feat: stream rendering, closed #361 fixes #360

src/render/emitter.ts

@@ -1,29 +1,15 @@
-import { stringify, toValue } from '../util/underscore'
-
-export class Emitter {
-  public html: any = '';
-  public break = false;
-  public continue = false;
-  private keepOutputType? = false;
-
-  constructor (keepOutputType: boolean|undefined) {
-    this.keepOutputType = keepOutputType
-  }
-
-  public write (html: any) {
-    if (this.keepOutputType === true) {
-      html = toValue(html)
-    } else {
-      html = stringify(html)
-    }
-    // This will only preserve the type if the value is isolated.
-    // I.E:
-    // {{ my-port }} -> 42
-    // {{ my-host }}:{{ my-port }} -> 'host:42'
-    if (this.keepOutputType === true && typeof html !== 'string' && this.html === '') {
-      this.html = html
-    } else {
-      this.html = stringify(this.html) + stringify(html)
-    }
-  }
+export interface Emitter {
+  /**
+   * Write a html value into emitter
+   * @param html string, Drop or other primitive value
+   */
+  write (html: any): void;
+  /**
+   * Notify the emitter render has ended
+   */
+  end (): void;
+  /**
+   * Collect rendered string value immediately
+   */
+  collect (): string;
 }

src/render/render.ts

@@ -1,23 +1,34 @@
 import { RenderError } from '../util/error'
 import { Context } from '../context/context'
 import { Template } from '../template/template'
-import { Emitter } from './emitter'
+import { Emitter } from '../emitters/emitter'
+import { SimpleEmitter } from '../emitters/simple-emitter'
+import { StreamedEmitter } from '../emitters/streamed-emitter'
+import { toThenable } from '../util/async'
+import { KeepingTypeEmitter } from '../emitters/keeping-type-emitter'
 
 export class Render {
+  public renderTemplatesToNodeStream (templates: Template[], ctx: Context): NodeJS.ReadableStream {
+    const emitter = new StreamedEmitter()
+    toThenable(this.renderTemplates(templates, ctx, emitter))
+    return emitter.stream
+  }
   public * renderTemplates (templates: Template[], ctx: Context, emitter?: Emitter): IterableIterator<any> {
     if (!emitter) {
-      emitter = new Emitter(ctx.opts.keepOutputType)
+      emitter = ctx.opts.keepOutputType ? new KeepingTypeEmitter() : new SimpleEmitter()
     }
     for (const tpl of templates) {
       try {
+        // if tpl.render supports emitter, it'll return empty `html`
         const html = yield tpl.render(ctx, emitter)
+        // if not, it'll return an `html`, write to the emitter for it
         html && emitter.write(html)
-        if (emitter.break || emitter.continue) break
+        if (emitter['break'] || emitter['continue']) break
       } catch (e) {
         const err = RenderError.is(e) ? e : new RenderError(e, tpl)
         throw err
       }
     }
-    return emitter.html
+    return emitter.end()
   }
 }