Support functional engine

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- Support functional engine ([#42](https://github.com/marp-team/marp-cli/pull/42))
+
 ## v0.0.14 - 2018-11-24
 
 ### Security

src/converter.ts

@@ -167,7 +167,12 @@ export class Converter {
     // for marp-core
     if (html !== undefined) opts.html = html
 
-    const engine = new this.options.engine(opts)
+    const { prototype } = this.options.engine
+
+    const engine =
+      prototype && prototype.hasOwnProperty('constructor')
+        ? new this.options.engine(opts)
+        : (<any>this.options.engine)(opts)
 
     if (typeof engine.render !== 'function')
       error('Specified engine has not implemented render() method.')

test/_configs/custom-engine/anonymous.js

@@ -0,0 +1,6 @@
+const { Marpit } = require('@marp-team/marpit')
+
+module.exports = {
+  engine: jest.fn(opts => new Marpit(opts)),
+  options: { customOption: true },
+}

test/marp-cli.ts

@@ -454,7 +454,7 @@ describe('Marp CLI', () => {
           expect(html).toContain('@theme a')
         })
 
-        it('allows custom engine specified in js config', async () => {
+        it('allows custom engine class specified in js config', async () => {
           const stdout = jest
             .spyOn(process.stdout, 'write')
             .mockImplementation()
@@ -470,6 +470,20 @@ describe('Marp CLI', () => {
           expect(html).toContain('<b>custom</b>')
           expect(html).toContain('/* custom */')
         })
+
+        it('allows custom engine function specified in js config', async () => {
+          jest.spyOn(process.stdout, 'write').mockImplementation()
+          jest.spyOn(console, 'warn').mockImplementation()
+
+          const conf = assetFn('_configs/custom-engine/anonymous.js')
+          const md = assetFn('_configs/custom-engine/md.md')
+          const { engine } = require(conf)
+
+          expect(await marpCli(['-c', conf, md, '-o', '-'])).toBe(0)
+          expect(engine).toBeCalledWith(
+            expect.objectContaining({ customOption: true })
+          )
+        })
       })
     })
   })