Add Yarn PnP support

src/linters/eslint.js

@@ -1,6 +1,6 @@
 const commandExists = require("../../vendor/command-exists");
-const { run } = require("../utils/action");
 const { initLintResult } = require("../utils/lint-result");
+const { runNpmBin } = require("../utils/npm");
 const { removeTrailingPeriod } = require("../utils/string");
 
 /**
@@ -23,7 +23,7 @@ class ESLint {
 
 		// Verify that ESLint is installed
 		try {
-			run("npx --no-install eslint -v", { dir });
+			runNpmBin("eslint -v", { dir });
 		} catch (err) {
 			throw new Error(`${this.name} is not installed`);
 		}
@@ -40,8 +40,8 @@ class ESLint {
 	static lint(dir, extensions, args = "", fix = false) {
 		const extensionsArg = extensions.map(ext => `.${ext}`).join(",");
 		const fixArg = fix ? "--fix" : "";
-		return run(
-			`npx --no-install eslint --ext ${extensionsArg} ${fixArg} --no-color --format json ${args} "."`,
+		return runNpmBin(
+			`eslint --ext ${extensionsArg} ${fixArg} --no-color --format json ${args} "."`,
 			{
 				dir,
 				ignoreErrors: true,

src/linters/prettier.js

@@ -1,6 +1,6 @@
 const commandExists = require("../../vendor/command-exists");
-const { run } = require("../utils/action");
 const { initLintResult } = require("../utils/lint-result");
+const { runNpmBin } = require("../utils/npm");
 
 /**
  * https://prettier.io
@@ -22,7 +22,7 @@ class Prettier {
 
 		// Verify that Prettier is installed
 		try {
-			run("npx --no-install prettier -v", { dir });
+			runNpmBin("prettier -v", { dir });
 		} catch (err) {
 			throw new Error(`${this.name} is not installed`);
 		}
@@ -40,7 +40,7 @@ class Prettier {
 		const files =
 			extensions.length === 1 ? `**/*.${extensions[0]}` : `**/*.{${extensions.join(",")}}`;
 		const fixArg = fix ? "--write" : "--list-different";
-		return run(`npx --no-install prettier ${fixArg} --no-color ${args} "${files}"`, {
+		return runNpmBin(`prettier ${fixArg} --no-color ${args} "${files}"`, {
 			dir,
 			ignoreErrors: true,
 		});

src/linters/stylelint.js

@@ -1,6 +1,6 @@
 const commandExists = require("../../vendor/command-exists");
-const { run } = require("../utils/action");
 const { initLintResult } = require("../utils/lint-result");
+const { runNpmBin } = require("../utils/npm");
 
 /**
  * https://stylelint.io
@@ -22,7 +22,7 @@ class Stylelint {
 
 		// Verify that stylelint is installed
 		try {
-			run("npx --no-install stylelint -v", { dir });
+			runNpmBin("stylelint -v", { dir });
 		} catch (err) {
 			throw new Error(`${this.name} is not installed`);
 		}
@@ -40,13 +40,10 @@ class Stylelint {
 		const files =
 			extensions.length === 1 ? `**/*.${extensions[0]}` : `**/*.{${extensions.join(",")}}`;
 		const fixArg = fix ? "--fix" : "";
-		return run(
-			`npx --no-install stylelint --no-color --formatter json ${fixArg} ${args} "${files}"`,
-			{
-				dir,
-				ignoreErrors: true,
-			},
-		);
+		return runNpmBin(`stylelint --no-color --formatter json ${fixArg} ${args} "${files}"`, {
+			dir,
+			ignoreErrors: true,
+		});
 	}
 
 	/**

src/utils/npm.js

@@ -0,0 +1,33 @@
+const { existsSync } = require("fs");
+const { join } = require("path");
+
+const { run } = require("../utils/action");
+
+const YARN_LOCK_NAME = "yarn.lock";
+
+/**
+ * Determines whether Yarn should be used to execute commands or binaries. This decision is based on
+ * the existence of a Yarn lockfile in the package directory. The distinction between NPM and Yarn
+ * is necessary e.g. for Yarn Plug'n'Play to work
+ * @param {string} [pkgRoot] - Package directory (directory where Yarn lockfile would exist)
+ * @returns {boolean} - Whether Yarn should be used
+ */
+function useYarn(pkgRoot) {
+	// Use an absolute path if `pkgRoot` is specified and a relative one (current directory) otherwise
+	const lockfilePath = pkgRoot ? join(pkgRoot, YARN_LOCK_NAME) : YARN_LOCK_NAME;
+	return existsSync(lockfilePath);
+}
+
+/**
+ * Executes the specified binary with NPM or Yarn (the correct tool is determined automatically).
+ * This function wraps the general {@see run} function and accepts the same parameters
+ * @param {string} cmd - NPM binary to execute
+ * @param {{dir: string, ignoreErrors: boolean}} [options] - {@see RUN_OPTIONS_DEFAULTS}
+ * @returns {{status: number, stdout: string, stderr: string}} - Output of the NPM binary
+ */
+function runNpmBin(cmd, options) {
+	const npmCmd = useYarn(options.dir) ? `yarn run --silent ${cmd}` : `npx --no-install ${cmd}`;
+	return run(npmCmd, options);
+}
+
+module.exports = { runNpmBin };