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## Background In virtual environments, we want to install python programs as console commands, e.g. `black .` over `python -m black .`. They may be called [entrypoints](https://packaging.python.org/en/latest/specifications/entry-points/) or scripts. For entrypoints, we're given a module name and function to call in that module. On Unix, we generate a minimal python script launcher. Text files are runnable on unix by adding a shebang at their top, e.g. ```python #!/usr/bin/env python ``` will make the operating system run the file with the current python interpreter. A venv launcher for black in `/home/ferris/colorize/.venv` (module name: `black`, function to call: `patched_main`) would look like this: ```python #!/home/ferris/colorize/.venv/bin/python # -*- coding: utf-8 -*- import re import sys from black import patched_main if __name__ == "__main__": sys.argv[0] = re.sub(r"(-script\.pyw|\.exe)?$", "", sys.argv[0]) sys.exit(patched_main()) ``` On windows, this doesn't work, we can only rely on launching `.exe` files. ## Summary We use posy's rust implementation of a trampoline, which is based on distlib's c++ implementation. We pre-build a minimal exe and append the launcher script as stored zip archive behind it. The exe will look for the venv python interpreter next to it and use it to execute the appended script. The changes in this PR make the `black` entrypoint work: ```powershell cargo run -- venv .venv cargo run -q -- pip install black .\.venv\Scripts\black --version ``` Integration with our existing tests will be done in follow-up PRs. ## Implementation and Details I've vendored the posy trampoline crate. It is a formatted, renamed and slightly changed for embedding version of https://github.com/njsmith/posy/pull/28. The posy launchers are smaller than the distlib launchers, 16K vs 106K for black. Currently only `x86_64-pc-windows-msvc` is supported. The crate requires a nightly compiler for its no-std binary size tricks. On windows, an application can be launched with a console or without (to create windows instead), which needs two different launchers. The gui launcher will subsequently use `pythonw.exe` while the console launcher uses `python.exe`.
16 lines
744 B
Rust
16 lines
744 B
Rust
// This embeds a "manifest" - a special XML document - into our built binary.
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// The main things it does is tell Windows that we want to use the magic
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// utf8 codepage, so we can use the *A versions of Windows API functions and
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// don't have to mess with utf-16.
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use embed_manifest::{embed_manifest, new_manifest};
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fn main() {
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if std::env::var_os("CARGO_CFG_WINDOWS").is_some() {
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let manifest = new_manifest("Puffin.Trampoline")
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.remove_dependency("Microsoft.Windows.Common-Controls");
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embed_manifest(manifest).expect("unable to embed manifest");
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println!("cargo:rustc-link-arg=/ENTRY:entry");
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println!("cargo:rustc-link-arg=/LTCG");
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println!("cargo:rerun-if-changed=build.rs");
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}
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}
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