fix: throw "no cloud event detected" if one can't be read

This commit changes the event mode detection in `HTTPReceiver` so that it will
throw a TypeError if the event mode can't be detected per the spec.

Signed-off-by: Lance Ball <[email protected]>

Author: lance

lib/bindings/http/http_receiver.js

@@ -35,10 +35,14 @@ class HTTPReceiver {
 }
 
 function getMode(headers) {
-  let mode = "binary";
+  let mode = "unknown";
   const contentType = headers[constants.HEADER_CONTENT_TYPE];
   if (contentType && contentType.startsWith(constants.MIME_CE)) {
     mode = "structured";
+  } else if (headers[constants.BINARY_HEADERS_1.ID]) {
+    mode = "binary";
+  } else {
+    throw new TypeError("no cloud event detected");
   }
   return mode;
 }

test/bindings/http/promiscuous_receiver_test.js

@@ -11,6 +11,22 @@ const data = {
 };
 
 describe("HTTP Transport Binding Receiver for CloudEvents", () => {
+  describe("HTTP CloudEvent format detection", () => {
+    const specversion = "1.0";
+    it("Throws when the event format cannot be detected", () => {
+      const payload = {
+        id,
+        type,
+        source,
+        data,
+        specversion
+      };
+
+      expect(receiver.accept.bind(receiver, {}, payload))
+        .to.throw("no cloud event detected");
+    });
+  });
+
   describe("V1", () => {
     const specversion = "1.0";