Move uvx shell completion to uvx --generate-shell-completion (#7511)

## Summary

Because a problem was found with Powershell and combining the generated
completion scripts for uv and uvx, let's try separating uv and uvx
command completion scripts.

The generated powershell script template can be seen in clap_complete
source, and it starts with `using` directives, which makes it impossible
(apparently) to concatenate two of those script outputs.

As a side effect, this is available under `uv tool run
--generate-shell-completion` too.

Fixes #7482

## Test Plan

- `eval "$(cargo run --bin uvx -- --generate-shell-completion bash)"`
- Test Powershell

.github/workflows/ci.yml

@@ -197,6 +197,13 @@ jobs:
           $uv venv
           $uv pip install ruff
 
+      - name: "Smoke test completion"
+        run: |
+          uv="./target/debug/uv"
+          uvx="./target/debug/uvx"
+          eval "$($uv generate-shell-completion bash)"
+          eval "$($uvx --generate-shell-completion bash)"
+
   cargo-test-macos:
     timeout-minutes: 10
     needs: determine_changes
@@ -296,6 +303,18 @@ jobs:
           uv venv
           uv pip install ruff
 
+      - name: "Smoke test completion"
+        working-directory: ${{ env.UV_WORKSPACE }}
+        shell: powershell
+        env:
+          # Avoid debug build stack overflows.
+          UV_STACK_SIZE: 2000000
+        run: |
+          Set-Alias -Name uv -Value ./target/debug/uv
+          Set-Alias -Name uvx -Value ./target/debug/uvx
+          (& uv generate-shell-completion powershell) | Out-String | Invoke-Expression
+          (& uvx --generate-shell-completion powershell) | Out-String | Invoke-Expression
+
   # Separate jobs for the nightly crate
   windows-trampoline-check:
     timeout-minutes: 10

crates/uv-cli/src/lib.rs

@@ -3247,6 +3247,9 @@ pub struct ToolRunArgs {
     /// By default, environment modifications are omitted, but enabled under `--verbose`.
     #[arg(long, env = "UV_SHOW_RESOLUTION", value_parser = clap::builder::BoolishValueParser::new(), hide = true)]
     pub show_resolution: bool,
+
+    #[arg(long, hide = true)]
+    pub generate_shell_completion: Option<clap_complete_command::Shell>,
 }
 
 #[derive(Args)]

crates/uv/src/lib.rs

@@ -780,30 +780,7 @@ async fn run(cli: Cli) -> Result<ExitStatus> {
             Ok(ExitStatus::Success)
         }
         Commands::GenerateShellCompletion(args) => {
-            // uv
             args.shell.generate(&mut Cli::command(), &mut stdout());
-
-            // uvx: combine `uv tool uvx` with the top-level arguments
-            let mut uvx = Cli::command()
-                .find_subcommand("tool")
-                .unwrap()
-                .find_subcommand("uvx")
-                .unwrap()
-                .clone()
-                // Avoid duplicating the `--help` and `--version` flags from the top-level arguments.
-                .disable_help_flag(true)
-                .disable_version_flag(true)
-                .version(env!("CARGO_PKG_VERSION"));
-
-            // Copy the top-level arguments into the `uvx` command. (Like `Args::augment_args`, but
-            // expanded to skip collisions.)
-            for arg in TopLevelArgs::command().get_arguments() {
-                if arg.get_id() != "isolated" {
-                    uvx = uvx.arg(arg);
-                }
-            }
-            args.shell.generate(&mut uvx, &mut stdout());
-
             Ok(ExitStatus::Success)
         }
         Commands::Tool(ToolNamespace {
@@ -816,6 +793,30 @@ async fn run(cli: Cli) -> Result<ExitStatus> {
                 _ => unreachable!(),
             };
 
+            if let Some(shell) = args.generate_shell_completion {
+                // uvx: combine `uv tool uvx` with the top-level arguments
+                let mut uvx = Cli::command()
+                    .find_subcommand("tool")
+                    .unwrap()
+                    .find_subcommand("uvx")
+                    .unwrap()
+                    .clone()
+                    // Avoid duplicating the `--help` and `--version` flags from the top-level arguments.
+                    .disable_help_flag(true)
+                    .disable_version_flag(true)
+                    .version(env!("CARGO_PKG_VERSION"));
+
+                // Copy the top-level arguments into the `uvx` command. (Like `Args::augment_args`, but
+                // expanded to skip collisions.)
+                for arg in TopLevelArgs::command().get_arguments() {
+                    if arg.get_id() != "isolated" {
+                        uvx = uvx.arg(arg);
+                    }
+                }
+                shell.generate(&mut uvx, &mut stdout());
+                return Ok(ExitStatus::Success);
+            }
+
             // Resolve the settings from the command-line arguments and workspace configuration.
             let args = settings::ToolRunSettings::resolve(args, filesystem, invocation_source);
             show_settings!(args);

crates/uv/src/settings.rs

@@ -319,6 +319,7 @@ impl ToolRunSettings {
             build,
             refresh,
             python,
+            generate_shell_completion: _,
         } = args;
 
         // If `--upgrade` was passed explicitly, warn.

docs/getting-started/installation.md

@@ -186,6 +186,24 @@ To enable shell autocompletion for uv commands, run one of the following:
     Add-Content -Path $PROFILE -Value '(& uv generate-shell-completion powershell) | Out-String | Invoke-Expression'
     ```
 
+To enable shell autocompletion for uvx, run one of the following:
+
+=== "Linux and macOS"
+
+    ```bash
+    # Determine your shell (e.g., with `echo $SHELL`), then run one of:
+    echo 'eval "$(uvx --generate-shell-completion bash)"' >> ~/.bashrc
+    echo 'eval "$(uvx --generate-shell-completion zsh)"' >> ~/.zshrc
+    echo 'uvx --generate-shell-completion fish | source' >> ~/.config/fish/config.fish
+    echo 'eval (uvx --generate-shell-completion elvish | slurp)' >> ~/.elvish/rc.elv
+    ```
+
+=== "Windows"
+
+    ```powershell
+    Add-Content -Path $PROFILE -Value '(& uvx --generate-shell-completion powershell) | Out-String | Invoke-Expression'
+    ```
+
 Then restart the shell or source the shell config file.
 
 ## Uninstallation