Fix empty label handling

As discovered in jsdom/whatwg-url#250, the library currently does not handle empty labels in the same way that browsers seem to do. Although the standard is unclear, we should align to browser handling.

To test this, we pull in the new IdnaTestV2.json file from WPT. This is somewhat redundant with our existing IdnaTestV2.txt, but it also represents a significant curation effort to ensure we only have URL-applicable tests, so we should make use of that.

index.js

@@ -130,7 +130,9 @@ function validateLabel(label, { checkHyphens, checkBidi, checkJoiners, processin
   }
 
   // https://tools.ietf.org/html/rfc5893#section-2
-  if (checkBidi) {
+  // For the codePoints length check, see discussion in https://github.com/jsdom/whatwg-url/pull/250 and the second item
+  // in https://github.com/whatwg/url/issues/744.
+  if (checkBidi && codePoints.length > 0) {
     let rtl;
 
     // 1

scripts/getLatestTests.js

@@ -24,7 +24,12 @@ async function main() {
     })(),
     (async () => {
       const asciiTarget = fs.createWriteStream(path.resolve(__dirname, "../test/fixtures/toascii.json"));
-      const response = await fetch("https://github.com/web-platform-tests/wpt/raw/112ad5ca55d55f6da2ccc7468e6dcc91b4e5d223/url/resources/toascii.json");
+      const response = await fetch("https://github.com/web-platform-tests/wpt/raw/7234ceaeb1505c42bef05a88a77da930653a4e31/url/resources/toascii.json");
+      await pipelinePromise(response.body, asciiTarget);
+    })(),
+    (async () => {
+      const asciiTarget = fs.createWriteStream(path.resolve(__dirname, "../test/fixtures/IdnaTestV2ToASCII.json"));
+      const response = await fetch("https://github.com/web-platform-tests/wpt/raw/7234ceaeb1505c42bef05a88a77da930653a4e31/url/resources/IdnaTestV2.json");
       await pipelinePromise(response.body, asciiTarget);
     })()
   ]);

test/toascii.js

@@ -5,6 +5,7 @@ const assert = require("assert");
 const tr46 = require("../index.js");
 
 const toASCIITestCases = require("./fixtures/toascii.json");
+const idnaTestV2 = require("./fixtures/IdnaTestV2ToASCII.json");
 
 function testToASCII(testCase) {
   return () => {
@@ -29,7 +30,29 @@ describe("ToASCII", () => {
 
     let description = testCase.input;
     if (testCase.comment) {
-      description = ` (${testCase.comment})`;
+      description += ` (${testCase.comment})`;
+    }
+
+    specify(description, testToASCII(testCase));
+  }
+});
+
+describe("ToASCII via IdnaTestV2.json in wpt", () => {
+  for (const testCase of idnaTestV2) {
+    if (typeof testCase === "string") {
+      // It's a "comment"; skip it.
+      continue;
+    }
+
+    if (testCase.input.includes("?")) {
+      // ToASCII will not fail on these. But, the URL Standard will. IdnaTestV2.json is mostly focused on the URL
+      // Standard, so it expects failures. We should skip them.
+      continue;
+    }
+
+    let description = testCase.input;
+    if (testCase.comment) {
+      description += ` (${testCase.comment})`;
     }
 
     specify(description, testToASCII(testCase));