blocks|key|2854065|text|NPM+docs指出，只有当您的软件包作为依赖项安装时，engines字段才会转换错误：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2854066|除非用户设置了engine-strict配置标志，否则引擎字段仅在您的软件包作为依赖项安装时才会产生警告。|2854067|2854068|作为项目的开发人员/管理员，您应该不会看到来自engines字段的任何警告。|2854069|由于只在运行npm+install时需要编译文件，因此可以简单地使用postinstall钩子。|2854070|还请注意，prepublish会一直存在，它只会在publish钩子之前触发，从而改变它在npm@5上的行为。|2854071|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.npmjs.com/files/package.json#engines^0|S|7|0|8|0|0|7|D|0|0|N|7|0|6|B|Y|B|0|5|A|P|7|19|5|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|F|3|G|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|15|8|@]|D|@]|E|$]]|$1|I|3|J|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|K|3|L|5|6|7|19|8|@$9|1A|A|1B|B|C]|$9|1C|A|1D|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|1E|8|@$9|1F|A|1G|B|C]|$9|1H|A|1I|B|C]|$9|1J|A|1K|B|C]]|D|@]|E|$]]|$1|O|3|-4|5|6|7|1L|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

<a href="https://docs.npmjs.com/files/package.json#engines" rel="nofollow noreferrer">NPM docs</a> state that <code>engines</code> field casts an error only when your package is installed as a dependency:

<blockquote>
 Unless the user has set the <code>engine-strict</code> config flag, [engines] field is advisory only will produce warnings when your package is installed as a dependency.
</blockquote>

As developer/mantainer of the project you should not see any alert coming from your <code>engines</code> field.

Since you need to compile your files when you run <code>npm install</code> only, you might simply use <code>postinstall</code> hook.

Please also note that <code>prepublish</code> is there to stay, it will just change its behaviour on <code>npm@5</code> by firing only before <code>publish</code> hook.

blocks|key|103802|text|我找到了一个使用check-node-version的更好的解决方案；该包有一个命令行界面，使其易于使用。以下是我建议的最佳实践步骤：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|103803|103804|使用npm+install+-D+check-node-version@1添加开发依赖项，|ordered-list-item|103805|将现有的prepublish脚本重命名为prepare，|103806|添加替换的prepublish脚本以处理向后兼容性，并建议升级npm+(见下文)|103807|103808|我的package.json现在看起来像这样：|BOLD|103809|"scripts":+{
++++"prepare":+"npm+run+antlr4+&&+tsc",
++++"prepublish":+"check-node-version+--npm+\">=4\"+%7C%7C+npm+run+prepare",
++++"antlr4":+"rimraf+gen+&&+antlr4ts+Json.g4+-o+gen+-visitor",
++++...
},
"devDependencies":+{
++++"check-node-version":+"%5E1.1.2",
++++...|code-block|syntax|javascript|103810|使用这种方法：|103811|103812|npm+install始终运行prepare脚本，即使安装了npm@3也是如此。如果安装了npm@5，npm@3甚至有一条关于升级npm的有用消息，这应该可以正常工作，但是因为脚本使用%7C%7C+npm+run+prepare来模拟更高版本的行为，所以脚本会在出现错误后继续运行。|unordered-list-item|103813|如果我以后想要对npm@4进行硬依赖，如果在npm@3.|103814|上运行，删除%7C%7C+npm+run+prepare部件将导致脚本停止|103815|下面是使用npm@3构建的样子|103816|C:\code\antlr4ts-json>npm+i

>+antlr4ts-json@1.0.6-alpha+prepublish+C:\code\antlr4ts-json
>+check-node-version+--npm+">=4"+%7C%7C+npm+run+prepare

node:+v6.9.1
npm:+v3.10.10
Error:+Wanted+npm+version+">=4"+(>=4.0.0)
To+install+npm,+run+`npm+install+-g+npm@>=4`

>+antlr4ts-json@1.0.6-alpha+prepare+C:\code\antlr4ts-json
>+npm+run+antlr4+&&+tsc|103817|entityMap|0|LINK|mutability|MUTABLE|url|https://www.npmjs.com/package/check-node-version^0|8|I|8|I|0|0|0|2|Z|0|4|A|K|7|0|5|A|0|0|2|C|0|0|0|0|0|B|F|7|U|5|19|5|1F|5|2K|I|0|8|5|M|5|0|6|I|0|5|5|0|0^^$0|@$1|2|3|4|5|6|7|1I|8|@$9|1J|A|1K|B|C]]|D|@$9|1L|A|1M|1|1N]]|E|$]]|$1|F|3|-4|5|6|7|1O|8|@]|D|@]|E|$]]|$1|G|3|H|5|I|7|1P|8|@$9|1Q|A|1R|B|C]]|D|@]|E|$]]|$1|J|3|K|5|I|7|1S|8|@$9|1T|A|1U|B|C]|$9|1V|A|1W|B|C]]|D|@]|E|$]]|$1|L|3|M|5|I|7|1X|8|@$9|1Y|A|1Z|B|C]]|D|@]|E|$]]|$1|N|3|-4|5|6|7|20|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|21|8|@$9|22|A|23|B|Q]]|D|@]|E|$]]|$1|R|3|S|5|T|7|24|8|@]|D|@]|E|$U|V]]|$1|W|3|X|5|6|7|25|8|@]|D|@]|E|$]]|$1|Y|3|-4|5|6|7|26|8|@]|D|@]|E|$]]|$1|Z|3|10|5|11|7|27|8|@$9|28|A|29|B|C]|$9|2A|A|2B|B|C]|$9|2C|A|2D|B|C]|$9|2E|A|2F|B|C]|$9|2G|A|2H|B|C]|$9|2I|A|2J|B|C]]|D|@]|E|$]]|$1|12|3|13|5|11|7|2K|8|@$9|2L|A|2M|B|C]|$9|2N|A|2O|B|C]]|D|@]|E|$]]|$1|14|3|15|5|6|7|2P|8|@$9|2Q|A|2R|B|C]]|D|@]|E|$]]|$1|16|3|17|5|6|7|2S|8|@$9|2T|A|2U|B|C]]|D|@]|E|$]]|$1|18|3|19|5|T|7|2V|8|@]|D|@]|E|$U|V]]|$1|1A|3|-4|5|6|7|2W|8|@]|D|@]|E|$]]]|1B|$1C|$5|1D|1E|1F|E|$1G|1H]]]]

