uvx/uv tool run: Add context message before listing available tools w…

…hen no arguments are provided (#7641)

## Summary

Adds a helpful context message when `uvx` is run without arguments
To clarify, it is displaying the installed tools.

This addresses confusion, such as the one highlighted in issue #7348,
by making the output more user-friendly and informative.

Related #4024 

## Test Plan

Updated the test snapshots to include the new output.
Running the tests locally with `cargo nextest run` confirms that the
tests pass.
The CI pipeline should also pass.

### Manuel Testing

**uvx**
```shell
# Make sure you have the updated version of uv installed on your path.
# cargo install --path ./crates/uv --force
❯ uvx
Provide a command to invoke with `uvx <command>` or `uvx --from <package> <command>`.

The following tools are already installed:

black v24.8.0
- black
- blackd
ruff v0.6.7
- ruff

See `uvx --help` for more information.
```

**uv tool list**
```shell
# Make sure you have the updated version of uv installed on your path.
# cargo install --path ./crates/uv --force
❯ uv tool list
black v24.8.0
- black
- blackd
ruff v0.6.7
- ruff
```

**uv tool run**
```shell
# Make sure you have the updated version of uv installed on your path.
# cargo install --path ./crates/uv --force
❯ uv tool run
Provide a command to invoke with `uv tool run <command>` or `uv tool run --from <package> <command>`.

The following tools are already installed:

black v24.8.0
- black
- blackd
ruff v0.6.7
- ruff

See `uv tool run --help` for more information.
```
---

Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>

---------

Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>

crates/uv/src/commands/tool/run.rs

@@ -36,9 +36,7 @@ use crate::commands::pip::operations;
 use crate::commands::project::{resolve_names, EnvironmentSpecification, ProjectError};
 use crate::commands::reporters::PythonDownloadReporter;
 use crate::commands::tool::Target;
-use crate::commands::{
-    project::environment::CachedEnvironment, tool::common::matching_packages, tool_list,
-};
+use crate::commands::{project::environment::CachedEnvironment, tool::common::matching_packages};
 use crate::commands::{ExitStatus, SharedState};
 use crate::printer::Printer;
 use crate::settings::ResolverInstallerSettings;
@@ -79,9 +77,13 @@ pub(crate) async fn run(
     cache: Cache,
     printer: Printer,
 ) -> anyhow::Result<ExitStatus> {
-    // treat empty command as `uv tool list`
+    // Treat empty command similar to `uv tool list`, list available tools.
     let Some(command) = command else {
-        return tool_list(false, false, &cache, printer).await;
+        match list_available_tools(invocation_source, &cache, printer).await {
+            // It is a failure because user misses a required tool name.
+            Ok(()) => return Ok(ExitStatus::Error),
+            Err(err) => return Err(err),
+        };
     };
 
     let (target, args) = command.split();
@@ -262,6 +264,77 @@ fn get_entrypoints(
     )?)
 }
 
+/// Display a list of tools that provide the executable.
+///
+/// If there is no package providing the executable, we will display a message to how to install a package.
+async fn list_available_tools(
+    invocation_source: ToolRunCommand,
+    cache: &Cache,
+    printer: Printer,
+) -> anyhow::Result<()> {
+    writeln!(
+        printer.stdout(),
+        "Provide a command to invoke with `{invocation_source} <command>` \
+            or `{invocation_source} --from <package> <command>`.\n"
+    )?;
+
+    let installed_tools = InstalledTools::from_settings()?;
+    let no_tools_installed_msg =
+        "No tools installed. See `uv tool install --help` for more information.";
+    let _lock = match installed_tools.lock().await {
+        Ok(lock) => lock,
+        Err(uv_tool::Error::Io(err)) if err.kind() == std::io::ErrorKind::NotFound => {
+            writeln!(printer.stdout(), "{no_tools_installed_msg}")?;
+            return Ok(());
+        }
+        Err(err) => return Err(err.into()),
+    };
+
+    let mut tools = installed_tools.tools()?.into_iter().collect::<Vec<_>>();
+    tools.sort_by_key(|(name, _)| name.clone());
+
+    if tools.is_empty() {
+        writeln!(printer.stdout(), "{no_tools_installed_msg}")?;
+        return Ok(());
+    }
+
+    let mut buf = String::new();
+    for (name, tool) in tools {
+        // Skip invalid tools.
+        let Ok(tool) = tool else {
+            continue;
+        };
+
+        // Output tool name and version.
+        let Ok(version) = installed_tools.version(&name, cache) else {
+            continue;
+        };
+        writeln!(buf, "{}", format!("{name} v{version}").bold())?;
+
+        // Output tool entrypoints.
+        for entrypoint in tool.entrypoints() {
+            writeln!(buf, "- {}", entrypoint.name)?;
+        }
+    }
+
+    // Installed tools were malformed or failed fetching versions.
+    if buf.is_empty() {
+        writeln!(printer.stderr(), "{no_tools_installed_msg}")?;
+        return Ok(());
+    }
+
+    writeln!(
+        printer.stdout(),
+        "The following tools are already installed:\n"
+    )?;
+    writeln!(printer.stdout(), "{buf}")?;
+    writeln!(
+        printer.stdout(),
+        "See `{invocation_source} --help` for more information."
+    )?;
+    Ok(())
+}
+
 /// Display a warning if an executable is not provided by package.
 ///
 /// If found in a dependency of the requested package instead of the requested package itself, we will hint to use that instead.

crates/uv/tests/tool_run.rs

@@ -750,12 +750,14 @@ fn tool_run_list_installed() {
     uv_snapshot!(context.filters(), context.tool_run()
         .env("UV_TOOL_DIR", tool_dir.as_os_str())
         .env("XDG_BIN_HOME", bin_dir.as_os_str()), @r###"
-    success: true
-    exit_code: 0
+    success: false
+    exit_code: 2
     ----- stdout -----
+    Provide a command to invoke with `uv tool run <command>` or `uv tool run --from <package> <command>`.
+
+    No tools installed. See `uv tool install --help` for more information.
 
     ----- stderr -----
-    No tools installed
     "###);
 
     // Install `black`.
@@ -771,13 +773,19 @@ fn tool_run_list_installed() {
     uv_snapshot!(context.filters(), context.tool_run()
         .env("UV_TOOL_DIR", tool_dir.as_os_str())
         .env("XDG_BIN_HOME", bin_dir.as_os_str()), @r###"
-    success: true
-    exit_code: 0
+    success: false
+    exit_code: 2
     ----- stdout -----
+    Provide a command to invoke with `uv tool run <command>` or `uv tool run --from <package> <command>`.
+
+    The following tools are already installed:
+
     black v24.2.0
     - black
     - blackd
 
+    See `uv tool run --help` for more information.
+
     ----- stderr -----
     "###);
 }
@@ -891,9 +899,8 @@ fn tool_run_with_editable() -> anyhow::Result<()> {
     "###);
 
     // Requesting an editable requirement should install it in a layer, even if it satisfied
-    uv_snapshot!(context.filters(), context.tool_run().arg("--with-editable").arg("./src/anyio_local").arg("flask").arg("--version").env("UV_TOOL_DIR", tool_dir.as_os_str()).env("XDG_BIN_HOME", bin_dir.as_os_str())
-
-    , @r###"
+    uv_snapshot!(context.filters(), context.tool_run().arg("--with-editable").arg("./src/anyio_local").arg("flask").arg("--version").env("UV_TOOL_DIR", tool_dir.as_os_str()).env("XDG_BIN_HOME", bin_dir.as_os_str()),
+    @r###"
     success: true
     exit_code: 0
     ----- stdout -----