feat(lib/webidl2): better error messages

lib/webidl2.js

@@ -144,6 +144,7 @@
     // remaining trivia as eof
     tokens.push({
       type: "eof",
+      value: "",
       trivia
     });
 
@@ -210,24 +211,49 @@
 
     function error(str) {
       const maxTokens = 5;
-      const tok = tokens
-        .slice(consume_position, consume_position + maxTokens)
-        .map(t => t.trivia + t.value).join("");
       // Count newlines preceding the actual erroneous token
       if (tokens[consume_position] && !probe("eof")) {
         line += count(tokens[consume_position].trivia, "\n");
       }
 
-      let message;
-      if (current) {
-        message = `Got an error during or right after parsing \`${current.partial ? "partial " : ""}${current.type} ${current.name}\`: ${str}`;
+      const precedingLine = lastLine(
+        tokensToText(sliceTokens(-maxTokens), { precedes: true })
+      );
+
+      const procedingTokens = sliceTokens(maxTokens);
+      const procedingText = tokensToText(procedingTokens);
+      const procedingLine = procedingText.split("\n")[0];
+
+      const spaced = " ".repeat(precedingLine.length) + "^ " + str;
+      const context = precedingLine + procedingLine + "\n" + spaced;
+
+      const since = current ? `, since \`${current.partial ? "partial " : ""}${current.type} ${current.name}\`` : "";
+      const message = `Syntax error at line ${line}${since}:\n${context}`;
+
+      throw new WebIDLParseError(message, line, procedingText, procedingTokens);
+
+      function sliceTokens(count) {
+        return count > 0 ?
+          tokens.slice(consume_position, consume_position + count) :
+          tokens.slice(Math.max(consume_position + count, 0), consume_position);
       }
-      else {
-        // throwing before any valid definition
-        message = `Got an error before parsing any named definition: ${str}`;
+
+      function tokensToText(inputs, { precedes } = {}) {
+        const text = inputs.map(t => t.trivia + t.value).join("");
+        const nextToken = tokens[consume_position];
+        if (nextToken.type === "eof") {
+          return text;
+        }
+        if (precedes) {
+          return text + nextToken.trivia;
+        }
+        return text.slice(nextToken.trivia.length);
       }
 
-      throw new WebIDLParseError(message, line, tok, tokens.slice(0, maxTokens));
+      function lastLine(text) {
+        const splitted = text.split("\n");
+        return splitted[splitted.length - 1];
+      }
     }
 
     function sanitize_name(name, type) {

package.json

@@ -17,7 +17,7 @@
     "mocha": "5.2.0"
   },
   "scripts": {
-    "lint": "eslint lib/*.js test/*.js",
+    "lint": "eslint lib/*.js test/*.js test/util/*.js",
     "test": "npm run lint && mocha",
     "acquire": "node test/util/acquire.js"
   },

test/invalid.js

@@ -8,12 +8,10 @@ const { collect } = require("./util/collect");
 const expect = require("expect");
 
 describe("Parses all of the invalid IDLs to check that they blow up correctly", () => {
-  for (const test of collect("invalid", { expectError: true })) {
+  for (const test of collect("invalid", { expectError: true, raw: true })) {
     it(`should produce the right error for ${test.path}`, () => {
-      const err = test.readJSON();
-      expect(test.error).toBeTruthy();
-      expect(test.error.message).toEqual(err.message);
-      expect(test.error.line).toEqual(err.line);
+      const err = test.readText();
+      expect(test.error.message + "\n").toEqual(err);
     });
   }
 });

test/invalid/baseline/array.txt

@@ -0,0 +1,3 @@
+Syntax error at line 5, since `interface LotteryResults`:
+  readonly attribute unsigned short[][] numbers
+                                   ^ No name in attribute

test/invalid/baseline/caller.txt

@@ -0,0 +1,3 @@
+Syntax error at line 6, since `interface NumberQuadrupler`:
+  legacycaller float compute(float x
+               ^ Invalid operation

