Support template-only imports

packages/addon-dev/src/rollup-hbs-plugin.ts

@@ -1,23 +1,90 @@
 import { createFilter } from '@rollup/pluginutils';
-import type { Plugin } from 'rollup';
+import { pathExists } from 'fs-extra';
 import { readFileSync } from 'fs';
+import path from 'path';
+
+import type { Plugin } from 'rollup';
+
 const backtick = '`';
 
 export default function rollupHbsPlugin(): Plugin {
   const filter = createFilter('**/*.hbs');
 
   return {
     name: 'rollup-hbs-plugin',
-    load(id: string) {
+    async load(id: string) {
       if (!filter(id)) return;
-      let input = readFileSync(id, 'utf8');
-      let code =
-        `import { hbs } from 'ember-cli-htmlbars';\n` +
-        `export default hbs${backtick}${input}${backtick};`;
+
+      if (await isTemplateOnly(id)) {
+        return { code: getTemplateOnly(id), id };
+      }
+
+      // For templates with a backing class
       return {
-        code,
+        code: getTemplateFactory(id),
         id: id + '.js',
       };
     },
+
+    // template-only components may be imported
+    async resolveId(source, importer, options) {
+      let resolution = await this.resolve(source, importer, {
+        ...options,
+        skipSelf: true,
+      });
+
+      let ext = path.extname(source);
+
+      // For hbs files, we _might_ have a template-only situation
+      if (resolution && ext !== '.hbs') return resolution;
+      if (!importer) return null;
+
+      // source may or may not have '.hbs' on the path
+      let dir = path.dirname(importer);
+      let nameWithExt = ext ? source : source + '.hbs';
+      let maybeHbs = path.join(dir, nameWithExt);
+
+      resolution = await this.resolve(maybeHbs, importer, {
+        ...options,
+        skipSelf: true,
+      });
+
+      if (resolution) return resolution;
+
+      return null;
+    },
   };
 }
+
+async function isTemplateOnly(hbsPath: string) {
+  let jsPath = hbsPath.replace(/\.hbs$/, '.js');
+  let tsPath = hbsPath.replace(/\.hbs$/, '.ts');
+
+  let hasJs = await pathExists(jsPath);
+  let hasTs = await pathExists(tsPath);
+
+  let hasClass = hasJs || hasTs;
+
+  return !hasClass;
+}
+
+function getTemplateOnly(hbsPath: string) {
+  let input = readFileSync(hbsPath, 'utf8');
+  let code =
+    `import { hbs } from 'ember-cli-htmlbars';\n` +
+    `import templateOnly from '@ember/component/template-only';\n` +
+    `import { setComponentTemplate } from '@ember/component';\n` +
+    `export default setComponentTemplate(\n` +
+    `hbs${backtick}${input.trim()}${backtick}, templateOnly());`;
+
+  return code;
+}
+
+function getTemplateFactory(hbsPath: string) {
+  let input = readFileSync(hbsPath, 'utf8');
+  let code =
+    `import { hbs } from 'ember-cli-htmlbars';\n` +
+    `export default hbs${backtick}${input.trim()}${backtick};`;
+
+  return code;
+}

packages/addon-dev/src/rollup-public-entrypoints.ts

@@ -1,9 +1,10 @@
 import walkSync from 'walk-sync';
-import type { Plugin } from 'rollup';
 import { join } from 'path';
 
+import type { Plugin } from 'rollup';
+
 function normalizeFileExt(fileName: string) {
-  return fileName.replace(/\.ts|\.gts|\.gjs$/, '.js');
+  return fileName.replace(/\.ts|\.hbs|\.gts|\.gjs$/, '.js');
 }
 
 export default function publicEntrypoints(args: {
@@ -12,10 +13,12 @@ export default function publicEntrypoints(args: {
 }): Plugin {
   return {
     name: 'addon-modules',
-    buildStart() {
-      for (let name of walkSync(args.srcDir, {
-        globs: args.include,
-      })) {
+    async buildStart() {
+      let matches = walkSync(args.srcDir, {
+        globs: [...args.include],
+      });
+
+      for (let name of matches) {
         this.emitFile({
           type: 'chunk',
           id: join(args.srcDir, name),