f0ebdd7 100644
--- a/spec/language-mode-spec.coffee
+++ b/spec/language-mode-spec.coffee
@@ -70,6 +70,28 @@ describe "LanguageMode", ->
         expect(languageMode.rowRangeForCodeFoldAtBufferRow(2)).toBeNull()
         expect(languageMode.rowRangeForCodeFoldAtBufferRow(4)).toEqual [4, 7]
 
+    describe ".rowRangeForCommentAtBufferRow(bufferRow)", ->
+      it "returns the start/end rows of the foldable comment starting at the given row", ->
+        buffer.setText("//this is a multi line comment\n//another line")
+        expect(languageMode.rowRangeForCommentAtBufferRow(0)).toEqual [0, 1]
+        expect(languageMode.rowRangeForCommentAtBufferRow(1)).toEqual [0, 1]
+
+        buffer.setText("//this is a multi line comment\n//another line\n//and one more")
+        expect(languageMode.rowRangeForCommentAtBufferRow(0)).toEqual [0, 2]
+        expect(languageMode.rowRangeForCommentAtBufferRow(1)).toEqual [0, 2]
+
+        buffer.setText("//this is a multi line comment\n\n//with an empty line")
+        expect(languageMode.rowRangeForCommentAtBufferRow(0)).toBeUndefined()
+        expect(languageMode.rowRangeForCommentAtBufferRow(1)).toBeUndefined()
+        expect(languageMode.rowRangeForCommentAtBufferRow(2)).toBeUndefined()
+
+        buffer.setText("//this is a single line comment\n")
+        expect(languageMode.rowRangeForCommentAtBufferRow(0)).toBeUndefined()
+        expect(languageMode.rowRangeForCommentAtBufferRow(1)).toBeUndefined()
+
+        buffer.setText("//this is a single line comment")
+        expect(languageMode.rowRangeForCommentAtBufferRow(0)).toBeUndefined()
+
     describe "suggestedIndentForBufferRow", ->
       it "returns the suggested indentation based on auto-indent/outdent rules", ->
         expect(languageMode.suggestedIndentForBufferRow(0)).toBe 0
diff --git a/src/language-mode.coffee b/src/language-mode.coffee
index de1a5b928..6ce4b7b3a 100644
--- a/src/language-mode.coffee
+++ b/src/language-mode.coffee
@@ -148,15 +148,20 @@ class LanguageMode
     return unless @editor.displayBuffer.tokenizedBuffer.tokenizedLineForRow(bufferRow).isComment()
 
     startRow = bufferRow
-    for currentRow in [bufferRow-1..0]
-      break if @buffer.isRowBlank(currentRow)
-      break unless @editor.displayBuffer.tokenizedBuffer.tokenizedLineForRow(currentRow).isComment()
-      startRow = currentRow
     endRow = bufferRow
-    for currentRow in [bufferRow+1..@buffer.getLastRow()]
-      break if @buffer.isRowBlank(currentRow)
-      break unless @editor.displayBuffer.tokenizedBuffer.tokenizedLineForRow(currentRow).isComment()
-      endRow = currentRow
+
+    if bufferRow > 0
+      for currentRow in [bufferRow-1..0]
+        break if @buffer.isRowBlank(currentRow)
+        break unless @editor.displayBuffer.tokenizedBuffer.tokenizedLineForRow(currentRow).isComment()
+        startRow = currentRow
+
+    if bufferRow < @buffer.getLastRow()
+      for currentRow in [bufferRow+1..@buffer.getLastRow()]
+        break if @buffer.isRowBlank(currentRow)
+        break unless @editor.displayBuffer.tokenizedBuffer.tokenizedLineForRow(currentRow).isComment()
+        endRow = currentRow
+
     return [startRow, endRow] if startRow isnt endRow
 
   rowRangeForCodeFoldAtBufferRow: (bufferRow) ->