Minor refactors in create-react-app (#8178)

- Remove templates version minimum stopgap.
- Replace indexOf with more idiomatic alternatives.
- Inline errorLogFilePatterns.
- Alphabetize validFiles.
- Simplify log file removal code.
- Move unconditional console.log() call outside of isSafe.
- Differentiate conflicting directories from files.
- Document yarn version special case.
- Inline printValidationResults.
- Standardize checkAppName output on failure.
- Add link for checkThatNpmCanReadCwd.

Functionally the code should be exactly the same.

packages/create-react-app/createReactApp.js

@@ -53,14 +53,6 @@ const validateProjectName = require('validate-npm-package-name');
 
 const packageJson = require('./package.json');
 
-// These files should be allowed to remain on a failed install,
-// but then silently removed during the next create.
-const errorLogFilePatterns = [
-  'npm-debug.log',
-  'yarn-error.log',
-  'yarn-debug.log',
-];
-
 let projectName;
 
 const program = new commander.Command(packageJson.name)
@@ -192,14 +184,6 @@ if (typeof projectName === 'undefined') {
   process.exit(1);
 }
 
-function printValidationResults(results) {
-  if (typeof results !== 'undefined') {
-    results.forEach(error => {
-      console.error(chalk.red(`  *  ${error}`));
-    });
-  }
-}
-
 createApp(
   projectName,
   program.verbose,
@@ -247,6 +231,7 @@ function createApp(
   if (!isSafeToCreateProjectIn(root, name)) {
     process.exit(1);
   }
+  console.log();
 
   console.log(`Creating a new React app in ${chalk.green(root)}.`);
   console.log();
@@ -448,10 +433,7 @@ function run(
       .then(({ isOnline, packageInfo, templateInfo }) => {
         let packageVersion = semver.coerce(packageInfo.version);
 
-        // This environment variable can be removed post-release.
-        const templatesVersionMinimum = process.env.CRA_INTERNAL_TEST
-          ? '3.2.0'
-          : '3.3.0';
+        const templatesVersionMinimum = '3.3.0';
 
         // Assume compatibility if we can't test the version.
         if (!semver.valid(packageVersion)) {
@@ -591,7 +573,7 @@ function getInstallPackage(version, originalDirectory) {
   if (validSemver) {
     packageToInstall += `@${validSemver}`;
   } else if (version) {
-    if (version[0] === '@' && version.indexOf('/') === -1) {
+    if (version[0] === '@' && !version.includes('/')) {
       packageToInstall += version;
     } else if (version.match(/^file:/)) {
       packageToInstall = `file:${path.resolve(
@@ -743,7 +725,7 @@ function getPackageInfo(installPackage) {
         );
         return Promise.resolve({ name: assumedProjectName });
       });
-  } else if (installPackage.indexOf('git+') === 0) {
+  } else if (installPackage.startsWith('git+')) {
     // Pull package name out of git urls e.g:
     // git+https://github.com/mycompany/react-scripts.git
     // git+ssh://github.com/mycompany/react-scripts.git#v1.2.3
@@ -785,17 +767,25 @@ function checkNpmVersion() {
 }
 
 function checkYarnVersion() {
+  const minYarnPnp = '1.12.0';
   let hasMinYarnPnp = false;
   let yarnVersion = null;
   try {
     yarnVersion = execSync('yarnpkg --version')
       .toString()
       .trim();
-    let trimmedYarnVersion = /^(.+?)[-+].+$/.exec(yarnVersion);
-    if (trimmedYarnVersion) {
-      trimmedYarnVersion = trimmedYarnVersion.pop();
+    if (semver.valid(yarnVersion)) {
+      hasMinYarnPnp = semver.gte(yarnVersion, minYarnPnp);
+    } else {
+      // Handle non-semver compliant yarn version strings, which yarn currently
+      // uses for nightly builds. The regex truncates anything after the first
+      // dash. See #5362.
+      const trimmedYarnVersionMatch = /^(.+?)[-+].+$/.exec(yarnVersion);
+      if (trimmedYarnVersionMatch) {
+        const trimmedYarnVersion = trimmedYarnVersionMatch.pop();
+        hasMinYarnPnp = semver.gte(trimmedYarnVersion, minYarnPnp);
+      }
     }
-    hasMinYarnPnp = semver.gte(trimmedYarnVersion || yarnVersion, '1.12.0');
   } catch (err) {
     // ignore
   }
@@ -840,22 +830,29 @@ function checkAppName(appName) {
   const validationResult = validateProjectName(appName);
   if (!validationResult.validForNewPackages) {
     console.error(
-      `Could not create a project called ${chalk.red(
-        `"${appName}"`
-      )} because of npm naming restrictions:`
+      chalk.red(
+        `Cannot create a project named ${chalk.green(
+          `"${appName}"`
+        )} because of npm naming restrictions:\n`
+      )
     );
-    printValidationResults(validationResult.errors);
-    printValidationResults(validationResult.warnings);
+    [
+      ...(validationResult.errors || []),
+      ...(validationResult.warnings || []),
+    ].forEach(error => {
+      console.error(chalk.red(`  * ${error}`));
+    });
+    console.error(chalk.red('\nPlease choose a different project name.'));
     process.exit(1);
   }
 
