当 gulp-load-plugins 提供时，`gulp-postcss is not a function` 类型错误

Question

当从gulp-load-plugins 的类型定义扩展TypeScirpt 接口IGulpPlugins 或gulp-postcss 的错误定义类型时，我犯了某种错误。

根据index.d.ts 的@types/gulp-load-plugins 中的评论：

/**
 * Extend this interface to use Gulp plugins in your gulpfile.js
 */
interface IGulpPlugins {
}

除了gulp-postcss 之外的所有以下插件都可以使用。

import * as gulpDebug from 'gulp-debug';
import * as gulpPlumber from 'gulp-plumber';
import * as gulpIntercept from 'gulp-intercept';
import * as gulpIf from 'gulp-if';
import * as gulpPug from 'gulp-pug';
import * aas gulpHtmlPrettify from 'gulp-html-prettify';
import * as gulpSass from 'gulp-sass';
import * as gulpStylus from 'gulp-stylus';
import * as gulpSourcemaps from 'gulp-sourcemaps';
import * as gulpPostCss from 'gulp-postcss';

export interface IGulpPlugins {
  plumber: typeof gulpPlumber;
  debug: typeof gulpDebug;
  intercept: typeof gulpIntercept;
  if: typeof gulpIf;
  pug: typeof gulpPug;
  htmlPrettify: typeof gulpHtmlPrettify;
  sass: typeof gulpSass;
  stylus: typeof gulpStylus;
  postCss: typeof gulpPostCss;
  sourcemaps: typeof gulpSourcemaps;
}

以下代码中没有TypseScript编译错误，但是如果执行编译后的TypeScript，则会出现TypeError: gulpPlugins.postCss is not a function错误。

import * as gulp from 'gulp';
import * as GulpPlugins from 'gulp-load-plugins';

// I did not create types for this libary yet, so temporary make TypeScript to ignore it
// @ts-ignore
import * as postcssNormalizeWhitespace from 'postcss-normalize-whitespace';

gulpPlugins: IGulpPlugins = GulpPlugins();

return gulp.src(SOURCE_FILES_GLOB_SELECTION)
    .pipe(gulpPlugins.postCss([postcssNormalizeWhitespace]))
    .pipe(gulp.dest('build'));

如果要写

import * as gulp from 'gulp';
import * as GulpPlugins from 'gulp-load-plugins';

/* When I wrote this question, types in DefinitelyTyped for this library was not exists yet,
 * but I created it. However did not create the pull request yet.
 */
import * as gulpPostCss from 'gulp-postcss';

// I did not create types for this libary yet, so temporary make typescript ingore it
// @ts-ignore
import * as postcssNormalizeWhitespace from 'postcss-normalize-whitespace';


return gulp.src(SOURCE_FILES_GLOB_SELECTION)
    .pipe(gulpPostCss([postcssNormalizeWhitespace]))
    .pipe(gulp.dest('build'));

相反，JavaScript 可以正常工作。

我不明白，我在哪里做错了。 让我重复一遍，扩展 IGulpPl​​ugins 中的所有插件（gulp-postcss 除外）都有效。

我写的gulp-postcss的类型是：

/// <reference types="node"/>
import Vinyl = require('vinyl');

declare function GulpPostCss(plugins?: Array<string>, options?: GulpPostCss.Options): NodeJS.ReadWriteStream;
declare function GulpPostCss(callback?: (file: Vinyl) => { plugins?: Array<string>, options?: GulpPostCss.Options }): NodeJS.ReadWriteStream;

declare namespace GulpPostCss {
    interface Options {
        parser?: string;
    }
}

export = GulpPostCss;

Answer 1

有两件事你没有做对。

1. 您打错字了，或者您可能不明白 gulp-load-plugins 的工作原理。

如果你的插件名称是gulp-post-css，那么它就变成了gulpPlugins.postCss。但是，该插件名称是gulp-postcss，所以它将是：

gulpPlugins.postcss(...) // NOT gulpPlugins.postCss !!!

1. 你不懂打字稿。

这与打字稿无关。

这是一条经验法则：typescript 对 javascript 运行时行为的影响零。每当您发现运行时错误时，它一定来自 typescript 的 javascript 端。

虽然 1. 已经解决了您的问题，但我们假设您必须使用 gulpPlugins.postCss。为了使它起作用，请尝试添加以下行：

import * as gulpPostCss from 'gulp-postcss';
gulpPlugins.postCss = gulpPostCss;

现在它可以工作了。