Can expectrl spawn with modified environment variables?

[Centauria]

Let's say this code

let mut session = expectrl::repl::spawn_python();

I need it find python in somewhere else beyond system PATH,
so I add something like

if let Some(path) = env::var_os("PATH") {
        let mut paths = env::split_paths(&path).collect::<Vec<_>>();
        paths.push(PathBuf::from(r"D:\PF\anaconda3\envs\forecast"));
        paths.push(PathBuf::from(r"C:\Users\centa\.julia\juliaup\julia-1.10.2+0.x64.w64.mingw32\bin"));
        let new_path = env::join_paths(paths).unwrap();
        env::set_var("PATH", &new_path);
    }

before that.

But this won't work.

So is there an approach for doing this?

[zhiburt]

Hi @Centauria

Something like this?

use expectrl::{Expect, Regex};

fn main() {
    let path_to_python_bin = "/usr/bin/python";

    let mut p = expectrl::spawn(path_to_python_bin).unwrap();
    p.expect(Regex("\n")).unwrap(); // skip python prompt

    p.send_line("print('Does it work?')").unwrap();

    let mut buf = String::new();
    p.read_line(&mut buf).unwrap();

    assert_eq!(buf, ">>> Does it work?\r\n");
}

Or like this

fn main() {
    let path_to_python_bin = "/usr/bin/python";

    let p = expectrl::spawn(path_to_python_bin).unwrap();
    let mut p = expectrl::repl::ReplSession::new(p, ">>> ");
    p.set_quit_command("quit()");
    p.expect_prompt().unwrap();

    p.send_line("print('Does it work?')").unwrap();

    let mut buf = String::new();
    p.read_line(&mut buf).unwrap();

    assert_eq!(buf, "Does it work?\r\n");
}

[Centauria]

Thank you for the fast reply.
I tried your approach and it worked.
That's to say, I can only specify path to python executable, then spawn it.

But what should I do if I need the spawned python recognize some specific environment variables, such as "PYTHONPATH", for further usage?

[zhiburt]

Well the example you've provided
Must work, doesn't it?

use std::env;
use std::path::PathBuf;

fn main() {
    set_env("SOMEWHERE_NEW");

    let p = expectrl::spawn("python").unwrap();
    let mut p = expectrl::repl::ReplSession::new(p, ">>> ");
    p.set_quit_command("quit()");
    p.expect_prompt().unwrap();

    let output = p.execute("import os; print(os.environ.get('PATH'))").unwrap();

    println!("{}", String::from_utf8_lossy(&output));
}

fn set_env(p: &str) {
    if let Some(path) = env::var_os("PATH") {
        let mut paths = env::split_paths(&path).collect::<Vec<_>>();
        paths.push(PathBuf::from(p));
        let new_path = env::join_paths(paths).unwrap();
        env::set_var("PATH", new_path);
    }
}

You could also use std::process::Command for it.

use std::process::Command;

use expectrl::Session;

fn main() {
    let mut cmd = Command::new("python");
    cmd.env("SOME_NEW_ENV", "NEW VALUE");

    let p = Session::spawn(cmd).unwrap();
    let mut p = expectrl::repl::ReplSession::new(p, ">>> ");
    p.set_quit_command("quit()");
    p.expect_prompt().unwrap();

    let output = p
        .execute("import os; print(os.environ.get('SOME_NEW_ENV'))")
        .unwrap();

    println!("{}", String::from_utf8_lossy(&output));
}

[Centauria]

The first code snippet do not work.
Even though it changes the "PATH" variable in the code, e.g. env::var_os("PATH") changes, expectrl::spawn("python") still cannot find python in the "PATH".

The second code snippet do not work.

I changed it like below:

use std::process::Command;

use expectrl::repl::ReplSession;
use expectrl::Session;

fn main() {
    let mut cmd = Command::new(r"D:\path\to\anaconda3\python.exe");
    cmd.env("SOME_NEW_ENV", "NEW VALUE");

    let p = Session::spawn(cmd).unwrap();
    let mut p = ReplSession::new(
        p,
        ">>> ".to_owned(),
        Some("import sys; sys.exit()".to_owned()),
        false,
    );
    p.expect_prompt().unwrap();

    let output = p
        .execute("import os; print(os.environ.get('SOME_NEW_ENV'))")
        .unwrap();

    println!("{}", String::from_utf8_lossy(&output));
}

this code do not work on Windows.

thread 'main' panicked at src/main.rs:17:23:
called `Result::unwrap()` on an `Err` value: ExpectTimeout
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
error: process didn't exit successfully: `target\debug\exptest.exe` (exit code: 101)

I changed ">>> " to ">>>", then it can run on Windows. But the result is different between different Windows version.

On Windows 10, 19045.4651, it prints a blank line

on Windows 11, 22631.3880, it prints

 import os; print(os.environ.get('SOME_NEW_ENV'))
NEW VALUE

rustup show result

Default host: x86_64-pc-windows-msvc
rustup home:  D:\PF\Rust\Rustup

stable-x86_64-pc-windows-msvc (default)
rustc 1.79.0 (129f3b996 2024-06-10)