Add output ghc-version

action.yml

@@ -3,6 +3,11 @@ author: Simon Hengel
 inputs:
   ghc-version:
     required: true
+
+outputs:
+  ghc-version:
+    description: 'The installed GHC version.'
+
 runs:
   using: node16
   main: dist/index.js

src/main.ts

@@ -12,12 +12,8 @@ async function main() {
       core.addPath(home + '/.cabal/bin/');
     }
     const requested = core.getInput('ghc-version');
-    if (requested === 'system') {
-      report();
-    } else {
-      const version = await install(requested);
-      await verify(version);
-    }
+    const version = await ensure(requested);
+    core.setOutput('ghc-version', version);
   } catch (error) {
     if (error instanceof Error) {
       core.setFailed(error.message);
@@ -27,6 +23,18 @@ async function main() {
   }
 }
 
+async function ensure(requested: string): Promise<string> {
+  if (requested === 'system') {
+    const version = installed();
+    core.info(`Using GHC version ${version}.`);
+    return version;
+  } else {
+    const version = await install(requested);
+    await verify(version);
+    return version;
+  }
+}
+
 async function install(requested: string): Promise<string> {
   const resolved = await resolve(requested);
   switch (resolved.source) {
@@ -48,10 +56,6 @@ async function verify(expected: string) {
   core.info(`Installed GHC version ${expected}.`);
 }
 
-async function report() {
-  core.info(`Using GHC version ${await installed()}.`);
-}
-
 async function installed(): Promise<string> {
   const result = await getExecOutput('ghc', ['--numeric-version'], {
     silent: true,