From 8c2f737fe0b7ce8bd435290fcee5b2c65823fce4 Mon Sep 17 00:00:00 2001
From: Ruben Verborgh <ruben@verborgh.org>
Date: Tue, 26 Jan 2021 10:03:29 +0100
Subject: [PATCH] feat: Set MS-Author-Via header.

Closes https://github.com/solid/community-server/issues/539
---
 config/presets/ldp/response-writer.json        |  9 +++++++++
 config/presets/middleware.json                 |  1 +
 test/integration/LdpHandlerWithoutAuth.test.ts |  1 +
 test/integration/Middleware.test.ts            | 12 ++++++++++++
 4 files changed, 23 insertions(+)

diff --git a/config/presets/ldp/response-writer.json b/config/presets/ldp/response-writer.json
index 71bb9f1757..be65859824 100644
--- a/config/presets/ldp/response-writer.json
+++ b/config/presets/ldp/response-writer.json
@@ -5,6 +5,15 @@
       "@id": "urn:solid-server:default:MetadataSerializer",
       "@type": "SequenceHandler",
       "SequenceHandler:_handlers": [
+        {
+          "@type": "ConstantMetadataWriter",
+          "ConstantMetadataWriter:_headers": [
+            {
+              "ConstantMetadataWriter:_headers_key": "MS-Author-Via",
+              "ConstantMetadataWriter:_headers_value": "SPARQL"
+            }
+          ]
+        },
         {
           "@type": "MappedMetadataWriter",
           "MappedMetadataWriter:_headerMap": [
diff --git a/config/presets/middleware.json b/config/presets/middleware.json
index e1aa24a0eb..e82f72ebf7 100644
--- a/config/presets/middleware.json
+++ b/config/presets/middleware.json
@@ -19,6 +19,7 @@
           "CorsHandler:_options_credentials": true,
           "CorsHandler:_options_exposedHeaders": [
             "Location",
+            "MS-Author-Via",
             "Updates-Via"
           ]
         },
diff --git a/test/integration/LdpHandlerWithoutAuth.test.ts b/test/integration/LdpHandlerWithoutAuth.test.ts
index f8cf0b1096..cb137aa13b 100644
--- a/test/integration/LdpHandlerWithoutAuth.test.ts
+++ b/test/integration/LdpHandlerWithoutAuth.test.ts
@@ -81,6 +81,7 @@ describe.each(stores)('An LDP handler without auth using %s', (name, { storeUrn,
     expect(response.statusCode).toBe(200);
     expect(response._getBuffer().toString()).toContain('TESTFILE0');
     expect(response.getHeaders().link).toBe(`<${LDP.Resource}>; rel="type"`);
+    expect(response.getHeaders()['ms-author-via']).toBe('SPARQL');
 
     // DELETE
     await resourceHelper.deleteResource(id);
diff --git a/test/integration/Middleware.test.ts b/test/integration/Middleware.test.ts
index ad73836ad5..19f569b0cc 100644
--- a/test/integration/Middleware.test.ts
+++ b/test/integration/Middleware.test.ts
@@ -92,6 +92,18 @@ describe('An Express server with middleware', (): void => {
     expect(exposed.split(/\s*,\s*/u)).toContain('Location');
   });
 
+  it('exposes the MS-Author-Via header via CORS.', async(): Promise<void> => {
+    const res = await request(server).get('/').expect(200);
+    const exposed = res.header['access-control-expose-headers'];
+    expect(exposed.split(/\s*,\s*/u)).toContain('MS-Author-Via');
+  });
+
+  it('exposes the Updates-Via header via CORS.', async(): Promise<void> => {
+    const res = await request(server).get('/').expect(200);
+    const exposed = res.header['access-control-expose-headers'];
+    expect(exposed.split(/\s*,\s*/u)).toContain('Updates-Via');
+  });
+
   it('sends incoming requests to the handler.', async(): Promise<void> => {
     const response = request(server).get('/').set('Host', 'test.com');
     expect(response).toBeDefined();