PatternLab only loads the pattern engines from the config

Author: ringods

packages/core/src/lib/findModules.js

@@ -1,58 +1,11 @@
 // special shoutout to Geoffrey Pursell for single-handedly making Pattern Lab Node Pattern Engines possible! aww thanks :)
 'use strict';
-const { existsSync } = require('fs');
 const path = require('path');
 
-const findModules = require('./findModules');
-
-const engineMatcher = /^engine-(.*)$/;
-
 const logger = require('./log');
 
-const enginesDirectories = [
-  {
-    displayName: 'the core',
-    path: path.resolve(__dirname, '..', '..', 'node_modules'),
-  },
-  {
-    displayName: 'the edition or test directory',
-    path: path.join(process.cwd(), 'node_modules'),
-  },
-];
-
-/**
- * Given a path: return the engine name if the path points to a valid engine
- * module directory, or false if it doesn't.
- * @param filePath
- * @returns Engine name if exists or FALSE
- */
-function isEngineModule(filePath) {
-  const baseName = path.basename(filePath);
-  const engineMatch = baseName.match(engineMatcher);
-
-  if (engineMatch) {
-    return engineMatch[1];
-  }
-  return false;
-}
-
-/**
- * @name resolveEngines
- * @desc Creates an array of all available patternlab engines
- * @param {string} dir - The directory to search for engines and scoped engines)
- * @return {Array<Engine>} An array of engine objects
- */
-function resolveEngines(dir) {
-  // Guard against non-existent directories.
-  if (!existsSync(dir)) {
-    return []; // Silence is golden …
-  }
-
-  return findModules(dir, isEngineModule);
-}
-
-function findEngineModulesInDirectory(dir) {
-  const foundEngines = resolveEngines(dir);
+function findEnginesInConfig(config) {
+  const foundEngines = config.engines;
   return foundEngines;
 }
 
@@ -80,49 +33,43 @@ const PatternEngines = Object.create({
   loadAllEngines: function(patternLabConfig) {
     const self = this;
 
-    // Try to load engines! We scan for engines at each path specified above. This
-    // function is kind of a big deal.
-    enginesDirectories.forEach(function(engineDirectory) {
-      const enginesInThisDir = findEngineModulesInDirectory(
-        engineDirectory.path
-      );
-
-      logger.debug(`Loading engines from ${engineDirectory.displayName}...`);
-
-      // find all engine-named things in this directory and try to load them,
-      // unless it's already been loaded.
-      enginesInThisDir.forEach(function(engineDiscovery) {
-        let errorMessage;
-        const successMessage = 'good to go';
-
-        try {
-          // Give it a try! load 'er up. But not if we already have,
-          // of course.  Also pass the pattern lab config object into
-          // the engine's closure scope so it can know things about
-          // things.
-          if (self[engineDiscovery.name]) {
-            throw new Error('already loaded, skipping.');
-          }
-          self[engineDiscovery.name] = require(engineDiscovery.modulePath);
-          if (
-            typeof self[engineDiscovery.name].usePatternLabConfig === 'function'
-          ) {
-            self[engineDiscovery.name].usePatternLabConfig(patternLabConfig);
-          }
-          if (typeof self[engineDiscovery.name].spawnMeta === 'function') {
-            self[engineDiscovery.name].spawnMeta(patternLabConfig);
-          }
-        } catch (err) {
-          errorMessage = err.message;
-        } finally {
-          // report on the status of the engine, one way or another!
-          logger.info(
-            `Pattern Engine ${engineDiscovery.name}: ${
-              errorMessage ? errorMessage : successMessage
-            }`
-          );
+    // Try to load engines! We load the engines configured in patternlab-config.json
+    const enginesInConfig = findEnginesInConfig(patternLabConfig);
+
+    logger.debug('Loading engines from patternlab-config.json');
+
+    // Try loading each of the configured pattern engines
+    enginesInConfig.forEach(function(engineConfig) {
+      let errorMessage;
+      const successMessage = 'good to go';
+
+      try {
+        // Give it a try! load 'er up. But not if we already have,
+        // of course.  Also pass the pattern lab config object into
+        // the engine's closure scope so it can know things about
+        // things.
+        if (self[engineConfig.extension]) {
+          throw new Error('already loaded, skipping.');
+        }
+        self[engineConfig.extension] = require(engineConfig.package);
+        if (
+          typeof self[engineConfig.extension].usePatternLabConfig === 'function'
+        ) {
+          self[engineConfig.extension].usePatternLabConfig(patternLabConfig);
         }
-      });
+        if (typeof self[engineConfig.extension].spawnMeta === 'function') {
+          self[engineConfig.extension].spawnMeta(patternLabConfig);
+        }
+      } catch (err) {
+        errorMessage = err.message;
+      } finally {
+        // report on the status of the engine, one way or another!
+        logger.info(
+          `Pattern Engine ${engineConfig.extension}: ${
+            errorMessage ? errorMessage : successMessage
+          }`
+        );
+      }
     });
 
     // Complain if for some reason we haven't loaded any engines.

packages/core/src/lib/pattern_engines.js

@@ -108,7 +108,7 @@ const starterkit_manager = function(config) {
    *
    * @return {array} List of starter kits installed
    */
-  //TODO review for deletion or convert callers to use findModules()
+  //TODO review for deletion
   function detectStarterKits() {
     const node_modules_path = path.join(process.cwd(), 'node_modules');
     const npm_modules = fs.readdirSync(node_modules_path).filter(function(dir) {

packages/core/src/lib/starterkit_manager.js

@@ -73,6 +73,16 @@
     "density": "compact",
     "layout": "horizontal"
   },
+  "engines": [
+    {
+      "package": "@pattern-lab/engine-mustache",
+      "extension": "mustache"
+    },
+    {
+      "package": "@pattern-lab/engine-handlebars",
+      "extension": "hbs"
+    }
+  ],
   "uikits": [
     {
       "name": "uikit-workshop",