Implement action.

index.ts

@@ -1 +1,140 @@
-export {};
+import fs from 'fs';
+import path from 'path';
+import * as core from '@actions/core';
+import * as exec from '@actions/exec';
+import TOML from '@ltd/j-toml';
+
+interface Toolchain {
+	channel: string;
+	components: string[];
+	targets: string[];
+	profile: string;
+}
+
+interface ToolchainConfig {
+	toolchain: Partial<Toolchain>;
+}
+
+const DEFAULT_TOOLCHAIN: Toolchain = {
+	channel: 'stable',
+	components: [],
+	profile: 'minimal',
+	targets: [],
+};
+
+function parseConfig(configPath: string): Partial<Toolchain> {
+	const contents = fs.readFileSync(configPath, 'utf8').trim();
+
+	if (!contents.includes('[toolchain]')) {
+		core.debug('No [toolchain] section found, assuming legacy format');
+
+		return { channel: contents };
+	}
+
+	const config = TOML.parse(contents) as unknown as ToolchainConfig;
+
+	if (config.toolchain.channel) {
+		core.debug('Found channel in [toolchain] section');
+
+		return { channel: config.toolchain.channel };
+	}
+
+	core.debug('No channel found in [toolchain] section');
+
+	return {};
+}
+
+// https://rust-lang.github.io/rustup/overrides.html
+function detectToolchain(): Toolchain {
+	core.info('Detecting toolchain');
+
+	const toolchain = { ...DEFAULT_TOOLCHAIN };
+
+	if (process.env.RUSTUP_TOOLCHAIN) {
+		core.info('Using toolchain from RUSTUP_TOOLCHAIN environment variable');
+
+		Object.assign(toolchain, {
+			channel: process.env.RUSTUP_TOOLCHAIN,
+		});
+	} else {
+		core.info('Searching for rust-toolchain.toml or rust-toolchain file');
+
+		for (const configName of ['rust-toolchain.toml', 'rust-toolchain']) {
+			const configPath = path.join(process.cwd(), configName);
+
+			if (fs.existsSync(configPath)) {
+				core.debug(`Found ${configName}, parsing TOML`);
+
+				Object.assign(toolchain, parseConfig(configPath));
+				break;
+			}
+		}
+	}
+
+	core.info('Inheriting toolchain settings from inputs');
+
+	(Object.keys(DEFAULT_TOOLCHAIN) as (keyof typeof DEFAULT_TOOLCHAIN)[]).forEach((key) => {
+		const input = core.getInput(key);
+
+		if (input) {
+			core.debug(`Found input for ${key}: ${input}`);
+
+			if (key === 'components' || key === 'targets') {
+				input.split(',').forEach((part) => {
+					toolchain[key].push(part.trim());
+				});
+			} else {
+				toolchain[key] = input;
+			}
+		}
+	});
+
+	return toolchain;
+}
+
+async function installToolchain(toolchain: Toolchain) {
+	core.info('Installing toolchain with rustup');
+
+	const args = ['toolchain', 'install', toolchain.channel, '--profile', toolchain.profile];
+
+	toolchain.targets.forEach((target) => {
+		args.push('--target', target);
+	});
+
+	toolchain.components.forEach((component) => {
+		args.push('--component', component);
+	});
+
+	if (toolchain.channel === 'nightly' && toolchain.components.length > 0) {
+		args.push('--allow-downgrade');
+	}
+
+	args.push('--no-self-update');
+
+	await exec.exec('rustup', args);
+	await exec.exec('rustup', ['default', toolchain.channel]);
+
+	core.info('Logging installed toolchain versions');
+
+	await exec.exec('rustc', [`+${toolchain.channel}`, '--version', '--verbose']);
+}
+
+async function run() {
+	try {
+		await installToolchain(detectToolchain());
+	} catch (error: unknown) {
+		core.setFailed((error as Error).message);
+
+		throw error;
+	}
+
+	core.info('Setting cargo environment variables');
+
+	// Disable incremental compilation
+	core.exportVariable('CARGO_INCREMENTAL', '0');
+
+	// Always enable colored output
+	core.exportVariable('CARGO_TERM_COLOR', 'always');
+}
+
+void run();