Rollup merge of #135950 - Kobzol:tidy-python-improvements, r=onur-ozkan

Tidy Python improvements

Fixes display of Python formatting diffs in tidy, and refactors the code to make it simpler and more robust. Also documents Python formatting and linting in the Rustc dev guide.

Fixes: #135942

r? `@onur-ozkan`

Author: matthiaskrgr

Diff for: src/doc/rustc-dev-guide/src/conventions.md

@@ -1,4 +1,4 @@
-This file offers some tips on the coding conventions for rustc.  This
+This file offers some tips on the coding conventions for rustc. This
 chapter covers [formatting](#formatting), [coding for correctness](#cc),
 [using crates from crates.io](#cio), and some tips on
 [structuring your PR for easy review](#er).
@@ -25,6 +25,7 @@ pass the <!-- date-check: nov 2022 --> `--edition=2021` argument yourself when c
 `rustfmt` directly.
 
 [fmt]: https://github.com/rust-dev-tools/fmt-rfcs
+
 [`rustfmt`]:https://github.com/rust-lang/rustfmt
 
 ## Formatting C++ code
@@ -40,6 +41,26 @@ When modifying that code, use this command to format it:
 This uses a pinned version of `clang-format`, to avoid relying on the local
 environment.
 
+## Formatting and linting Python code
+
+The Rust repository contains quite a lof of Python code. We try to keep
+it both linted and formatted by the [ruff][ruff] tool.
+
+When modifying Python code, use this command to format it:
+```sh
+./x test tidy --extra-checks=py:fmt --bless
+```
+
+and the following command to run lints:
+```sh
+./x test tidy --extra-checks=py:lint
+```
+
+This uses a pinned version of `ruff`, to avoid relying on the local
+environment.
+
+[ruff]: https://github.com/astral-sh/ruff
+
 <a id="copyright"></a>
 
 <!-- REUSE-IgnoreStart -->
@@ -84,7 +105,7 @@ Using `_` in a match is convenient, but it means that when new
 variants are added to the enum, they may not get handled correctly.
 Ask yourself: if a new variant were added to this enum, what's the
 chance that it would want to use the `_` code, versus having some
-other treatment?  Unless the answer is "low", then prefer an
+other treatment? Unless the answer is "low", then prefer an
 exhaustive match. (The same advice applies to `if let` and `while
 let`, which are effectively tests for a single variant.)
 
@@ -124,7 +145,7 @@ See the [crates.io dependencies][crates] section.
 # How to structure your PR
 
 How you prepare the commits in your PR can make a big difference for the
-reviewer.  Here are some tips.
+reviewer. Here are some tips.
 
 **Isolate "pure refactorings" into their own commit.** For example, if
 you rename a method, then put that rename into its own commit, along
@@ -165,4 +186,5 @@ to the compiler.
   crate-related, often the spelling is changed to `krate`.
 
 [tcx]: ./ty.md
+
 [crates]: ./crates-io.md

Diff for: src/tools/tidy/src/ext_tool_checks.rs

@@ -89,74 +89,45 @@ fn check_impl(
 
     if python_lint {
         eprintln!("linting python files");
-        let mut cfg_args_ruff = cfg_args.clone();
-        let mut file_args_ruff = file_args.clone();
-
-        let mut cfg_path = root_path.to_owned();
-        cfg_path.extend(RUFF_CONFIG_PATH);
-        let mut cache_dir = outdir.to_owned();
-        cache_dir.extend(RUFF_CACHE_PATH);
-
-        cfg_args_ruff.extend([
-            "--config".as_ref(),
-            cfg_path.as_os_str(),
-            "--cache-dir".as_ref(),
-            cache_dir.as_os_str(),
-        ]);
-
-        if file_args_ruff.is_empty() {
-            file_args_ruff.push(root_path.as_os_str());
-        }
-
-        let mut args = merge_args(&cfg_args_ruff, &file_args_ruff);
-        args.insert(0, "check".as_ref());
-        let res = py_runner(py_path.as_ref().unwrap(), true, None, "ruff", &args);
+        let py_path = py_path.as_ref().unwrap();
+        let res = run_ruff(root_path, outdir, py_path, &cfg_args, &file_args, &["check".as_ref()]);
 
         if res.is_err() && show_diff {
             eprintln!("\npython linting failed! Printing diff suggestions:");
 
-            args.insert(1, "--diff".as_ref());
-            let _ = py_runner(py_path.as_ref().unwrap(), true, None, "ruff", &args);
+            let _ = run_ruff(root_path, outdir, py_path, &cfg_args, &file_args, &[
+                "check".as_ref(),
+                "--diff".as_ref(),
+            ]);
         }
         // Rethrow error
         let _ = res?;
     }
 
     if python_fmt {
-        let mut cfg_args_ruff = cfg_args.clone();
-        let mut file_args_ruff = file_args.clone();
-
+        let mut args: Vec<&OsStr> = vec!["format".as_ref()];
         if bless {
             eprintln!("formatting python files");
         } else {
             eprintln!("checking python file formatting");
-            cfg_args_ruff.push("--check".as_ref());
-        }
-
-        let mut cfg_path = root_path.to_owned();
-        cfg_path.extend(RUFF_CONFIG_PATH);
-        let mut cache_dir = outdir.to_owned();
-        cache_dir.extend(RUFF_CACHE_PATH);
-
-        cfg_args_ruff.extend(["--config".as_ref(), cfg_path.as_os_str()]);
-
-        if file_args_ruff.is_empty() {
-            file_args_ruff.push(root_path.as_os_str());
+            args.push("--check".as_ref());
         }
 