test/invalid/baseline/dict-required-default.txt

@@ -0,0 +1,3 @@
+Syntax error at line 4, since `dictionary Dict`:
+  required long member = 0;
+                          ^ Required member must not have a default

test/invalid/baseline/duplicate-escaped.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface Iroha`:
+interface _Iroha {};
+                 ^ The name "Iroha" of type "interface" was already seen

test/invalid/baseline/duplicate.txt

@@ -0,0 +1,3 @@
+Syntax error at line 3, since `typedef Test`:
+interface Test {
+               ^ The name "Test" of type "typedef" was already seen

test/invalid/baseline/enum-bodyless.txt

@@ -0,0 +1,3 @@
+Syntax error at line 1, since `enum X`:
+enum X
+      ^ Bodyless enum

test/invalid/baseline/enum-empty.txt

@@ -0,0 +1,3 @@
+Syntax error at line 1, since `enum Empty`:
+enum Empty {};
+             ^ No value in enum

test/invalid/baseline/enum-wo-comma.txt

@@ -0,0 +1,3 @@
+Syntax error at line 1, since `enum NoComma`:
+enum NoComma { value1 "value2" };
+                      ^ No comma between enum values

test/invalid/baseline/enum.txt

@@ -0,0 +1,3 @@
+Syntax error at line 1, since `enum foo`:
+enum foo { 1, 2, 3
+           ^ Unexpected value in enum

test/invalid/baseline/exception.txt

@@ -0,0 +1,3 @@
+Syntax error at line 4:
+exception SomeException {
+^ Unrecognised tokens

test/invalid/baseline/extattr-empty-ids.txt

@@ -0,0 +1,3 @@
+Syntax error at line 1:
+[Exposed=()]
+          ^ Expected identifiers but none found

test/invalid/baseline/id-underscored-number.txt

@@ -0,0 +1,3 @@
+Syntax error at line 1:
+interface _0 {};
+          ^ No name for interface

test/invalid/baseline/implements.txt

@@ -0,0 +1,3 @@
+Syntax error at line 14, since `interface EventTarget`:
+  Node implements EventTarget;
+  ^ Unrecognised tokens

test/invalid/baseline/implements_and_includes_ws.txt

@@ -0,0 +1,3 @@
+Syntax error at line 4:
+foobar;
+^ Unrecognised tokens

test/invalid/baseline/iterable-empty.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface X`:
+    iterable<>;
+             ^ Error parsing iterable declaration

test/invalid/baseline/iterator.txt

@@ -0,0 +1,3 @@
+Syntax error at line 5, since `interface SessionManager`:
+  Session iterator;
+                  ^ Invalid operation

test/invalid/baseline/legacyiterable.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface LegacyIterable`:
+  legacyiterable<long>;
+  ^ Missing return type

test/invalid/baseline/maplike-1type.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface MapLikeOneType`:
+  maplike<long>;
+              ^ Missing second type argument in maplike declaration

test/invalid/baseline/module.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2:
+module gfx {
+^ Unrecognised tokens

test/invalid/baseline/namespace-readwrite.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `namespace CSS`:
+  attribute object readwrite;
+  ^ Attributes must be readonly in this context

test/invalid/baseline/no-semicolon-callback.txt

@@ -0,0 +1,3 @@
+Syntax error at line 5, since `callback interface NoSemicolon`:
+enum YouNeedOne {
+^ Missing semicolon after interface

test/invalid/baseline/no-semicolon.txt

@@ -0,0 +1,3 @@
+Syntax error at line 5, since `partial interface NoSemicolon`:
+enum YouNeedOne {
+^ Missing semicolon after interface

test/invalid/baseline/nonnullableany.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface NonNullable`:
+  attribute any? foo;
+                 ^ Type any cannot be made nullable

