From ffb488f81fe6787b6aac4db7798e96d7da9b9cb8 Mon Sep 17 00:00:00 2001
From: Julian Rosse <julian@helixbass.net>
Date: Thu, 6 Apr 2017 15:08:09 -0400
Subject: [PATCH] Fix #4487: Outdentation bug

---
 lib/coffee-script/lexer.js |  9 +++------
 src/lexer.coffee           |  9 +++------
 test/formatting.coffee     | 17 +++++++++++++++++
 3 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/lib/coffee-script/lexer.js b/lib/coffee-script/lexer.js
index c87dc96349..26d6577141 100644
--- a/lib/coffee-script/lexer.js
+++ b/lib/coffee-script/lexer.js
@@ -471,12 +471,9 @@
         lastIndent = this.indents[this.indents.length - 1];
         if (!lastIndent) {
           moveOut = 0;
-        } else if (lastIndent === this.outdebt) {
-          moveOut -= this.outdebt;
-          this.outdebt = 0;
-        } else if (lastIndent < this.outdebt) {
-          this.outdebt -= lastIndent;
-          moveOut -= lastIndent;
+        } else if (this.outdebt && moveOut <= this.outdebt) {
+          this.outdebt -= moveOut;
+          moveOut = 0;
         } else {
           dent = this.indents.pop() + this.outdebt;
           if (outdentLength && (ref2 = this.chunk[outdentLength], indexOf.call(INDENTABLE_CLOSERS, ref2) >= 0)) {
diff --git a/src/lexer.coffee b/src/lexer.coffee
index df10eaa98b..bfa6ec9a54 100644
--- a/src/lexer.coffee
+++ b/src/lexer.coffee
@@ -402,12 +402,9 @@ exports.Lexer = class Lexer
       lastIndent = @indents[@indents.length - 1]
       if not lastIndent
         moveOut = 0
-      else if lastIndent is @outdebt
-        moveOut -= @outdebt
-        @outdebt = 0
-      else if lastIndent < @outdebt
-        @outdebt -= lastIndent
-        moveOut  -= lastIndent
+      else if @outdebt and moveOut <= @outdebt
+        @outdebt -= moveOut
+        moveOut   = 0
       else
         dent = @indents.pop() + @outdebt
         if outdentLength and @chunk[outdentLength] in INDENTABLE_CLOSERS
diff --git a/test/formatting.coffee b/test/formatting.coffee
index 31cc282840..d340ba709f 100644
--- a/test/formatting.coffee
+++ b/test/formatting.coffee
@@ -254,3 +254,20 @@ test "#1275: allow indentation before closing brackets", ->
     a = 1
    )
   eq 1, a
+
+test "#4487: Handle unusual outdentation", ->
+  a =
+    switch 1
+      when 2
+          no
+         when 3 then no
+      when 1 then yes
+  eq yes, a
+
+  b = do ->
+    if no
+      if no
+            1
+       2
+      3
+  eq b, undefined