Output rustc, cargo and rustup versions as Action outputs (#47)

README.md

@@ -48,6 +48,20 @@ See [additional recipes here](https://github.com/actions-rs/meta).
 | `profile`    |          | Execute `rustup set profile {value}` before installing the toolchain, ex. `minimal`                                                                 | string |         |
 | `components` |          | Comma-separated list of the additional components to install, ex. `clippy, rustfmt`                                                                 | string |         |
 
+## Outputs
+
+Installed `rustc`, `cargo` and `rustup` versions can be fetched from the Action outputs:
+
+| Name         | Description           | Example                         |
+| ------------ | --------------------- | ------------------------------- |
+| `rustc`      | Rustc version         | `1.40.0 (73528e339 2019-12-16)` |
+| `rustc-hash` | Rustc version hash    | `73528e339`                     |
+| `cargo`      | Cargo version         | `1.40.0 (bc8e4c8be 2019-11-22)` |
+| `rustup`     | rustup version        | `1.21.1 (7832b2ebe 2019-12-20)` |
+
+Note: `rustc-hash` output value can be used with [actions/cache](https://github.com/actions/cache) Action
+to store cache for different Rust versions, as it is unique across different Rust versions and builds (including `nightly`).
+
 ## Profiles
 
 This Action supports rustup [profiles](https://blog.rust-lang.org/2019/10/15/Rustup-1.20.0.html#profiles),

src/main.ts

@@ -4,6 +4,7 @@ import * as io from '@actions/io';
 import path from "path";
 
 import * as args from './args';
+import * as versions from './versions';
 import {RustUp, ToolchainOptions} from '@actions-rs/core';
 
 async function run() {
@@ -52,6 +53,8 @@ async function run() {
     if (opts.target) {
         await rustup.addTarget(opts.target, opts.name);
     }
+
+    await versions.gatherInstalledVersions();
 }
 
 async function main() {

src/versions.ts

@@ -0,0 +1,77 @@
+import * as exec from '@actions/exec';
+import * as core from '@actions/core';
+
+export async function gatherInstalledVersions(): Promise<void> {
+    try {
+        core.startGroup('Gathering installed versions');
+
+        await rustc();
+        await cargo();
+        await rustup();
+    } finally {
+        core.endGroup();
+    }
+}
+
+/**
+ * Fetch currently used `rustc` version
+ */
+async function rustc(): Promise<void> {
+    const stdout = await getStdout('rustc', ['-V']);
+    const version = parse(stdout);
+
+    core.setOutput('rustc', version.long);
+    core.setOutput('rustc-hash', version.hash);
+}
+
+/**
+ * Fetch currently used `cargo` version
+ */
+async function cargo(): Promise<void> {
+    const stdout = await getStdout('cargo', ['-V']);
+    const version = parse(stdout);
+
+    core.setOutput('cargo', version.long);
+//     core.setOutput('cargo_short', version.short);
+}
+
+async function rustup(): Promise<void> {
+    const stdout = await getStdout('rustup', ['-V']);
+    const version = parse(stdout);
+
+    core.setOutput('rustup', version.long);
+//     core.setOutput('rustup_short', version.short);
+}
+
+interface Version {
+    long: string,
+    hash: string,
+}
+
+function parse(stdout: string): Version {
+    stdout = stdout.trim();
+    const matches = stdout.match(/\S+\s((\S+)\s\((\S+)\s(\S+)\))/m);
+    if (matches == null) {
+        throw new Error(`Unable to parse version from the "${stdout}" string`);
+    }
+
+    return {
+        long: matches[1],
+        hash: matches[3],
+    }
+}
+
+async function getStdout(exe: string, args: string[], options?: {}): Promise<string> {
+    let stdout = '';
+    const resOptions = Object.assign({}, options, {
+        listeners: {
+            stdout: (buffer: Buffer) => {
+                stdout += buffer.toString();
+            },
+        },
+    });
+
+    await exec.exec(exe, args, resOptions);
+
+    return stdout;
+}