Add support for checking the event payload

README.md

@@ -53,6 +53,21 @@ try {
 }
 ```
 
+### Matching arbitrary payloads
+
+In addition to checking the event, you can also check for entries in the provided `GITHUB_EVENT`.
+
+Here's an example that will throw if the pull request was not opened by `mheap`:
+
+```javascript
+guard({
+  event: "pull_request.opened",
+  payload: { user: { login: "mheap" } },
+});
+```
+
+See https://docs.github.com/en/developers/webhooks-and-events/webhooks/webhook-events-and-payloads for sample payloads
+
 ### Matching multiple conditions
 
 You can provide multiple conditions to validate. If all fail, an `Error` will be thrown.

index.js

@@ -1,3 +1,5 @@
+const _ = require("lodash");
+
 module.exports = (guards) => {
   if (!Array.isArray(guards)) {
     guards = [guards];
@@ -59,5 +61,31 @@ function runSingle(params) {
     };
   }
 
+  if (params.payload) {
+    const expectedPayload = params.payload;
+    if (!payloadIncludes(payload, expectedPayload)) {
+      return {
+        success: false,
+        reason: `Invalid payload. Expected '${JSON.stringify(
+          expectedPayload
+        )}', got '${JSON.stringify(payload)}'`,
+      };
+    }
+  }
   return { success: true };
 }
+
+function payloadIncludes(base, object) {
+  function changes(object, base) {
+    return _.transform(object, function (result, value, key) {
+      if (!_.isEqual(value, base[key])) {
+        result[key] =
+          _.isObject(value) && _.isObject(base[key])
+            ? changes(value, base[key])
+            : value;
+      }
+    });
+  }
+
+  return _.isEmpty(changes(object, base));
+}

index.test.js

@@ -76,6 +76,46 @@ describe("Action Guard", () => {
     });
   });
 
+  describe("Arbitrary payload conditions", () => {
+    it("throws if the required fields are different in the payload", () => {
+      mockEvent("pull_request", { user: { login: "fake_user" } });
+      expect(() => {
+        guard({
+          event: "pull_request",
+          payload: { user: { login: "mheap" } },
+        });
+      }).toThrow(
+        new Error(
+          `Invalid payload. Expected '{"user":{"login":"mheap"}}', got '{"user":{"login":"fake_user"}}'`
+        )
+      );
+    });
+
+    it("throws if the required fields are not in the payload", () => {
+      mockEvent("pull_request", { user: { email: "user@example.com" } });
+      expect(() => {
+        guard({
+          event: "pull_request",
+          payload: { user: { login: "mheap" } },
+        });
+      }).toThrow(
+        new Error(
+          `Invalid payload. Expected '{"user":{"login":"mheap"}}', got '{"user":{"email":"user@example.com"}}'`
+        )
+      );
+    });
+
+    it("does not throw if the payload matches", () => {
+      mockEvent("pull_request", { user: { login: "mheap" } });
+      expect(
+        guard({
+          event: "pull_request",
+          payload: { user: { login: "mheap" } },
+        })
+      ).toBe(undefined);
+    });
+  });
+
   describe("Calling formats", () => {
     it("string", () => {
       mockEvent("pull_request", { action: "opened" });