NET Core 2.1 Global Tools

微软工程师Nate McMaster的博文.NET Core 2.1 Global Tools

https://natemcmaster.com/blog/2018/05/12/dotnet-global-tools/

Getting started with creating a .NET Core global tool package. Also, a peek under the hood.

.NET Core 2.1 RC1 was released this week. This is the first supported version of the .NET Core CLI which includes a feature called “.NET Core Global Tools”. This feature provides a simple way to create and share cross-platform console tools. In this post, I’ll go over some of the basics, and then walk though what is going on under the hood. You will need to download .NET Core 2.1 to use this to try this on your own.

Tip: For a real-world example of a global tool, see https://github.com/natemcmaster/dotnet-serve/.

Basic design

A .NET Core global tool is a special NuGet package that contains a console application. When installing a tool, .NET Core CLI will download and make your console tool available as a new command.

Users install tools by executing “dotnet tool install”:

dotnet tool install -g awesome-tool

Once installed, the command “awesome-tool” can now be used.

awesome-tool

Creating your own package

To simplify getting started, I’ve created a project templates.

Install the templates package

dotnet new --install McMaster.DotNet.GlobalTool.Templates

Create a new project

dotnet new global-tool --command-name awesome-tool

Once you have this project, you can create your tool package like this:

dotnet pack --output ./

This creates a file named awesome-tool.1.0.0.nupkg You can install your package like this:

dotnet tool install -g awesome-tool --add-source ./

When you are ready to share with world, upload the package to https://nuget.org.

Note: in 2.1 RC1, use --source-feed instead of --add-source. This was renamed in https://github.com/dotnet/cli/pull/9164

Additional commands

dotnet tool has other commands you can invoke. For example,

dotnet tool list -g

dotnet tool uninstall -g awesome-tool

dotnet tool update -g awesome-tool

Under the hood

The NuGet package that contains the tool is produced by running dotnet publish and putting everything in publish output into the NuGet package, with a few manifest files.

When dotnet tool install --global executes, it…

uses dotnet restore with special parameters to fetch the package.

extracts the package into $HOME/.dotnet/.store/(package id)/(version)

Generates an executable in $HOME/.dotnet/tools

The executable generated is a small console app (written in C++) which automatically knows how to find your .NET Core .dll file and launch it.

When dotnet tool install --tool-path $installDir executes, it does the same thing, but installs into $installDir, not $HOME/.dotnet/tools

Package authoring and SDK

Authoring a global tool requires the .NET Core SDK. This SDK provides a few simple settings to control the naming and contents of a .NET Core global tool package.

The required minimum project for a global tool looks like this.

true
Exe
netcoreapp2.1

Additional properties can be set to control the generated tool.

ToolCommandName - the command name users will invoke. It defaults to the name of the .dll file produced (i.e. assembly name)

This does not need to start with dotnet-. It can be anything without spaces.

If it begins with dotnet-, it can be used as a subcommand on dotnet, provided that command doesn’t already exist. Example: dotnet-serve can be invoked as either dotnet serve or dotnet-serve.

PackageId - the ID of the NuGet package (defaults to the .csproj file name)

The package ID can be different than the command name and assembly name

PackageVersion - the version of the NuGet package (defaults to 1.0.0)

AssemblyName - can be used to change the file name of the .dll file

Example of using these properties:

true
Exe
netcoreapp2.1
pineapple
dole-cli
1.0.0-alpha-$(BuildNumber)
Dole.Cli

Deep-dive: package requirements
There are some very specific requirements for global tools. The SDK takes care of most of these for you when you specify PackAsTool=true.

Publish output into pack

As mentioned above, the tools package must contain all your apps dependencies. This can be collected into one place by using dotnet publish. By default, dotnet pack only contains the output of dotnet build. This output does not normally contain third-party assemblies, static files, and the DotnetToolSettings.xml file, which is why you need to specify PackAsTool. This instructs the SDK to gather all publish output, not just assembly you compile.

