Provide better errors for unsupported event types (#68)

* Validate event type during restore

* PR Feedback

* Format

* Linting

src/constants.ts

@@ -12,3 +12,9 @@ export enum State {
     CacheKey = "CACHE_KEY",
     CacheResult = "CACHE_RESULT"
 }
+
+export enum Events {
+    Key = "GITHUB_EVENT_NAME",
+    Push = "push",
+    PullRequest = "pull_request"
+}

src/restore.ts

@@ -3,12 +3,22 @@ import { exec } from "@actions/exec";
 import * as io from "@actions/io";
 import * as path from "path";
 import * as cacheHttpClient from "./cacheHttpClient";
-import { Inputs, State } from "./constants";
+import { Events, Inputs, State } from "./constants";
 import * as utils from "./utils/actionUtils";
 
 async function run(): Promise<void> {
     try {
         // Validate inputs, this can cause task failure
+        if (!utils.isValidEvent()) {
+            core.setFailed(
+                `Event Validation Error: The event type ${
+                    process.env[Events.Key]
+                } is not supported. Only ${utils
+                    .getSupportedEvents()
+                    .join(", ")} events are supported at this time.`
+            );
+        }
+
         let cachePath = utils.resolvePath(
             core.getInput(Inputs.Path, { required: true })
         );

src/utils/actionUtils.ts

@@ -4,7 +4,8 @@ import * as fs from "fs";
 import * as os from "os";
 import * as path from "path";
 import * as uuidV4 from "uuid/v4";
-import { Outputs, State } from "../constants";
+
+import { Events, Outputs, State } from "../constants";
 import { ArtifactCacheEntry } from "../contracts";
 
 // From https://github.com/actions/toolkit/blob/master/packages/tool-cache/src/tool-cache.ts#L23
@@ -83,3 +84,15 @@ export function resolvePath(filePath: string): string {
 
     return path.resolve(filePath);
 }
+
+export function getSupportedEvents(): string[] {
+    return [Events.Push, Events.PullRequest];
+}
+
+// Currently the cache token is only authorized for push and pull_request events
+// All other events will fail when reading and saving the cache
+// See GitHub Context https://help.github.com/actions/automating-your-workflow-with-github-actions/contexts-and-expression-syntax-for-github-actions#github-context
+export function isValidEvent(): boolean {
+    const githubEvent = process.env[Events.Key] || "";
+    return getSupportedEvents().includes(githubEvent);
+}