make Headers follow spec (#1427)

js/headers.ts

@@ -31,10 +31,11 @@ class HeadersBase {
   // https://github.com/bitinn/node-fetch/blob/master/src/headers.js
   // Copyright (c) 2016 David Frank. MIT License.
   private _validateName(name: string) {
-    if (invalidTokenRegex.test(name)) {
+    if (invalidTokenRegex.test(name) || name === "") {
       throw new TypeError(`${name} is not a legal HTTP header name`);
     }
   }
+
   private _validateValue(value: string) {
     if (invalidHeaderCharRegex.test(value)) {
       throw new TypeError(`${value} is not a legal HTTP header value`);
@@ -51,8 +52,17 @@ class HeadersBase {
     } else {
       this[headerMap] = new Map();
       if (Array.isArray(init)) {
-        for (const [rawName, rawValue] of init) {
-          const [name, value] = this._normalizeParams(rawName, rawValue);
+        for (const tuple of init) {
+          // If header does not contain exactly two items,
+          // then throw a TypeError.
+          // ref: https://fetch.spec.whatwg.org/#concept-headers-fill
+          if (tuple.length !== 2) {
+            // tslint:disable:max-line-length
+            // prettier-ignore
+            throw new TypeError("Failed to construct 'Headers'; Each header pair must be an iterable [name, value] tuple");
+          }
+
+          const [name, value] = this._normalizeParams(tuple[0], tuple[1]);
           this._validateName(name);
           this._validateValue(value);
           const existingValue = this[headerMap].get(name);

js/headers_test.ts

@@ -224,11 +224,34 @@ test(function headerIllegalReject() {
   } catch (e) {
     errorCount++;
   }
-  assertEqual(errorCount, 8);
+  try {
+    headers.set("", "ok");
+  } catch (e) {
+    errorCount++;
+  }
+  assertEqual(errorCount, 9);
   // 'o k' is valid value but invalid name
   new Headers({ "He-y": "o k" });
 });
 
+// If pair does not contain exactly two items,then throw a TypeError.
+test(function headerParamsShouldThrowTypeError() {
+  let hasThrown = 0;
+
+  try {
+    new Headers(([["1"]] as unknown) as Array<[string, string]>);
+    hasThrown = 1;
+  } catch (err) {
+    if (err instanceof TypeError) {
+      hasThrown = 2;
+    } else {
+      hasThrown = 3;
+    }
+  }
+
+  assertEqual(hasThrown, 2);
+});
+
 test(function headerParamsArgumentsCheck() {
   const methodRequireOneParam = ["delete", "get", "has", "forEach"];