DotnetToolSettings.xml

This file must exist in the package. If not install will fail with

The settings file in the tool’s NuGet package is invalid: Settings file ‘DotnetToolSettings.xml’ was not found in the package.

The schema for this file looks like this:

Currently, there are many restrictions on how this file can be used.

The file must exist in the NuGet package under tools/$targetframework/any/. Example: tools/netcoreapp2.1/any/DotnetToolSettings.xml.

You may only specify one DotnetToolSettings.xml file per package.

You may only specify one per DotnetToolSettings.xml file.

The only allowed value for Runner is "dotnet".

The value for EntryPoint must be a .dll file that sits next to DotnetToolSettings.xml in the package.

Error NU1212 and package type

Installation may fail with this error

error NU1212: Invalid project-package combination for awesome-tool 1.0.0. DotnetToolReference project style can only contain references of the DotnetTool type

This error message is not very clear (see https://github.com/NuGet/Home/issues/6630 for improvement). What this means is that dotnet-tool-install is currently restricted to only installing a .NET Core package that has specific metadata. That metadata can be defined in your nuspec file and must be set as follows:

Dependencies
You must redistribute any of your dependencies in your tools package. Dependencies defined in the metadata of your NuGet package are not honored by dotnet-tool-install.

Common errors

Here are some common errors encountered when using global tools.

PATH and command not after installing

dotnet tool install -g awesome-tool

awesome-tool

awesome-tool: command not found

awesome-tool : The term 'awesome-tool' is not recognized as the name of a cmdlet, function, script file, or operable program.

Global tools are actually “user global”, and are installed to %USERPROFILE%.dotnet\tools (Windows) or $HOME/.dotnet/tools (macOS/Linux). The .NET Core CLI tool makes a best effort to help you ensure this is in your PATH environment variable. However, this can easily be broken. For instance:

if you have set the DOTNET_SKIP_FIRST_TIME_EXPERIENCE environment variable to speed up intial runs of .NET Core, then your PATH may not be updated on first use

macOS: if you install the CLI via .tar.gz and not .pkg, you’ll be missing the /etc/paths.d/dotnet-cli-tool file that configures PATH.

Linux: you will need to edit your shell environment file. e.g. ~/.bash_profile or ~/.zshrc

Workarounds

(May require restarting your shell.)

Windows:

setx PATH "$env:PATH;$env:USERPROFILE/.dotnet/tools"

Linux/macOS:

echo "export PATH="$PATH:$HOME/.dotnet/tools"" >> ~/.bash_profile

Tools are user-specific, not machine global

The .NET Core CLI installs global tools to $HOME/.dotnet/tools (Linux/macOS) or %USERPROFILE%.dotnet\tools (Windows). This means you cannot install a global tool for the entire machine using dotnet tool install --global. Installed tools are only available to the user who installed them.

Installing the .NET Core CLI into a non-default location

If you download the .NET Core CLI as a .zip/.tar.gz and extract it to a non default location, then you may encounter an error after installing and launching a tool:

Windows: A fatal error occurred, the required library hostfxr.dll could not be found

Linux: A fatal error occurred, the required library libhostfxr.so could not be found

macOS: A fatal error occurred, the required library libhostfxr.dylib could not be found

The error will also contain additional details such as:

If this is a self-contained application, that library should exist in [some path here].

If this is a framework-dependent application, install the runtime in the default location [default location] or use the DOTNET_ROOT environment variable to specify the runtime location.

The reason this happens is that the generated shim created by dotnet tool install only searchs for .NET Core in the default install locations. You can override the default location by setting the DOTNET_ROOT environment variable.

set DOTNET_ROOT=C:\Users\nate\dotnet

export DOTNET_ROOT=/Users/nate/Downloads/dotnet

See https://github.com/dotnet/cli/issues/9114 for more details.

Wrapping up

This is an awesome feature. Super happy the .NET Core CLI team created it. Can’t wait to see what people make.

