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Use windows registry to discover python
Our current strategy of parsing the output of `py --list-paths` to get the installed python versions on windows is brittle (#6524, missing `py`, etc.) and it's slow (10ms last time i measured). Instead, we should behave spec-compliant and read the python versions from the registry following PEP 514. We're using the official rust-for-windows crates for accessing the registry. Fixes #1521 Fixes #6524
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,93 +1,114 @@ | ||
| use regex::Regex; | ||
| use std::io; | ||
| use crate::PythonVersion; | ||
| use std::path::PathBuf; | ||
| use std::process::{Command, ExitStatus}; | ||
| use std::sync::LazyLock; | ||
| use thiserror::Error; | ||
| use tracing::info_span; | ||
| use std::str::FromStr; | ||
| use tracing::debug; | ||
| use windows_registry::{Key, Value, CURRENT_USER, LOCAL_MACHINE}; | ||
|
|
||
| /// A Python interpreter found in the Windows registry through PEP 514. | ||
| /// | ||
| /// There are a lot more (optional) fields defined in PEP 514, but we only care about path and | ||
| /// version here, for everything else we probe with a Python script. | ||
| #[derive(Debug, Clone)] | ||
| pub(crate) struct PyListPath { | ||
| pub(crate) major: u8, | ||
| pub(crate) minor: u8, | ||
| pub(crate) executable_path: PathBuf, | ||
| pub(crate) struct RegistryPython { | ||
| pub(crate) path: PathBuf, | ||
| pub(crate) version: Option<PythonVersion>, | ||
| } | ||
|
|
||
| /// An error was encountered when using the `py` launcher on Windows. | ||
| #[derive(Error, Debug)] | ||
| pub enum Error { | ||
| #[error("{message} with {exit_code}\n--- stdout:\n{stdout}\n--- stderr:\n{stderr}\n---")] | ||
| StatusCode { | ||
| message: String, | ||
| exit_code: ExitStatus, | ||
| stdout: String, | ||
| stderr: String, | ||
| }, | ||
| #[error("Failed to run `py --list-paths` to find Python installations")] | ||
| Io(#[source] io::Error), | ||
| #[error("The `py` launcher could not be found")] | ||
| NotFound, | ||
| /// Àdding `windows_registry::Value::into_string()`. | ||
| fn value_to_string(value: Value) -> Option<String> { | ||
| match value { | ||
| Value::String(string) => Some(string), | ||
| Value::Bytes(bytes) => String::from_utf8(bytes.to_vec()).ok(), | ||
| Value::U32(_) | Value::U64(_) | Value::MultiString(_) | Value::Unknown(_) => None, | ||
| } | ||
| } | ||
|
|
||
| /// ```text | ||
| /// -V:3.12 C:\Users\Ferris\AppData\Local\Programs\Python\Python312\python.exe | ||
| /// -V:3.8 C:\Users\Ferris\AppData\Local\Programs\Python\Python38\python.exe | ||
| /// ``` | ||
| static PY_LIST_PATHS: LazyLock<Regex> = LazyLock::new(|| { | ||
| // Without the `R` flag, paths have trailing \r | ||
| Regex::new(r"(?mR)^ -(?:V:)?(\d).(\d+)-?(?:arm)?\d*\s*\*?\s*(.*)$").unwrap() | ||
| }); | ||
|
|
||
| /// Use the `py` launcher to find installed Python versions. | ||
| /// | ||
| /// Calls `py --list-paths`. | ||
| pub(crate) fn py_list_paths() -> Result<Vec<PyListPath>, Error> { | ||
| // konstin: The command takes 8ms on my machine. | ||
| let output = info_span!("py_list_paths") | ||
| .in_scope(|| Command::new("py").arg("--list-paths").output()) | ||
| .map_err(|err| { | ||
| if err.kind() == std::io::ErrorKind::NotFound { | ||
| Error::NotFound | ||
| } else { | ||
| Error::Io(err) | ||
| /// Find all Pythons registered in the Windows registry following PEP 514. | ||
| pub(crate) fn registry_pythons() -> Result<Vec<RegistryPython>, windows_result::Error> { | ||
| let mut registry_pythons = Vec::new(); | ||
| for root_key in [CURRENT_USER, LOCAL_MACHINE] { | ||
| let Ok(key_python) = root_key.open(r"Software\Python") else { | ||
| continue; | ||
| }; | ||