I found a better solution using <a href="https://www.npmjs.com/package/check-node-version" rel="noreferrer"><code>check-node-version</code></a>; that package has a command line interface, making it easy to use for this purpose. Here are the steps I would propose as a best-practice:

<ol>
<li>Add a development dependency with <code>npm install -D check-node-version@1</code>,</li>
<li>Rename the existing <code>prepublish</code> script to <code>prepare</code>,</li>
<li>Add a replacement <code>prepublish</code> script to handle backward compatibility, and suggest upgrading npm (see below.)</li>
</ol>

My package.json now looks something like this:

<pre><code>"scripts": {
 "prepare": "npm run antlr4 &amp;&amp; tsc",
 "prepublish": "check-node-version --npm \"&gt;=4\" || npm run prepare",
 "antlr4": "rimraf gen &amp;&amp; antlr4ts Json.g4 -o gen -visitor",
 ...
},
"devDependencies": {
 "check-node-version": "^1.1.2",
 ...
</code></pre>

With this approach:

<ul>
<li><code>npm install</code> always runs the <code>prepare</code> script, even with <code>npm@3</code> installed. This should presumably work correctly if <code>npm@5</code> is installed (untested.)</li>
<li>On <code>npm@3</code> there's even a helpful message about upgrading npm, but because the script uses <code>|| npm run prepare</code> to simulate the behavior of later versions, the script continues after the error.</li>
<li>If I later want to take a hard dependency on <code>npm@4</code>, removing the <code>|| npm run prepare</code> part would cause the script to stop if run on <code>npm@3</code>.</li>
</ul>

Here's what a build looks like using <code>npm@3</code>:

<pre><code>C:\code\antlr4ts-json&gt;npm i

&gt; antlr4ts-json@1.0.6-alpha prepublish C:\code\antlr4ts-json
&gt; check-node-version --npm "&gt;=4" || npm run prepare

node: v6.9.1
npm: v3.10.10
Error: Wanted npm version "&gt;=4" (&gt;=4.0.0)
To install npm, run `npm install -g npm@&gt;=4`

&gt; antlr4ts-json@1.0.6-alpha prepare C:\code\antlr4ts-json
&gt; npm run antlr4 &amp;&amp; tsc
</code></pre>

I run <code>npm install</code> from <a href="https://github.com/BurtHarris/antlr4ts-json" rel="noreferrer">my sample project's</a> root folder to build it using scripts in <code>package.json</code>. 

The build requires a few transpilation steps currently in the <code>prepublish</code> script, but npm version 4 displays a warning that a breaking change is coming, leading me to believe the new <code>prepare</code> build event script is more future proof. 

<pre><code>C:\code\antlr4ts-json&gt;npm install
npm WARN prepublish-on-install As of npm@5, `prepublish` scripts will run only for `npm publish`.
npm WARN prepublish-on-install (In npm@4 and previous versions, it also runs for `npm install`.)
npm WARN prepublish-on-install See the deprecation note in `npm help scripts` for more information.
...
</code></pre>

Unfortunately, simply moving the script from <code>prepublish</code> to <code>prepare</code> breaks backward compatibility: If someone runs <code>npm install</code> using <code>npm@3</code>, the build steps in <code>prepare</code> are silently ignored. 

What's the best practice for upgrading my build-time script? Ideally, I'd like to update my <code>package.json</code> so that <code>npm install</code> works for any npm@>=3, but alternatively generating a clear error message indicating that npm@>=4 is required at when <code>npm install</code> is run using npm@3 would be perfectly acceptable. 

Bakground: I tried including 

<pre><code>"engines": { "npm": "&gt;=4.0.0" },
</code></pre>

Thanks to @toomuchdesign (and others), I understand why this doesn't do what I want; <code>engines</code> only checks when my package is installed as a dependency, not someone builds it from sources. That makes sense.

I tracked the background on this planned change down to <a href="https://github.com/npm/npm/issues/10074" rel="noreferrer">npm issue #10074</a>, which explains why a breaking change is needed. However I'm still unclear how to handle the transition better.

Best practice for upgrading npm `prepublish` script for npm@>=4

我从根文件夹运行npm install，使用package.json中的脚本构建它。构建需要几个当前在prepublish脚本中的转换步骤，但是npm version4显示了一个即将发生重大变化的警告，这让我相信新的prepare构建事件脚本更适合未来。C:\code\antlr4ts-json>npm install...

问升级npm@>=4的npm `prepublish`脚本的最佳实践
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