   // TODO: there should be a single place that holds the dependencies
   const dependencies = ['react', 'react-dom', 'react-scripts'].sort();
-  if (dependencies.indexOf(appName) >= 0) {
+  if (dependencies.includes(appName)) {
     console.error(
       chalk.red(
-        `We cannot create a project called ${chalk.green(
-          appName
+        `Cannot create a project named ${chalk.green(
+          `"${appName}"`
         )} because a dependency with the same name exists.\n` +
           `Due to the way npm works, the following names are not allowed:\n\n`
       ) +
@@ -917,41 +914,57 @@ function setCaretRangeForRuntimeDeps(packageName) {
 function isSafeToCreateProjectIn(root, name) {
   const validFiles = [
     '.DS_Store',
-    'Thumbs.db',
     '.git',
+    '.gitattributes',
     '.gitignore',
-    '.idea',
-    'README.md',
-    'LICENSE',
+    '.gitlab-ci.yml',
     '.hg',
-    '.hgignore',
     '.hgcheck',
+    '.hgignore',
+    '.idea',
     '.npmignore',
-    'mkdocs.yml',
-    'docs',
     '.travis.yml',
-    '.gitlab-ci.yml',
-    '.gitattributes',
+    'docs',
+    'LICENSE',
+    'README.md',
+    'mkdocs.yml',
+    'Thumbs.db',
   ];
-  console.log();
+  // These files should be allowed to remain on a failed install, but then
+  // silently removed during the next create.
+  const errorLogFilePatterns = [
+    'npm-debug.log',
+    'yarn-error.log',
+    'yarn-debug.log',
+  ];
+  const isErrorLog = file => {
+    return errorLogFilePatterns.some(pattern => file.startsWith(pattern));
+  };
 
   const conflicts = fs
     .readdirSync(root)
     .filter(file => !validFiles.includes(file))
     // IntelliJ IDEA creates module files before CRA is launched
     .filter(file => !/\.iml$/.test(file))
     // Don't treat log files from previous installation as conflicts
-    .filter(
-      file => !errorLogFilePatterns.some(pattern => file.indexOf(pattern) === 0)
-    );
+    .filter(file => !isErrorLog(file));
 
   if (conflicts.length > 0) {
     console.log(
       `The directory ${chalk.green(name)} contains files that could conflict:`
     );
     console.log();
     for (const file of conflicts) {
-      console.log(`  ${file}`);
+      try {
+        const stats = fs.lstatSync(path.join(root, file));
+        if (stats.isDirectory()) {
+          console.log(`  ${chalk.blue(`${file}/`)}`);
+        } else {
+          console.log(`  ${file}`);
+        }
+      } catch (e) {
+        console.log(`  ${file}`);
+      }
     }
     console.log();
     console.log(
@@ -961,15 +974,11 @@ function isSafeToCreateProjectIn(root, name) {
     return false;
   }
 
-  // Remove any remnant files from a previous installation
-  const currentFiles = fs.readdirSync(path.join(root));
-  currentFiles.forEach(file => {
-    errorLogFilePatterns.forEach(errorLogFilePattern => {
-      // This will catch `(npm-debug|yarn-error|yarn-debug).log*` files
-      if (file.indexOf(errorLogFilePattern) === 0) {
-        fs.removeSync(path.join(root, file));
-      }
-    });
+  // Remove any log files from a previous installation.
+  fs.readdirSync(root).forEach(file => {
+    if (isErrorLog(file)) {
+      fs.removeSync(path.join(root, file));
+    }
   });
   return true;
 }
@@ -989,6 +998,8 @@ function getProxy() {
     }
   }
 }
+
+// See https://github.com/facebook/create-react-app/pull/3355
 function checkThatNpmCanReadCwd() {
   const cwd = process.cwd();
   let childOutput = null;
@@ -1013,7 +1024,7 @@ function checkThatNpmCanReadCwd() {
   // "; cwd = C:\path\to\current\dir" (unquoted)
   // I couldn't find an easier way to get it.
   const prefix = '; cwd = ';
-  const line = lines.find(line => line.indexOf(prefix) === 0);
+  const line = lines.find(line => line.startsWith(prefix));
   if (typeof line !== 'string') {
     // Fail gracefully. They could remove it.
     return true;