Add devDependencies support for templates

Summary:
Add devDependencies support to React Native templates.
Template can have a devDependencies.json file with devDependencies inside.
Using separate files to dependencies and devDependencies, it maintains compatibility with the current version.

Allows React Native templates to have devDependencies, which can help applications to have better organization, quality and testability. It's possible start a new app with some dependencies for dev support like prettier, reactotron, eslint packages and others.

Add a devDependencies.json file with at least one dependency (like prettier)

[CLI] [FEATURE] [local-cli/generator/templates.js] - Add support to devDependencies for react native templates
Closes #18164

Differential Revision: D7660744

Pulled By: hramos

fbshipit-source-id: 6fbb13832d2d1bd0c06bada0842c890dd99cf331

local-cli/generator/templates.js

@@ -99,6 +99,7 @@ function createFromBuiltInTemplate(templateName, destPath, newProjectName, yarnV
     newProjectName,
   );
   installTemplateDependencies(templatePath, yarnVersion);
+  installTemplateDevDependencies(templatePath, yarnVersion);
 }
 
 /**
@@ -143,6 +144,7 @@ function createFromRemoteTemplate(template, destPath, newProjectName, yarnVersio
       }
     );
     installTemplateDependencies(templatePath, yarnVersion);
+    installTemplateDevDependencies(templatePath, yarnVersion);
   } finally {
     // Clean up the temp files
     try {
@@ -196,6 +198,38 @@ function installTemplateDependencies(templatePath, yarnVersion) {
   execSync('react-native link', {stdio: 'inherit'});
 }
 
+function installTemplateDevDependencies(templatePath, yarnVersion) {
+  // devDependencies.json is a special file that lists additional develop dependencies
+  // that are required by this template
+  const devDependenciesJsonPath = path.resolve(
+    templatePath, 'devDependencies.json'
+  );
+  console.log('Adding develop dependencies for the project...');
+  if (!fs.existsSync(devDependenciesJsonPath)) {
+    console.log('No additional develop dependencies.');
+    return;
+  }
+
+  let dependencies;
+  try {
+    dependencies = JSON.parse(fs.readFileSync(devDependenciesJsonPath));
+  } catch (err) {
+    throw new Error(
+      'Could not parse the template\'s devDependencies.json: ' + err.message
+    );
+  }
+  for (let depName in dependencies) {
+    const depVersion = dependencies[depName];
+    const depToInstall = depName + '@' + depVersion;
+    console.log('Adding ' + depToInstall + '...');
+    if (yarnVersion) {
+      execSync(`yarn add ${depToInstall} -D`, {stdio: 'inherit'});
+    } else {
+      execSync(`npm install ${depToInstall} --save-dev --save-exact`, {stdio: 'inherit'});
+    }
+  }
+}
+
 module.exports = {
   listTemplatesAndExit,
   createProjectFromTemplate,