Allow computed class properties (#5206)

* fix broken JS output

* static computed properties

lib/coffeescript/grammar.js

@@ -298,6 +298,12 @@
       function() {
         return new Value(new ComputedPropertyName($2));
       }),
+      o('@ [ Expression ]',
+      function() {
+        return new Value(LOC(1)(new ThisLiteral($1)),
+      [LOC(3)(new ComputedPropertyName($3))],
+      'this');
+      }),
       o('AlphaNumeric')
     ],
     // Object literal spread properties.

lib/coffeescript/nodes.js

@@ -2993,7 +2993,7 @@
               // The class scope is not available yet, so return the assignment to update later
               assign = this.externalCtor = new Assign(new Value, value);
             } else if (!assign.variable.this) {
-              name = new (base.shouldCache() ? Index : Access)(base);
+              name = base instanceof ComputedPropertyName ? new Index(base.value) : new (base.shouldCache() ? Index : Access)(base);
               prototype = new Access(new PropertyName('prototype'));
               variable = new Value(new ThisLiteral(), [prototype, name]);
               assign.variable = variable;

lib/coffeescript/rewriter.js

@@ -196,16 +196,23 @@
       // The lexer has tagged the opening bracket of an indexing operation call.
       // Match it with its paired close.
       closeOpenIndexes() {
-        var action, condition;
+        var action, condition, startToken;
+        startToken = null;
         condition = function(token, i) {
           var ref;
           return (ref = token[0]) === ']' || ref === 'INDEX_END';
         };
         action = function(token, i) {
-          return token[0] = 'INDEX_END';
+          if (this.tokens.length >= i && this.tokens[i + 1][0] === ':') {
+            startToken[0] = '[';
+            return token[0] = ']';
+          } else {
+            return token[0] = 'INDEX_END';
+          }
         };
         return this.scanTokens(function(token, i) {
           if (token[0] === 'INDEX_START') {
+            startToken = token;
             this.detectEnd(i + 1, condition, action);
           }
           return 1;
@@ -281,7 +288,7 @@
         stack = [];
         start = null;
         return this.scanTokens(function(token, i, tokens) {
-          var endImplicitCall, endImplicitObject, forward, implicitObjectContinues, inControlFlow, inImplicit, inImplicitCall, inImplicitControl, inImplicitObject, isImplicit, isImplicitCall, isImplicitObject, k, newLine, nextTag, nextToken, offset, prevTag, prevToken, ref, ref1, ref2, s, sameLine, stackIdx, stackItem, stackTag, stackTop, startIdx, startImplicitCall, startImplicitObject, startsLine, tag;
+          var endImplicitCall, endImplicitObject, forward, implicitObjectContinues, inControlFlow, inImplicit, inImplicitCall, inImplicitControl, inImplicitObject, isImplicit, isImplicitCall, isImplicitObject, k, newLine, nextTag, nextToken, offset, prevTag, prevToken, ref, ref1, ref2, s, sameLine, stackIdx, stackItem, stackTag, stackTop, startIdx, startImplicitCall, startImplicitObject, startIndex, startTag, startsLine, tag;
           [tag] = token;
           [prevTag] = prevToken = i > 0 ? tokens[i - 1] : [];
           [nextTag] = nextToken = i < tokens.length - 1 ? tokens[i + 1] : [];
@@ -481,7 +488,13 @@
               var ref1;
               switch (false) {
                 case ref1 = this.tag(i - 1), indexOf.call(EXPRESSION_END, ref1) < 0:
-                  return start[1];
+                  [startTag, startIndex] = start;
+                  if (startTag === '[' && startIndex > 0 && this.tag(startIndex - 1) === '@' && !tokens[startIndex - 1].spaced) {
+                    return startIndex - 1;
+                  } else {
+                    return startIndex;
+                  }
+                  break;
                 case this.tag(i - 2) !== '@':
                   return i - 2;
                 default:

