73 lines
2.6 KiB
JavaScript
73 lines
2.6 KiB
JavaScript
/**
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* Cross-platform Python interpreter resolver.
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*
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* Provides utilities to detect the available Python interpreter on the current
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* system and to normalize shell commands that reference `python`/`python3` so
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* that they use whichever interpreter is actually installed.
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*
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* On Windows the canonical names differ (`py -3`, `python`, `python3`), so
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* hard-coded `python3` invocations fail with exit 127. This module detects the
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* working interpreter once (cached for the process lifetime) and rewrites
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* commands accordingly.
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*
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* @module python-resolver
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*/
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import { spawnSync } from "node:child_process";
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/** Cached result of `detectPythonExecutable`. `undefined` means not yet probed. */
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let cached;
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/**
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* Returns the first working Python invocation on this system, or `null` if no
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* Python interpreter is found.
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*
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* Probe order:
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* - Windows: `py -3` → `python` → `python3`
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* - All other platforms: `python3` → `python`
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*
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* The result is cached for the lifetime of the process to avoid repeated
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* `spawnSync` calls.
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*/
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export function detectPythonExecutable() {
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if (cached !== undefined) return cached;
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const candidates =
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process.platform === "win32"
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? ["py -3", "python", "python3"]
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: ["python3", "python"];
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for (const candidate of candidates) {
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const [bin, ...args] = candidate.split(" ");
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const r = spawnSync(bin, [...args, "--version"], { stdio: "ignore" });
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if (!r.error && r.status === 0) {
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cached = candidate;
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return candidate;
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}
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}
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cached = null;
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return null;
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}
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/**
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* Rewrites a shell command string so that leading `python`/`python3`/`py`
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* tokens at command boundaries are replaced with the interpreter returned by
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* `detectPythonExecutable`.
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*
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* Only tokens at command boundaries (start of string, or after `&&`, `||`,
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* `;`) are rewritten — mid-string occurrences (e.g. file paths containing
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* "python") are left intact.
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*
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* When no Python interpreter is detected, the command is returned unchanged so
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* that the caller receives a meaningful "command not found" error rather than a
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* silent no-op.
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*
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* @param command - The shell command string to normalize.
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* @returns The command with Python interpreter tokens rewritten, or the
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* original command if no rewrite is needed.
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*/
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export function normalizePythonCommand(command) {
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const executable = detectPythonExecutable();
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if (!executable) return command;
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// Split on common shell separators to handle compound commands.
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// We reconstruct the string preserving the original separators.
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return command.replace(
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/(^\s*|(?:&&|\|\||;)\s*)(?:python3?|py(?:\s+-\d+)?)(?=\s|$)/g,
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(_match, pre) => `${pre}${executable}`,
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);
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}
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