| for company in key_python.keys()? { | ||
| // Reserved name according to the PEP. | ||
| if company == "PyLauncher" { | ||
| continue; | ||
| } | ||
| })?; | ||
| let Ok(company_key) = key_python.open(&company) else { | ||
| // Ignore invalid entries | ||
| continue; | ||
| }; | ||
| for tag in company_key.keys()? { | ||
| let tag_key = company_key.open(&tag)?; | ||
|
|
||
| // `py` sometimes prints "Installed Pythons found by py Launcher for Windows" to stderr which we ignore. | ||
| if !output.status.success() { | ||
| return Err(Error::StatusCode { | ||
| message: format!( | ||
| "Running `py --list-paths` failed with status {}", | ||
| output.status | ||
| ), | ||
| exit_code: output.status, | ||
| stdout: String::from_utf8_lossy(&output.stdout).trim().to_string(), | ||
| stderr: String::from_utf8_lossy(&output.stderr).trim().to_string(), | ||
| }); | ||
| if let Some(registry_python) = read_registry_entry(&company, &tag, &tag_key) { | ||
| registry_pythons.push(registry_python); | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // Find the first python of the version we want in the list | ||
| let stdout = String::from_utf8(output.stdout).map_err(|err| Error::StatusCode { | ||
| message: format!("The stdout of `py --list-paths` isn't UTF-8 encoded: {err}"), | ||
| exit_code: output.status, | ||
| stdout: String::from_utf8_lossy(err.as_bytes()).trim().to_string(), | ||
| stderr: String::from_utf8_lossy(&output.stderr).trim().to_string(), | ||
| })?; | ||
| // The registry has no natural ordering, so we're processing the latest version first. | ||
| registry_pythons.sort_by(|a, b| { | ||
| // Highest version first (reverse), but missing versions at the bottom (regular order). | ||
| if let (Some(version_a), Some(version_b)) = (&a.version, &b.version) { | ||
| version_a | ||
| .cmp(&version_b) | ||
| .reverse() | ||
| .then(a.path.cmp(&b.path)) | ||
| } else { | ||
| a.version | ||
| .as_ref() | ||
| .map(|version| &***version) | ||
| .cmp(&b.version.as_ref().map(|version| &***version)) | ||
| .then(a.path.cmp(&b.path)) | ||
| } | ||
| }); | ||
|
|
||
| Ok(PY_LIST_PATHS | ||
| .captures_iter(&stdout) | ||
| .filter_map(|captures| { | ||
| let (_, [major, minor, path]) = captures.extract(); | ||
| if let (Some(major), Some(minor)) = (major.parse::<u8>().ok(), minor.parse::<u8>().ok()) | ||
| { | ||
| Some(PyListPath { | ||
| major, | ||
| minor, | ||
| executable_path: PathBuf::from(path), | ||
| }) | ||
| } else { | ||
| Ok(registry_pythons) | ||
| } | ||
|
|
||
| fn read_registry_entry(company: &str, tag: &str, tag_key: &Key) -> Option<RegistryPython> { | ||
| // `ExecutablePath` is mandatory for executable Pythons. | ||
| let Some(executable_path) = tag_key | ||
| .open("InstallPath") | ||
| .and_then(|install_path| install_path.get_value("ExecutablePath")) | ||
| .ok() | ||
| .and_then(value_to_string) | ||
| else { | ||
| debug!( | ||
| r"Registry Python is not executable: `Software\Python\{}\{}", | ||
| company, tag | ||
| ); | ||
| return None; | ||
| }; | ||
| debug!( | ||
| "Found registry Python {} {}: `{}`", | ||
| company, tag, executable_path | ||
| ); | ||
|
|
||
| // `SysVersion` is optional. | ||
| let version = tag_key | ||
| .get_value("SysVersion") | ||
| .ok() | ||
| .and_then(|value| match value { | ||
| Value::String(s) => Some(s), | ||
| _ => None, | ||
| }) | ||
| .and_then(|s| match PythonVersion::from_str(&s) { | ||
| Ok(version) => Some(version), | ||
| Err(err) => { | ||
| debug!( | ||
| "Invalid registry Python version at {}: {}", | ||
| executable_path, err | ||
| ); | ||
| None | ||
| } | ||
| }) | ||
| .collect()) | ||
| }); | ||
|
|
||
| Some(RegistryPython { | ||
| path: PathBuf::from(executable_path), | ||
| version, | ||
| }) | ||
| } |