使用插件权限

The goal of this exercise is to get a better understanding on how
plugin permissions can be enabled or disabled, where they are described
and how to use default permissions of plugins.

At the end you will have the ability to find and use permissions of
arbitrary plugins and understand how to custom tailor existing permissions.
You will have an example Tauri application where a plugin and plugin specific
permissions are used.

Create your Tauri application.
In our example we will facilitate create-tauri-app:
- Bash
- PowerShell
- npm
- Yarn
- pnpm
- deno
- bun
- Cargo
```
sh <(curl https://create.tauri.app/sh)
```
```
irm https://create.tauri.app/ps | iex
```
```
npm create tauri-app@latest
```
```
yarn create tauri-app
```
```
pnpm create tauri-app
```
```
deno run -A npm:create-tauri-app
```
```
bun create tauri-app
```
```
cargo install create-tauri-app --locked
cargo create-tauri-app
```
We will proceed in this step-by-step explanation with pnpm but you can choose another
package manager and replace it in the commands accordingly.
```
pnpm create tauri-app
```
```
✔ Project name · plugin-permission-demo
✔ Choose which language to use for your frontend · TypeScript / JavaScript - (pnpm, yarn, npm, bun)
✔ Choose your package manager · pnpm
✔ Choose your UI template · Vanilla
✔ Choose your UI flavor · TypeScript

Template created! To get started run:
cd plugin-permission-demo
pnpm install
pnpm tauri dev
```
To search for existing plugins you can use multiple resources.

The most straight forward way would be to check out if your plugin is already
in the Plugins section of the documentation and therefore part of Tauri’s
maintained plugin set.
The Filesystem plugin is part of the Tauri plugin workspace and you can add it to
your project by following the instructions.

If the plugin is part of the community effort you can most likely find it
on crates.io when searching for tauri-plugin-<your plugin name>.
If it is an existing plugin from our workspace you can use the automated way:
```
pnpm tauri add fs
```
If you have found it on crates.io
you need to manually add it as a dependency and modify the Tauri builder
to initialize the plugin:
Terminal window
```
cargo add tauri-plugin-fs
```
Modify lib.rs to initialize the plugin:
src-tauri/src/lib.rs
```
#[cfg_attr(mobile, tauri::mobile_entry_point)]
fn run() {
  tauri::Builder::default()
    .plugin(tauri_plugin_fs::init())
    .run(tauri::generate_context!())
    .expect("error while running tauri application");
}
```

Each plugin has a default permission set, which contains
all permissions and scopes to use the plugin out of the box
with a reasonable minimal feature set.

In the case of official maintained plugins you can find a
rendered description in the documentation
(eg. fs default).

In case you are figuring this out for a community plugin you
need to check out the source code of the plugin.
This should be defined in your-plugin/permissions/default.toml.

"$schema" = "schemas/schema.json"

[default]
description = """
# Tauri `fs` default permissions

This configuration file defines the default permissions granted
to the filesystem.

### Granted Permissions

This default permission set enables all read-related commands and
allows access to the `$APP` folder and sub directories created in it.
The location of the `$APP` folder depends on the operating system,
where the application is run.

In general the `$APP` folder needs to be manually created
by the application at runtime, before accessing files or folders
in it is possible.

### Denied Permissions

This default permission set prevents access to critical components
of the Tauri application by default.
On Windows the webview data folder access is denied.

"""
permissions = ["read-all", "scope-app-recursive", "deny-default"]

This step is all about finding the permissions you need to
for your commands to be exposed to the frontend with the minimal
access to your system.

The fs plugin has autogenerated permissions which will disable
or enable individual commands and allow or disable global scopes.

These can be found in the documentation
or in the source code of the plugin (fs/permissions/autogenerated).

Let us assume we want to enable writing to a text file test.txt
located in the users $HOME folder.

For this we would search in the autogenerated permissions for a
permission to enable writing to text files like allow-write-text-file
and then for a scope which would allow us to access the $HOME/test.txt
file.

We need to add these to our capabilities section in our
src-tauri/tauri.conf.json or in a file in the src-tauri/capabilities/ folder.
By default there is already a capability in src-tauri/capabilities/default.json we
can modify.
src-tauri/capabilities/default.json
```
{
  "$schema": "../gen/schemas/desktop-schema.json",
  "identifier": "default",
  "description": "Capability for the main window",
  "windows": [
    "main"
  ],
  "permissions": [
    "path:default",
    "event:default",
    "window:default",
    "app:default",
    "image:default",
    "resources:default",
    "menu:default",
    "tray:default",
    "shell:allow-open",
    "fs:default",
    "fs:allow-write-text-file",
  ]
}
```
Since there are only autogenerated scopes in the fs plugin to
access the full $HOME folder, we need to configure our own scope.
This scope should be only enabled for the write-text-file command
and should only expose our test.txt file.
src-tauri/capabilities/default.json
```
   {
  "$schema": "../gen/schemas/desktop-schema.json",
  "identifier": "default",
  "description": "Capability for the main window",
  "windows": [
    "main"
  ],
  "permissions": [
    "path:default",
    "event:default",
    "window:default",
    "app:default",
    "image:default",
    "resources:default",
    "menu:default",
    "tray:default",
    "shell:allow-open",
    "fs:allow-write-text-file",
    {
      "identifier": "fs:allow-write-text-file",
      "allow": [{ "path": "$HOME/test.txt" }]
    },
  ]
}
```

After we have added the necessary permission we want to
confirm that our application can access the file and write
it’s content.

We can use this snippet in our application to write to the file:

import { writeTextFile, BaseDirectory } from '@tauri-apps/plugin-fs';

let greetInputEl: HTMLInputElement | null;

async function write(message: string) {
    await writeTextFile('test.txt', message, { baseDir: BaseDirectory.Home });
}

window.addEventListener("DOMContentLoaded", () => {
  greetInputEl = document.querySelector("#greet-input");
  document.querySelector("#greet-form")?.addEventListener("submit", (e) => {
    e.preventDefault();
    if (!greetInputEl )
      return;

    write(greetInputEl.value == "" ? "No input provided": greetInputEl.value);

  });
});

Replacing the src/main.ts with this snippet means we do not need to modify the default index.html,
when using the plain Vanilla+Typescript app.
Entering any input into the input field of the running app will be
written to the file on submit.

Let’s test now in practice:

pnpm run tauri dev

After writing into the input and clicking “Submit”,
we can check via our terminal emulator or by manually opening the
file in your home folder.

cat $HOME/test.txt

You should be presented with your input and finished learning about using permissions from plugins in Tauri applications.
🥳

If you encountered this error:

[Error] Unhandled Promise Rejection: fs.write_text_file not allowed. Permissions associated with this command: fs:allow-app-write, fs:allow-app-write-recursive, fs:allow-appcache-write, fs:allow-appcache-write-recursive, fs:allow-appconf...
(anonymous function) (main.ts:5)

Then you very likely did not properly follow the previous instructions.

使用插件权限

Create Tauri Application

Add the file-system Plugin to Your Application

Understand the Default Permissions of the fs Plugin

Find the Right Permissions

Test Permissions in Practice