From fba165408ce77addc98bf2db455669c4378d34d4 Mon Sep 17 00:00:00 2001
From: Jeremy Ashkenas <jashkenas@gmail.com>
Date: Sat, 18 Dec 2010 13:20:14 -0500
Subject: [PATCH] #923 ... correct interpolation.

---
 lib/lexer.js             | 32 +++++++++++++++-----------------
 src/lexer.coffee         | 27 ++++++++++++++++-----------
 test/test_strings.coffee |  9 +++++++++
 3 files changed, 40 insertions(+), 28 deletions(-)

diff --git a/lib/lexer.js b/lib/lexer.js
index 8982974b..ec8ca92b 100644
--- a/lib/lexer.js
+++ b/lib/lexer.js
@@ -128,7 +128,7 @@
           this.token('STRING', (string = match[0]).replace(MULTILINER, '\\\n'));
           break;
         case '"':
-          if (!(string = this.balancedString(this.chunk, [['"', '"'], ['#{', '}']]))) {
+          if (!(string = this.balancedString(this.chunk, '"', '"'))) {
             return 0;
           }
           if (0 < string.indexOf('#{', 1)) {
@@ -447,32 +447,30 @@
     Lexer.prototype.assignmentError = function() {
       throw SyntaxError("Reserved word \"" + (this.value()) + "\" on line " + (this.line + 1) + " can't be assigned");
     };
-    Lexer.prototype.balancedString = function(str, delimited, options) {
-      var i, open, pair, stack, _i, _len, _ref;
-      if (options == null) {
-        options = {};
-      }
-      stack = [delimited[0]];
+    Lexer.prototype.balancedString = function(str, start, end) {
+      var i, letter, prev, stack, _ref;
+      stack = [end];
       for (i = 1, _ref = str.length; (1 <= _ref ? i < _ref : i > _ref); (1 <= _ref ? i += 1 : i -= 1)) {
-        switch (str.charAt(i)) {
+        switch (letter = str.charAt(i)) {
           case '\\':
             i++;
             continue;
-          case stack[stack.length - 1][1]:
+          case end:
             stack.pop();
             if (!stack.length) {
               return str.slice(0, i + 1);
             }
+            end = stack[stack.length - 1];
             continue;
         }
-        for (_i = 0, _len = delimited.length; _i < _len; _i++) {
-          pair = delimited[_i];
-          if ((open = pair[0]) === str.substr(i, open.length)) {
-            stack.push(pair);
-            i += open.length - 1;
-            break;
-          }
+        if (end === '}' && (letter === '"' || letter === "'")) {
+          stack.push(end = letter);
+        } else if (end === '}' && letter === '{') {
+          stack.push(end = '}');
+        } else if (end === '"' && prev === '#' && letter === '{') {
+          stack.push(end = '}');
         }
+        prev = letter;
       }
       throw new Error("unterminated " + (stack.pop()[0]) + " on line " + (this.line + 1));
     };
@@ -490,7 +488,7 @@
           i += 1;
           continue;
         }
-        if (!(letter === '#' && str.charAt(i + 1) === '{' && (expr = this.balancedString(str.slice(i + 1), [['{', '}']])))) {
+        if (!(letter === '#' && str.charAt(i + 1) === '{' && (expr = this.balancedString(str.slice(i + 1), '#{', '}')))) {
           continue;
         }
         if (pi < i) {
diff --git a/src/lexer.coffee b/src/lexer.coffee
index 5ba012b8..9516a5fc 100644
--- a/src/lexer.coffee
+++ b/src/lexer.coffee
@@ -139,7 +139,7 @@ exports.Lexer = class Lexer
         return 0 unless match = SIMPLESTR.exec @chunk
         @token 'STRING', (string = match[0]).replace MULTILINER, '\\\n'
       when '"'
-        return 0 unless string = @balancedString @chunk, [['"', '"'], ['#{', '}']]
+        return 0 unless string = @balancedString @chunk, '"', '"'
         if 0 < string.indexOf '#{', 1
           @interpolateString string.slice 1, -1
         else
@@ -387,21 +387,26 @@ exports.Lexer = class Lexer
   # a series of delimiters, all of which must be nested correctly within the
   # contents of the string. This method allows us to have strings within
   # interpolations within strings, ad infinitum.
-  balancedString: (str, delimited, options = {}) ->
-    stack = [delimited[0]]
+  balancedString: (str, start, end) ->
+    stack = [end]
     for i in [1...str.length]
-      switch str.charAt i
+      switch letter = str.charAt i
         when '\\'
           i++
           continue
-        when stack[stack.length - 1][1]
+        when end
           stack.pop()
-          return str.slice 0, i + 1 unless stack.length
+          unless stack.length
+            return str.slice 0, i + 1
+          end = stack[stack.length - 1]
           continue
-      for pair in delimited when (open = pair[0]) is str.substr i, open.length
-        stack.push pair
-        i += open.length - 1
-        break
+      if end is '}' and letter in ['"', "'"]
+        stack.push end = letter
+      else if end is '}' and letter is '{'
+        stack.push end = '}'
+      else if end is '"' and prev is '#' and letter is '{'
+        stack.push end = '}'
+      prev = letter
     throw new Error "unterminated #{ stack.pop()[0] } on line #{ @line + 1 }"
 
 
@@ -423,7 +428,7 @@ exports.Lexer = class Lexer
         i += 1
         continue
       unless letter is '#' and str.charAt(i+1) is '{' and
-             (expr = @balancedString str.slice(i+1), [['{', '}']])
+             (expr = @balancedString str.slice(i + 1), '#{', '}')
         continue
       tokens.push ['NEOSTRING', str.slice(pi, i)] if pi < i
       inner = expr.slice(1, -1)
diff --git a/test/test_strings.coffee b/test/test_strings.coffee
index cbbe29ac..63e2a451 100644
--- a/test/test_strings.coffee
+++ b/test/test_strings.coffee
@@ -107,3 +107,12 @@ eq 'multiline nested "interpolations" work', """multiline #{
     "\"interpolations\""
   }"
 } work"""
+
+
+# Issue #923: Tricky interpolation.
+eq "#{ "{" }", "{"
+
+eq "#{ '#{}}' } }", '#{}} }'
+
+eq "#{"'#{ ({a: "b#{1}"}['a']) }'"}", "'b1'"
+