socket_patch_core/utils/
process.rs

1//! Subprocess invocation seam shared by the ecosystem crawlers.
2//!
3//! Several crawlers ask an external CLI for a path that's hard to
4//! infer otherwise — `npm root -g`, `gem env gemdir`, `python3 -c
5//! "import site; ..."`, etc. The historical pattern was to embed
6//! `std::process::Command::new(bin).args([...]).output()` directly
7//! inside each helper, which leaves two arms untestable without
8//! installing the binary: the success arm (binary present, stdout
9//! parsed) and the spawn-Err arm (binary missing or unspawnable).
10//!
11//! This module provides a `CommandRunner` trait whose default impl,
12//! `SystemCommandRunner`, performs the real spawn, and whose test
13//! double (`MockCommandRunner` in `tests/common/mod.rs`) maps
14//! `(bin, args)` to canned stdout. Each shell-out helper accepts a
15//! `&dyn CommandRunner` argument so tests can inject the mock;
16//! production callers either build the helper with the default
17//! runner or thread a singleton.
18
19use std::process::{Command, Stdio};
20
21/// Run an external binary with the given args and return its
22/// stdout, trimmed, when the spawn succeeded AND the process exited
23/// with a success status AND stdout is non-empty after trimming.
24///
25/// Returns `None` for any of: spawn failure (binary not on PATH),
26/// non-zero exit status, empty stdout after trim. Stderr is
27/// captured and discarded — the crawlers treat all failures as
28/// "no information", not as errors to surface.
29pub trait CommandRunner: Send + Sync {
30    fn run(&self, bin: &str, args: &[&str]) -> Option<String>;
31}
32
33/// Default runner: spawns the real binary via `std::process::Command`.
34///
35/// Stdin is set to /dev/null so the child can't block waiting for
36/// input. stdout is captured; stderr is captured and dropped (we
37/// don't surface CLI diagnostics — the helpers fall back to other
38/// discovery paths on any failure).
39pub struct SystemCommandRunner;
40
41impl CommandRunner for SystemCommandRunner {
42    fn run(&self, bin: &str, args: &[&str]) -> Option<String> {
43        let output = Command::new(bin)
44            .args(args)
45            .stdin(Stdio::null())
46            .stdout(Stdio::piped())
47            .stderr(Stdio::piped())
48            .output()
49            .ok()?;
50        if !output.status.success() {
51            return None;
52        }
53        let stdout = String::from_utf8_lossy(&output.stdout).trim().to_string();
54        if stdout.is_empty() {
55            None
56        } else {
57            Some(stdout)
58        }
59    }
60}
61
62#[cfg(test)]
63mod tests {
64    use super::*;
65
66    /// Confirm the real runner returns Some for a tiny command we
67    /// know is on every Unix PATH — `echo`. Skipped on Windows where
68    /// `echo` isn't a real binary.
69    #[cfg(unix)]
70    #[test]
71    fn system_runner_returns_stdout_for_real_binary() {
72        let runner = SystemCommandRunner;
73        let out = runner.run("echo", &["hello"]).expect("echo should succeed");
74        assert_eq!(out, "hello");
75    }
76
77    /// Spawn failure → None. The binary name is intentionally one
78    /// that should never be on PATH.
79    #[test]
80    fn system_runner_returns_none_on_spawn_failure() {
81        let runner = SystemCommandRunner;
82        let out = runner.run("definitely-not-a-real-binary-1234567", &[]);
83        assert_eq!(out, None);
84    }
85
86    /// Non-zero exit → None. `false`(1) is in coreutils everywhere.
87    #[cfg(unix)]
88    #[test]
89    fn system_runner_returns_none_on_non_zero_exit() {
90        let runner = SystemCommandRunner;
91        let out = runner.run("false", &[]);
92        assert_eq!(out, None);
93    }
94}
socket_patch_core/utils/process.rs

socket_patch_core/utils/
process.rs
