making the lexer more sophisticated about incorrect outdents ... a little safer for everyone.

lib/lexer.js

@@ -54,6 +54,8 @@
       // The current line.
       this.indent = 0;
       // The current indentation level.
+      this.outdebt = 0;
+      // The under-outdentation of the last outdent.
       this.indents = [];
       // The stack of all current indentation levels.
       this.tokens = [];
@@ -321,10 +323,17 @@
     // inwards past several recorded indents.
     Lexer.prototype.outdent_token = function(move_out, no_newlines) {
       var last_indent;
-      while (move_out > 0 && this.indents.length) {
-        last_indent = this.indents.pop();
-        this.token('OUTDENT', last_indent);
-        move_out -= last_indent;
+      if (move_out > -this.outdebt) {
+        while (move_out > 0 && this.indents.length) {
+          last_indent = this.indents.pop();
+          this.token('OUTDENT', last_indent);
+          move_out -= last_indent;
+        }
+      } else {
+        this.outdebt += move_out;
+      }
+      if (!(no_newlines)) {
+        this.outdebt = move_out;
       }
       if (!(this.tag() === 'TERMINATOR' || no_newlines)) {
         this.token('TERMINATOR', "\n");

src/lexer.coffee

@@ -46,6 +46,7 @@ exports.Lexer: class Lexer
     @i       : 0            # Current character position we're parsing.
     @line    : o.line or 0  # The current line.
     @indent  : 0            # The current indentation level.
+    @outdebt : 0            # The under-outdentation of the last outdent.
     @indents : []           # The stack of all current indentation levels.
     @tokens  : []           # Stream of parsed tokens in the form ['TYPE', value, line]
     while @i < @code.length
@@ -218,10 +219,14 @@ exports.Lexer: class Lexer
   # Record an outdent token or multiple tokens, if we happen to be moving back
   # inwards past several recorded indents.
   outdent_token: (move_out, no_newlines) ->
-    while move_out > 0 and @indents.length
-      last_indent: @indents.pop()
-      @token 'OUTDENT', last_indent
-      move_out: - last_indent
+    if move_out > -@outdebt
+      while move_out > 0 and @indents.length
+        last_indent: @indents.pop()
+        @token 'OUTDENT', last_indent
+        move_out: - last_indent
+    else
+      @outdebt: + move_out
+    @outdebt: move_out unless no_newlines
     @token 'TERMINATOR', "\n" unless @tag() is 'TERMINATOR' or no_newlines
     true
 

test/test_blocks.coffee

@@ -22,4 +22,14 @@ counter
   .tick ->
     1
 
-ok results.join(' ') is '3 2 1'
+ok results.join(' ') is '3 2 1'
+
+
+# Make incorrect indentation safe.
+func: ->
+  obj: {
+      key: 10
+    }
+  obj.key - 5
+
+ok func() is 5