src/grammar.coffee

@@ -222,6 +222,7 @@ grammar =
   ObjAssignable: [
     o 'SimpleObjAssignable'
     o '[ Expression ]',          -> new Value new ComputedPropertyName $2
+    o '@ [ Expression ]',        -> new Value LOC(1)(new ThisLiteral $1), [LOC(3)(new ComputedPropertyName($3))], 'this'
     o 'AlphaNumeric'
   ]
 

src/nodes.coffee

@@ -2007,7 +2007,11 @@ exports.ExecutableClassBody = class ExecutableClassBody extends Base
         # The class scope is not available yet, so return the assignment to update later
         assign = @externalCtor = new Assign new Value, value
       else if not assign.variable.this
-        name      = new (if base.shouldCache() then Index else Access) base
+        name =
+          if base instanceof ComputedPropertyName
+            new Index base.value
+          else
+            new (if base.shouldCache() then Index else Access) base
         prototype = new Access new PropertyName 'prototype'
         variable  = new Value new ThisLiteral(), [ prototype, name ]
 

src/rewriter.coffee

@@ -118,14 +118,21 @@ exports.Rewriter = class Rewriter
   # The lexer has tagged the opening bracket of an indexing operation call.
   # Match it with its paired close.
   closeOpenIndexes: ->
+    startToken = null
     condition = (token, i) ->
       token[0] in [']', 'INDEX_END']
 
     action = (token, i) ->
-      token[0] = 'INDEX_END'
+      if @tokens.length >= i and @tokens[i + 1][0] is ':'
+        startToken[0] = '['
+        token[0] = ']'
+      else
+        token[0] = 'INDEX_END'
 
     @scanTokens (token, i) ->
-      @detectEnd i + 1, condition, action if token[0] is 'INDEX_START'
+      if token[0] is 'INDEX_START'
+        startToken = token
+        @detectEnd i + 1, condition, action
       1
 
   # Match tags in token stream starting at `i` with `pattern`.
@@ -321,7 +328,12 @@ exports.Rewriter = class Rewriter
       if tag is ':'
         # Go back to the (implicit) start of the object.
         s = switch
-          when @tag(i - 1) in EXPRESSION_END then start[1]
+          when @tag(i - 1) in EXPRESSION_END
+            [startTag, startIndex] = start
+            if startTag is '[' and startIndex > 0 and @tag(startIndex - 1) is '@' and not tokens[startIndex - 1].spaced
+              startIndex - 1
+            else
+              startIndex
           when @tag(i - 2) is '@' then i - 2
           else i - 1
 

test/classes.coffee

@@ -1935,3 +1935,20 @@ test "#5085: Bug: @ reference to class not maintained in do block", ->
 
   eq thisFoo, 'foo assigned in class'
   eq thisBar, 'foo assigned in class'
+
+test "#5204: Computed class property", ->
+  foo = 'bar'
+  class A
+    [foo]: 'baz'
+  a = new A()
+  eq a.bar, 'baz'
+  eq A::bar, 'baz'
+
+test "#5204: Static computed class property", ->
+  foo = 'bar'
+  qux = 'quux'
+  class A
+    @[foo]: 'baz'
+    @[qux]: -> 3
+  eq A.bar, 'baz'
+  eq A.quux(), 3

test/error_messages.coffee

@@ -855,6 +855,13 @@ test "invalid object keys", ->
     {a=2}
       ^
   '''
+  assertErrorFormat '''
+    @[a]: 1
+  ''', '''
+    [stdin]:1:1: error: invalid object key
+    @[a]: 1
+    ^^^^
+  '''
 
 test "invalid destructuring default target", ->
   assertErrorFormat '''

test/objects.coffee

@@ -903,3 +903,6 @@ test "#4579: Postfix for/while/until in first line of implicit object literals",
       baz: 1337
   arrayEq [4, 3, 2, 1, 0], six.foo.bar
   eq 1337, six.foo.baz
+
+test "#5204: not parsed as static property", ->
+  doesNotThrow -> CoffeeScript.compile "@ [b]: 2"