Expose ghcup binary location

README.md

@@ -200,7 +200,7 @@ jobs:
 | `stack-setup-ghc`       | If set, `enable-stack` must be set. Runs stack setup to install the specified GHC. (Note: setting this does _not_ imply `stack-no-global`.) | "boolean" | false/unset |
 | `disable-matcher`       | If set, disables match messages from GHC as GitHub CI annotations.                                                                          | "boolean" | false/unset |
 | `cabal-update`          | If set to `false`, skip `cabal update` step.                                                                                                | `boolean` | `true`      |
-| `ghcup-release-channel` | If set, add a [release channel](https://www.haskell.org/ghcup/guide/#metadata) to ghcup.                                        | `URL`     | none        |
+| `ghcup-release-channel` | If set, add a [release channel](https://www.haskell.org/ghcup/guide/#metadata) to ghcup.                                                    | `URL`     | none        |
 
 Note: "boolean" types are set/unset, not true/false.
 That is, setting any "boolean" to a value other than the empty string (`""`) will be considered true/set.
@@ -228,6 +228,7 @@ and `ghc-exe` and `ghc-path` will be set accordingly.
 | `stack-path`    | The path of the `stack` executable _directory_                                                                             | string |
 | `cabal-store`   | The path to the cabal store                                                                                                | string |
 | `stack-root`    | The path to the stack root (equal to the `STACK_ROOT` environment variable if it is set; otherwise an OS-specific default) | string |
+| `ghcup-command` | The path of the `ghcup` _executable_. Might not be an absolute file path.                                                  | string |
 
 ## Version Support
 

action.yml

@@ -45,6 +45,8 @@ outputs:
     description: 'The resolved version of stack'
   ghc-exe:
     description: 'The path of the ghc _executable_'
+  ghcup-command:
+    description: 'The path of the ghcup _executable_'
   cabal-exe:
     description: 'The path of the cabal _executable_'
   stack-exe:

src/installer.ts

@@ -18,6 +18,11 @@ function failed(tool: Tool, version: string): void {
   throw new Error(`All install methods for ${tool} ${version} failed`);
 }
 
+export async function configureGhcupOutput(os: OS, arch: Arch): Promise<void> {
+  const bin = await ghcupBin(os, arch);
+  core.setOutput('ghcup-command', bin);
+}
+
 async function configureOutputs(
   tool: Tool,
   version: string,

src/setup-haskell.ts

@@ -5,7 +5,12 @@ import * as fs from 'fs';
 import * as path from 'path';
 import {EOL} from 'os';
 import {getOpts, getDefaults, Tool} from './opts';
-import {addGhcupReleaseChannel, installTool, resetTool} from './installer';
+import {
+  addGhcupReleaseChannel,
+  configureGhcupOutput,
+  installTool,
+  resetTool
+} from './installer';
 import type {Arch, OS} from './opts';
 import {exec} from '@actions/exec';
 
@@ -40,6 +45,8 @@ export default async function run(
     core.debug(`run: os     = ${JSON.stringify(os)}`);
     core.debug(`run: opts   = ${JSON.stringify(opts)}`);
 
+    await configureGhcupOutput(os, arch);
+
     if (opts.ghcup.releaseChannel) {
       await core.group(`Preparing ghcup environment`, async () =>
         addGhcupReleaseChannel(opts.ghcup.releaseChannel!, os, arch)