Fail action execution on unhandled errors

Without this, the error logs contain an "UnhandledPromiseRejectionError"
but the action is reported as succeeding.

.github/workflows/failure-cases.yml

@@ -11,26 +11,27 @@ env:
   CACHE_KEY_PREFIX: ${{github.workflow}}#${{github.run_number}}-
 
 jobs:
+
   wrapper-missing:
+    continue-on-error: true
     runs-on: ubuntu-latest
     steps:
     - name: Checkout sources
       uses: actions/checkout@v2
     - name: Test wrapper missing
       uses: ./
-      continue-on-error: true
       with:
         build-root-directory: __tests__/samples/no-wrapper
         arguments: help
 
   bad-configuration:
+    continue-on-error: true
     runs-on: ubuntu-latest
     steps:
     - name: Checkout sources
       uses: actions/checkout@v2
     - name: Test bad config value
       uses: ./
-      continue-on-error: true
       with:
         build-root-directory: __tests__/samples/no-wrapper
         arguments: help

src/main.ts

@@ -9,12 +9,12 @@ import * as provision from './provision'
 
 // Invoked by GitHub Actions
 export async function run(): Promise<void> {
+    try {
         const workspaceDirectory = process.env[`GITHUB_WORKSPACE`] || ''
         const buildRootDirectory = resolveBuildRootDirectory(workspaceDirectory)
 
         await caches.restore(buildRootDirectory)
 
-    try {
         const args: string[] = parseCommandLineArguments()
         // TODO: instead of running with no-daemon, run `--stop` in post action.
         args.push('--no-daemon')
@@ -39,10 +39,10 @@ export async function run(): Promise<void> {
             core.setFailed(`Gradle process exited with status ${result.status}`)
         }
     } catch (error) {
-        if (!(error instanceof Error)) {
-            throw error
+        core.setFailed(String(error))
+        if (error instanceof Error && error.stack) {
+            core.info(error.stack)
         }
-        core.setFailed(error.message)
     }
 }
 

src/post.ts

@@ -1,8 +1,16 @@
+import * as core from '@actions/core'
 import * as caches from './caches'
 
 // Invoked by GitHub Actions
 export async function run(): Promise<void> {
+    try {
         await caches.save()
+    } catch (error) {
+        core.setFailed(String(error))
+        if (error instanceof Error && error.stack) {
+            core.info(error.stack)
+        }
+    }
 }
 
 run()