用过npm开发都知道，npm包都可以以全局的方式安装，例如安装一个http-server服务，可以使用npm i http-server -g来将http-server包安装到全局环境。安装完之后，就可以通过cmd或者powershell运行全局工具http-server命令，来使用静态托管服务。dotnet tool 就是一个类似npm全局工具的新特性，在.net core2.1正式加入。它的详细使用方法可在微软官方文档查看，本文主要介绍如何编写一个global tool并发布至nuget。

安装.net core 2.1

安装最新版.net core SDK 可前往DotNet官方站点的下载页面，下载完成后双击安装即可。安装完成后打开cmd运行dotnet --version 返回版本大于或等于2.1.300表示安装成功。

安装global tool 项目模板

打开cmd 键入dotnet new --install McMaster.DotNet.GlobalTool.Templates安装完成后运行dotnet new

模板 短名称 语言 标记

Console Application console [C#], F#, VB Common/Console

Class library classlib [C#], F#, VB Common/Library

.NET Core Global Console Tool global-tool [C#] Console/Empty

Unit Test Project mstest [C#], F#, VB Test/MSTest

xUnit Test Project xunit [C#], F#, VB Test/xUnit

Razor Page page [C#] Web/ASP.NET

MVC ViewImports viewimports [C#] Web/ASP.NET

MVC ViewStart viewstart [C#] Web/ASP.NET

ASP.NET Core Empty web [C#], F# Web/Empty

ASP.NET Core Web App (Model-View-Controller) mvc [C#], F# Web/MVC

ASP.NET Core Web App razor [C#] Web/MVC/Razor Pages

ASP.NET Core with Angular angular [C#] Web/MVC/SPA

ASP.NET Core with React.js react [C#] Web/MVC/SPA

ASP.NET Core with React.js and Redux reactredux [C#] Web/MVC/SPA

Razor Class Library razorclasslib [C#] Web/Razor/Library/Razor Class Library

ASP.NET Core Web API webapi [C#], F# Web/WebAPI

global.json file globaljson Config

NuGet Config nugetconfig Config

Web Config webconfig Config

Solution File sln Solution

多出一个global-tool模板

.NET Core Global Console Tool global-tool [C#] Console/Empty

编写一个网页下载工具

接下来通过编写一个网页下载的小工具来演示global tool的创建过程，此小工具的功能是根据网址，下载相应的页面html并保存为文件。

首先新建一个WebDownloader文件夹。在文件夹中运行dotnet new global-tool生成项目如下

obj

Program.cs

WebDownloader.csproj

打开WebDownloader.csproj修改为

web-downloader
True
Exe
netcoreapp2.1

打开Program.cs修改为

using System;

using System.ComponentModel.DataAnnotations;

using System.IO;

using System.Net.Http;

using McMaster.Extensions.CommandLineUtils;

namespace WebDownloader

{

[Command(Description = "网页下载小工具")]

class Program

{

public static int Main(string[] args) => CommandLineApplication.Execute(args);

    [Argument(0, Description = "网址")]
    [Required]
    public string Url { get; }

    [Option(Description = "保存路径")]
    public string Path { get; } = "./";

    [Option(Description = "文件名")]
    public string Name { get; } = "content.txt";

    private int OnExecute()
    {
        var client = new HttpClient();
        var content = client.GetStringAsync(Url).Result;
        var path = System.IO.Path.Combine(Path, Name);
        File.WriteAllText(path, content);
        return 0;
    }
}

}

修改完成后全部保存文件，运行dotnet pack -o ./会在项目根目录生成一个WebDownloader.1.0.0.nupkg包。此包就是最终的nuget包，可上传至nuget.org共享。

为了测试，我们直接将此包安装至本地计算机。运行dotnet tool install WebDownloader -g --add-source ./完成安装。运行web-downloader -h可以看到项目帮助文档

网页下载小工具

Usage: WebDownloader [arguments] [options]

Arguments:

Url 网址

Options:

-p|--path 保存路径

-n|--name 文件名

-?|-h|--help Show help information

运行web-downloader http://www.sina.com后我们发现项目根目录生成了一个content.txt文件内容为新浪的首页html

新浪首页

...
...
如果不再使用此工具通过dotnet tool uninstall WebDownloader -g卸载即可。