feat: support raw Set-Cookie headers

README.md

@@ -37,6 +37,7 @@
   - [HTTP/2 Server Push](#http2-server-push)
   - [Force HTTP/1(.1) protocol](#force-http11-protocol)
   - [HTTP/1.1 Keep-Alive](#http11-keep-alive)
+  - [Extract Set-Cookie Header](#extract-set-cookie-header)
   - [Self-signed Certificates](#self-signed-certificates)
   - [Set cache size limit](#set-cache-size-limit)
   - [Disable caching](#disable-caching)
@@ -455,6 +456,18 @@ const resp = await fetch('https://httpbin.org/status/200');
 console.log(`Connection: ${resp.headers.get('connection')}`); // -> keep-alive
 ```
 
+### Extract Set-Cookie Header
+
+Unlike browsers, you can access raw `Set-Cookie` headers manually using `Headers.plain()`. This is an `@adobe/fetch` only API.
+
+```javascript
+const { fetch } = require('@adobe/fetch');
+
+const resp = await fetch('https://httpbin.org/cookies/set?a=1&b=2');
+// returns an array of values, instead of a string of comma-separated values
+console.log(resp.headers.plain()['set-cookie']);
+```
+
 ### Self-signed Certificates
 
 ```javascript

src/fetch/headers.js

@@ -79,11 +79,25 @@ class Headers {
       });
     } else if (Array.isArray(init)) {
       init.forEach(([name, value]) => {
-        this.append(name, value);
+        if (Array.isArray(value)) {
+          // special case for Set-Cookie header which can have an array of values
+          value.forEach((val) => {
+            this.append(name, val);
+          });
+        } else {
+          this.append(name, value);
+        }
       });
     } else /* istanbul ignore else  */ if (isPlainObject(init)) {
       for (const [name, value] of Object.entries(init)) {
-        this.append(name, value);
+        if (Array.isArray(value)) {
+          // special case for Set-Cookie header which can have an array of values
+          value.forEach((val) => {
+            this.append(name, val);
+          });
+        } else {
+          this.set(name, value);
+        }
       }
     }
   }
@@ -98,14 +112,26 @@ class Headers {
 
   get(name) {
     const val = this[INTERNALS].map.get(normalizeName(name));
-    return val === undefined ? null : val;
+    if (val === undefined) {
+      return null;
+    } else if (Array.isArray(val)) {
+      return val.join(', ');
+    } else {
+      return val;
+    }
   }
 
   append(name, value) {
     const nm = normalizeName(name);
     const val = normalizeValue(value, name);
     const oldVal = this[INTERNALS].map.get(nm);
-    this[INTERNALS].map.set(nm, oldVal ? `${oldVal}, ${val}` : val);
+    if (Array.isArray(oldVal)) {
+      oldVal.push(val);
+    } else if (oldVal === undefined) {
+      this[INTERNALS].map.set(nm, val);
+    } else {
+      this[INTERNALS].map.set(nm, [oldVal, val]);
+    }
   }
 
   delete(name) {

test/fetch/headers.test.js

@@ -61,6 +61,7 @@ describe('Headers Tests', () => {
       ['c', '4'],
       ['b', '3'],
       ['a', '1'],
+      ['d', ['5', '6']],
     ]);
     expect(headers).to.have.property('forEach');
 
@@ -73,6 +74,7 @@ describe('Headers Tests', () => {
       ['a', '1'],
       ['b', '2, 3'],
       ['c', '4'],
+      ['d', '5, 6'],
     ]);
   });
 
@@ -154,8 +156,9 @@ describe('Headers Tests', () => {
   });
 
   it('constructor should support plain object', () => {
-    const headers = new Headers({ foo: 'bar' });
+    const headers = new Headers({ foo: 'bar', 'x-cookies': ['a=1', 'b=2'] });
     expect(headers.get('foo')).to.be.equal('bar');
+    expect(headers.get('x-cookies')).to.be.equal('a=1, b=2');
   });
 
   it('get should return null if not found', () => {
@@ -181,8 +184,16 @@ describe('Headers Tests', () => {
   });
 
   it('plain() should return plain object representation', () => {
-    const hdrObj = { foo: 'bar' };
+    const hdrObj = { foo: 'bar', 'x-cookies': ['a=1', 'b=2'] };
     const headers = new Headers(hdrObj);
     expect(headers.plain()).to.be.deep.equal(hdrObj);
   });
+
+  it('should support multi-valued headers (e.g. Set-Cookie)', () => {
+    const headers = new Headers();
+    headers.set('set-cookie', 'a=1; Path=/');
+    headers.append('set-cookie', 'b=2; Path=/');
+    expect(headers.get('set-cookie')).to.be.equal('a=1; Path=/, b=2; Path=/');
+    expect(headers.plain()['set-cookie']).to.be.deep.equal(['a=1; Path=/', 'b=2; Path=/']);
+  });
 });

test/fetch/index.test.js

@@ -601,6 +601,17 @@ testParams.forEach((params) => {
       assert.deepStrictEqual(reqForm, searchParams);
     });
 
+    it('returns Set-Cookie headers', async () => {
+      const resp = await fetch(`${baseUrl}/cookies/set?a=1&b=2`, { redirect: 'manual' });
+      // Response headers:
+      // set-cookie: a=1; [Secure; ]Path=/
+      // set-cookie: b=2; [Secure; ]Path=/
+      assert.strictEqual(resp.status, 302);
+      assert(/a=1; (Secure; )?Path=\/, b=2; (Secure; )?Path=\//.test(resp.headers.get('set-cookie')));
+      assert(/a=1; (Secure; )?Path=\//.test(resp.headers.plain()['set-cookie'][0]));
+      assert(/b=2; (Secure; )?Path=\//.test(resp.headers.plain()['set-cookie'][1]));
+    });
+
     if (protocol === 'https') {
       it('supports self signed certificate', async () => {
         const server = new Server(httpVersion === '2.0' ? 2 : 1, true, HELLO_WORLD);