-        let mut args = merge_args(&cfg_args_ruff, &file_args_ruff);
-        args.insert(0, "format".as_ref());
-        let res = py_runner(py_path.as_ref().unwrap(), true, None, "ruff", &args);
+        let py_path = py_path.as_ref().unwrap();
+        let res = run_ruff(root_path, outdir, py_path, &cfg_args, &file_args, &args);
 
-        if res.is_err() && show_diff {
-            eprintln!("\npython formatting does not match! Printing diff:");
-
-            args.insert(0, "--diff".as_ref());
-            let _ = py_runner(py_path.as_ref().unwrap(), true, None, "ruff", &args);
-        }
         if res.is_err() && !bless {
+            if show_diff {
+                eprintln!("\npython formatting does not match! Printing diff:");
+
+                let _ = run_ruff(root_path, outdir, py_path, &cfg_args, &file_args, &[
+                    "format".as_ref(),
+                    "--diff".as_ref(),
+                ]);
+            }
             eprintln!("rerun tidy with `--extra-checks=py:fmt --bless` to reformat Python code");
         }
+
         // Rethrow error
         let _ = res?;
     }
@@ -247,6 +218,38 @@ fn check_impl(
     Ok(())
 }
 
+fn run_ruff(
+    root_path: &Path,
+    outdir: &Path,
+    py_path: &Path,
+    cfg_args: &[&OsStr],
+    file_args: &[&OsStr],
+    ruff_args: &[&OsStr],
+) -> Result<(), Error> {
+    let mut cfg_args_ruff = cfg_args.into_iter().copied().collect::<Vec<_>>();
+    let mut file_args_ruff = file_args.into_iter().copied().collect::<Vec<_>>();
+
+    let mut cfg_path = root_path.to_owned();
+    cfg_path.extend(RUFF_CONFIG_PATH);
+    let mut cache_dir = outdir.to_owned();
+    cache_dir.extend(RUFF_CACHE_PATH);
+
+    cfg_args_ruff.extend([
+        "--config".as_ref(),
+        cfg_path.as_os_str(),
+        "--cache-dir".as_ref(),
+        cache_dir.as_os_str(),
+    ]);
+
+    if file_args_ruff.is_empty() {
+        file_args_ruff.push(root_path.as_os_str());
+    }
+
+    let mut args: Vec<&OsStr> = ruff_args.into_iter().copied().collect();
+    args.extend(merge_args(&cfg_args_ruff, &file_args_ruff));
+    py_runner(py_path, true, None, "ruff", &args)
+}
+
 /// Helper to create `cfg1 cfg2 -- file1 file2` output
 fn merge_args<'a>(cfg_args: &[&'a OsStr], file_args: &[&'a OsStr]) -> Vec<&'a OsStr> {
     let mut args = cfg_args.to_owned();
@@ -321,8 +324,16 @@ fn get_or_create_venv(venv_path: &Path, src_reqs_path: &Path) -> Result<PathBuf,
 fn create_venv_at_path(path: &Path) -> Result<(), Error> {
     /// Preferred python versions in order. Newest to oldest then current
     /// development versions
-    const TRY_PY: &[&str] =
-        &["python3.11", "python3.10", "python3.9", "python3", "python", "python3.12", "python3.13"];
+    const TRY_PY: &[&str] = &[
+        "python3.13",
+        "python3.12",
+        "python3.11",
+        "python3.10",
+        "python3.9",
+        "python3",
+        "python",
+        "python3.14",
+    ];
 
     let mut sys_py = None;
     let mut found = Vec::new();
@@ -357,22 +368,40 @@ fn create_venv_at_path(path: &Path) -> Result<(), Error> {
         return Err(ret);
     };
 
-    eprintln!("creating virtual environment at '{}' using '{sys_py}'", path.display());
-    let out = Command::new(sys_py).args(["-m", "virtualenv"]).arg(path).output().unwrap();
+    // First try venv, which should be packaged in the Python3 standard library.
+    // If it is not available, try to create the virtual environment using the
+    // virtualenv package.
+    if try_create_venv(sys_py, path, "venv").is_ok() {
+        return Ok(());
+    }
+    try_create_venv(sys_py, path, "virtualenv")
+}
+
+fn try_create_venv(python: &str, path: &Path, module: &str) -> Result<(), Error> {
+    eprintln!(
+        "creating virtual environment at '{}' using '{python}' and '{module}'",
+        path.display()
+    );
+    let out = Command::new(python).args(["-m", module]).arg(path).output().unwrap();
 
     if out.status.success() {
         return Ok(());
     }
 
     let stderr = String::from_utf8_lossy(&out.stderr);
-    let err = if stderr.contains("No module named virtualenv") {
+    let err = if stderr.contains(&format!("No module named {module}")) {
         Error::Generic(format!(
-            "virtualenv not found: you may need to install it \
-                               (`{sys_py} -m pip install virtualenv`)"
+            r#"{module} not found: you may need to install it:
+`{python} -m pip install {module}`
+If you see an error about "externally managed environment" when running the above command,
+either install `{module}` using your system package manager
+(e.g. `sudo apt-get install {python}-{module}`) or create a virtual environment manually, install
+`{module}` in it and then activate it before running tidy.
+"#
         ))
     } else {
         Error::Generic(format!(
-            "failed to create venv at '{}' using {sys_py}: {stderr}",
+            "failed to create venv at '{}' using {python} -m {module}: {stderr}",
             path.display()
         ))
     };