test/invalid/baseline/nonnullableobjects.txt

@@ -0,0 +1,3 @@
+Syntax error at line 4, since `interface NonNullable`:
+  attribute Foo??
+                ^ Can't nullable more than once

test/invalid/baseline/operation-too-special.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface Ako`:
+    getter setter void maki()
+           ^ Missing return type

test/invalid/baseline/promise-nullable.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface X`:
+    attribute Promise<void>?
+                           ^ Promise type cannot be nullable

test/invalid/baseline/promise-with-extended-attribute.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface Foo`:
+  Promise<[XAttr] DOMString>
+          ^ Promise type cannot have extended attribute

test/invalid/baseline/raises.txt

@@ -0,0 +1,3 @@
+Syntax error at line 5, since `interface Person`:
+  attribute DOMString name setraises (InvalidName);
+                           ^ Unterminated attribute

test/invalid/baseline/readonly-iterable.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface ReadonlyIterable`:
+  readonly iterable<long>
+  ^ Missing return type

test/invalid/baseline/record-key-with-extended-attribute.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface Foo`:
+  void foo(record<[XAttr] DOMString,
+                  ^ Record key cannot have extended attribute

test/invalid/baseline/record-key.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface Foo`:
+  void foo(record<octet, any> param
+                  ^ Record key must be a string type

test/invalid/baseline/record-single.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface Foo`:
+ foo(record<DOMString> param);
+                     ^ Missing comma after record key type

test/invalid/baseline/scopedname.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2:
+  typedef gfx::geom::
+             ^ No name in typedef

test/invalid/baseline/sequenceAsAttribute.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface sequenceAsAttribute`:
+  attribute sequence<short> invalid;
+                            ^ Attributes cannot accept sequence types

test/invalid/baseline/setlike-2types.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface SetLikeTwoTypes`:
+  setlike<long, long>;
+              ^ Unterminated setlike declaration

test/invalid/baseline/setter-creator.txt

@@ -0,0 +1,3 @@
+Syntax error at line 3, since `interface OrderedMap`:
+  setter creator void set(DOMString name
+                 ^ Invalid operation

test/invalid/baseline/spaced-negative-infinity.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface X`:
+    const float infinity = - Infinity;
+                           ^ No value for const

test/invalid/baseline/spaced-variadic.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface X`:
+    void operation(object . . . args
+                   ^ Unterminated operation

test/invalid/baseline/special-omittable.txt

@@ -0,0 +1,3 @@
+Syntax error at line 6, since `interface Dictionary`:
+  omittable getter float getProperty(DOMString
+            ^ Invalid operation

test/invalid/baseline/stray-slash.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2:
+/ This is not.
+^ Unrecognised tokens

test/invalid/baseline/stringconstants.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface Util`:
+  const DOMString hello = "world";
+        ^ No type for const

test/invalid/baseline/typedef-nested.txt

@@ -0,0 +1,3 @@
+Syntax error at line 14, since `interface Widget`:
+    typedef sequence<Point>
+    ^ Missing return type

test/invalid/baseline/union-dangling-or.txt

@@ -0,0 +1,3 @@
+Syntax error at line 1:
+ (One or Two or) UnionOr;
+               ^ No type after open parenthesis or 'or' in union type

test/invalid/baseline/union-one.txt

@@ -0,0 +1,3 @@
+Syntax error at line 1:
+typedef (OnlyOne) UnionOne;
+                ^ At least two types are expected in a union type but found less

test/invalid/baseline/union-zero.txt

@@ -0,0 +1,3 @@
+Syntax error at line 1:
+typedef () UnionZero;
+         ^ No type after open parenthesis or 'or' in union type

test/invalid/baseline/unknown-generic.txt

@@ -0,0 +1,3 @@
+Syntax error at line 2, since `interface FetchEvent`:
+  ResponsePromise<any> default(
+                 ^ Unsupported generic type ResponsePromise