From 0598b7275b4e8f7342ade785de920867961e32ef Mon Sep 17 00:00:00 2001
From: Alan Pierce <alangpierce@gmail.com>
Date: Wed, 27 Jul 2016 23:16:30 -0700
Subject: [PATCH] fix: properly set location data in OUTDENT nodes

Backport of https://github.com/jashkenas/coffeescript/pull/4291 .

In f609036beef3aa1529c210ffad3ced818ee94cce, a line was changed from
`if length > 0 then (length - 1) else 0` to `Math.max 0, length - 1`. However,
in some cases, the `length` variable can be `undefined`. The previous code would
correctly compute `lastCharacter` as 0, but the new code would compute it as
`NaN`. This would cause trouble later on: the end location would just be the end
of the current chunk, which would be incorrect.

Here's a specific case where the parser was behaving incorrectly:
```
a {
  b: ->
    return c d,
      if e
        f
}
g
```

The OUTDENT tokens after the `f` had an undefined length, so the `NaN` made it
so the end location was at the end of the file. That meant that various nodes in
the AST, like the `return` node, would incorrectly have an end location at the
end of the file.

To fix, I just reverted the change to that particular line.

Also add a test that tokens have locations that are in order
---
 lib/coffee-script/lexer.js |  2 +-
 src/lexer.coffee           |  2 +-
 test/location.coffee       | 19 +++++++++++++++++++
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/lib/coffee-script/lexer.js b/lib/coffee-script/lexer.js
index 857bf29bec..de9632f977 100644
--- a/lib/coffee-script/lexer.js
+++ b/lib/coffee-script/lexer.js
@@ -764,7 +764,7 @@
       }
       locationData = {};
       ref2 = this.getLineAndColumnFromChunk(offsetInChunk), locationData.first_line = ref2[0], locationData.first_column = ref2[1];
-      lastCharacter = Math.max(0, length - 1);
+      lastCharacter = length > 0 ? length - 1 : 0;
       ref3 = this.getLineAndColumnFromChunk(offsetInChunk + lastCharacter), locationData.last_line = ref3[0], locationData.last_column = ref3[1];
       token = [tag, value, locationData];
       return token;
diff --git a/src/lexer.coffee b/src/lexer.coffee
index 48a1e8564f..773c9c775d 100644
--- a/src/lexer.coffee
+++ b/src/lexer.coffee
@@ -649,7 +649,7 @@ exports.Lexer = class Lexer
 
     # Use length - 1 for the final offset - we're supplying the last_line and the last_column,
     # so if last_column == first_column, then we're looking at a character of length 1.
-    lastCharacter = Math.max 0, length - 1
+    lastCharacter = if length > 0 then (length - 1) else 0
     [locationData.last_line, locationData.last_column] =
       @getLineAndColumnFromChunk offsetInChunk + lastCharacter
 
diff --git a/test/location.coffee b/test/location.coffee
index 783b44afbd..35b9584c51 100644
--- a/test/location.coffee
+++ b/test/location.coffee
@@ -450,6 +450,25 @@ test "#3621: Multiline regex and manual `Regex` call with interpolation should
       eq tokenA.origin?[1], tokenB.origin?[1]
     eq tokenA.stringEnd, tokenB.stringEnd
 
+test "Verify tokens have locations that are in order", ->
+  source = '''
+    a {
+      b: ->
+        return c d,
+          if e
+            f
+    }
+    g
+  '''
+  tokens = CoffeeScript.tokens source
+  lastToken = null
+  for token in tokens
+    if lastToken
+      ok token[2].first_line >= lastToken[2].last_line
+      if token[2].first_line == lastToken[2].last_line
+        ok token[2].first_column >= lastToken[2].last_column
+    lastToken = token
+
 test "Verify all tokens get a location", ->
   doesNotThrow ->
     tokens = CoffeeScript.tokens testScript