Reorganize trailing comma code a bit.

- Split out syntax error tests.
- Avoid redundant handling of empty literals.

script/test.py

@@ -230,8 +230,10 @@ class Test:
       index += 1
 
 
-  def fail(self, message, *args, **kwargs):
-    self.failures.append(message.format(*args, **kwargs))
+  def fail(self, message, *args):
+    if args:
+      message = message.format(*args)
+    self.failures.append(message)
 
 
 def color_text(text, color):

src/vm/wren_compiler.c

@@ -1809,27 +1809,26 @@ static void list(Compiler* compiler, bool allowAssignment)
   // Instantiate a new list.
   callMethod(compiler, 0, "new()", 5);
 
+  ignoreNewlines(compiler);
+  
   // Compile the list elements. Each one compiles to a ".add()" call.
-  if (peek(compiler) != TOKEN_RIGHT_BRACKET)
+  do
   {
-    do
-    {
-      ignoreNewlines(compiler);
+    ignoreNewlines(compiler);
 
-      // List with trailing comma.
-      if (peek(compiler) == TOKEN_RIGHT_BRACKET) break;
+    // Stop if we hit the end of the list.
+    if (peek(compiler) == TOKEN_RIGHT_BRACKET) break;
 
-      // Push a copy of the list since the add() call will consume it.
-      emit(compiler, CODE_DUP);
+    // Push a copy of the list since the add() call will consume it.
+    emit(compiler, CODE_DUP);
 
-      // The element.
-      expression(compiler);
-      callMethod(compiler, 1, "add(_)", 6);
+    // The element.
+    expression(compiler);
+    callMethod(compiler, 1, "add(_)", 6);
 
-      // Discard the result of the add() call.
-      emit(compiler, CODE_POP);
-    } while (match(compiler, TOKEN_COMMA));
-  }
+    // Discard the result of the add() call.
+    emit(compiler, CODE_POP);
+  } while (match(compiler, TOKEN_COMMA));
 
   // Allow newlines before the closing ']'.
   ignoreNewlines(compiler);
@@ -1850,31 +1849,28 @@ static void map(Compiler* compiler, bool allowAssignment)
 
   // Compile the map elements. Each one is compiled to just invoke the
   // subscript setter on the map.
-  if (peek(compiler) != TOKEN_RIGHT_BRACE)
+  do
   {
-    do
-    {
-      ignoreNewlines(compiler);
+    ignoreNewlines(compiler);
 
-      // Map with trailing comma.
-      if (peek(compiler) == TOKEN_RIGHT_BRACE) break;
+    // Stop if we hit the end of the map.
+    if (peek(compiler) == TOKEN_RIGHT_BRACE) break;
 
-      // Push a copy of the map since the subscript call will consume it.
-      emit(compiler, CODE_DUP);
+    // Push a copy of the map since the subscript call will consume it.
+    emit(compiler, CODE_DUP);
 
-      // The key.
-      parsePrecedence(compiler, false, PREC_PRIMARY);
-      consume(compiler, TOKEN_COLON, "Expect ':' after map key.");
+    // The key.
+    parsePrecedence(compiler, false, PREC_PRIMARY);
+    consume(compiler, TOKEN_COLON, "Expect ':' after map key.");
+    ignoreNewlines(compiler);
 
-      // The value.
-      expression(compiler);
+    // The value.
+    expression(compiler);
+    callMethod(compiler, 2, "[_]=(_)", 7);
 
-      callMethod(compiler, 2, "[_]=(_)", 7);
-
-      // Discard the result of the setter call.
-      emit(compiler, CODE_POP);
-    } while (match(compiler, TOKEN_COMMA));
-  }
+    // Discard the result of the setter call.
+    emit(compiler, CODE_POP);
+  } while (match(compiler, TOKEN_COMMA));
 
   // Allow newlines before the closing '}'.
   ignoreNewlines(compiler);

test/language/list/duplicate_comma.wren

@@ -0,0 +1 @@
+[1,,2] // expect error

test/language/list/duplicate_trailing_comma.wren

@@ -0,0 +1 @@
+[1,,] // expect error

test/language/list/empty_list_with_comma.wren

@@ -0,0 +1 @@
+[,] // expect error

test/language/list/newlines.wren

@@ -8,3 +8,17 @@ var list = [
 
 IO.print(list[0]) // expect: a
 IO.print(list[1]) // expect: b
+
+// Newline after trailing comma.
+list = ["c",
+
+]
+
+IO.print(list[0]) // expect: c
+
+// Newline in empty list.
+list = [
+
+]
+
+IO.print(list.count) // expect: 0

test/language/list/trailing_comma.wren

@@ -1,12 +1,4 @@
-var list = [
-  "a",
-  "b",
-]
+var list = ["a", "b",]
 
 IO.print(list[0]) // expect: a
 IO.print(list[1]) // expect: b
-
-// Invalid syntax
-IO.print(new Fiber { Meta.eval("[,]")    }.try()) // expect: Could not compile source code.
-IO.print(new Fiber { Meta.eval("[1,,]")  }.try()) // expect: Could not compile source code.
-IO.print(new Fiber { Meta.eval("[1,,2]") }.try()) // expect: Could not compile source code.

test/language/map/duplicate_comma.wren

@@ -0,0 +1 @@
+{1:1,,2:2} // expect error

test/language/map/duplicate_trailing_comma.wren

@@ -0,0 +1 @@
+{1:1,,} // expect error

test/language/map/empty_map_with_comma.wren

@@ -0,0 +1 @@
+{,} // expect error

test/language/map/newlines.wren

@@ -0,0 +1,27 @@
+// Allow after '{', ':', and ',', and before ']'.
+var map = {
+
+"a":
+
+"a value",
+
+"b": "b value"
+
+}
+
+IO.print(map["a"]) // expect: a value
+IO.print(map["b"]) // expect: b value
+
+// Newline after trailing comma.
+map = {"c": "c value",
+
+}
+
+IO.print(map["c"]) // expect: c value
+
+// Newline in empty map.
+map = {
+
+}
+
+IO.print(map.count) // expect: 0

test/language/map/trailing_comma.wren

@@ -5,9 +5,3 @@ var map = {
 
 IO.print(map["a"]) // expect: 1
 IO.print(map["b"]) // expect: 2
-
-// Invalid syntax
-// Parentheses are necessary to have these interpret as maps and not as blocks.
-IO.print(new Fiber { Meta.eval("({,})")        }.try()) // expect: Could not compile source code.
-IO.print(new Fiber { Meta.eval("({1:1,,})")    }.try()) // expect: Could not compile source code.
-IO.print(new Fiber { Meta.eval("({1:1,,2:2})") }.try()) // expect: Could not compile source code.