fix: do not assume an empty content-type header is JSON (#444)

The parser for HTTP binary made the assumption that if there was no `content-type`
header in the incoming message, it should inject `application/json`. Discussion
about the rationale for this is in https://github.com/cloudevents/sdk-javascript/issues/441.

This commit, removes that injection and adds a test to ensure the bytes are
simply not parsed, but just passed along untouched.

Fixes: https://github.com/cloudevents/sdk-javascript/issues/441

Signed-off-by: Lance Ball <lball@redhat.com>

src/message/http/headers.ts

@@ -65,11 +65,6 @@ export function sanitize(headers: Headers): Headers {
     .filter((header) => Object.hasOwnProperty.call(headers, header))
     .forEach((header) => (sanitized[header.toLowerCase()] = headers[header]));
 
-  // If no content-type header is sent, assume application/json
-  if (!sanitized[CONSTANTS.HEADER_CONTENT_TYPE]) {
-    sanitized[CONSTANTS.HEADER_CONTENT_TYPE] = CONSTANTS.MIME_JSON;
-  }
-
   return sanitized;
 }
 

test/integration/message_test.ts

@@ -41,6 +41,21 @@ const imageData = new Uint32Array(fs.readFileSync(path.join(process.cwd(), "test
 const image_base64 = asBase64(imageData);
 
 describe("HTTP transport", () => {
+  it("Handles events with no content-type and no datacontenttype", () => {
+    const body = "{Something[Not:valid}JSON";
+    const message: Message = {
+      body,
+      headers: {
+        "ce-source": "/test/type",
+        "ce-type": "test.type",
+        "ce-id": "1234",
+      },
+    };
+    const event: CloudEvent = HTTP.toEvent(message);
+    expect(event.data).to.equal(body);
+    expect(event.datacontentype).to.equal(undefined);
+  });
+
   it("Can detect invalid CloudEvent Messages", () => {
     // Create a message that is not an actual event
     const message: Message = {