How can I force `build.rs` to run again without cleaning my whole project?

问题

How can I force build.rs to run again without cleaning my whole project? I checked cargo build --help but I couldn't find anything related to build.rs.

回答1:

If you print

"cargo:rerun-if-changed=<FILE>"

the build will be triggered every time the file has changed.

rerun-if-changed=PATH is a path to a file or directory which indicates that the build script should be re-run if it changes (detected by a more-recent last-modified timestamp on the file). Normally build scripts are re-run if any file inside the crate root changes, but this can be used to scope changes to just a small set of files. -- source

I'm not aware of a solution without changing a file manually (I just put a whitespace anywhere in my build.rs, it will be removed by rustfmt though).

I have several buildscripts in my projects, and mostly these two lines give me a nice solution:

println!("cargo:rerun-if-changed=build.rs");
println!("cargo:rerun-if-changed=path/to/Cargo.lock");

but I guess you are looking for a command rustc/cargo command. Anyway, you can put in a small script, which will edit a certain file, which will trigger the build-process.

回答2:

If build.rs changes, Cargo already rebuilds the project:

Note that if the build script itself (or one of its dependencies) changes, then it's rebuilt and rerun unconditionally, so cargo:rerun-if-changed=build.rs is almost always redundant (unless you want to ignore changes in all other files except for build.rs). doc

On Linux, I will just do touch build.rs && cargo build. For Windows, see Windows equivalent of the Linux command 'touch'?

回答3:

Register `build.rs` as a crate's `bin` target:

Add this to your Cargo.toml file:

[package]
edition = "2018"
build = "build.rs"

[[bin]]
name = "force-build"
path = "build.rs"
required-features = ["build_deps"]  # only needed for build-dependencies

If you have any [build-dependencies] (e.g. some_crate = "1.2.3"), you need to add those to (the main) [dependencies] (sadly no [bin-dependencies] as of yet), but you can make them optional:
```
[dependencies]
some_crate = { version = "1.2.3", optional = true }

[features]
build_deps = ["some_crate"]
```

Then you can run the build script with:

$ cargo run --bin force-build --features build_deps

(or $ cargo run --bin force-build when no [build-dependencies])

You can even disable the automatic call of the build script by replacing the build = "build.rs" line in Cargo.toml with build = false
Note: since the OUT_DIR env var is not present for bin targets, if your build.rs script uses env!("OUT_DIR"), you may "fix this" by using concat!(env!("CARGO_MANIFEST_DIR"), "/target/") instead.

回答4:

If you got target under gitignore (which you should) this might be useful for any file changes when you're developing and testing the build script.

if Path::new(".git/HEAD").exists() {
    println!("cargo:rerun-if-changed=.git/HEAD");
}

回答5:

I can offer the solution that works for me well.

Add the following to build.rs file to a dependency that have to be rebuilt everytime:

use failure::{format_err, Error};
use std::env;
use std::path::PathBuf;
use std::process::Command;

/// Just useful trait to run a command
trait RunIt {
    fn run_it(&mut self, err: &str) -> Result<(), Error>;
}

impl RunIt for Command {
    fn run_it(&mut self, err: &str) -> Result<(), Error> {
        let output = self.output()?;
        if !output.status.success() {
            let out = String::from_utf8_lossy(&output.stderr);
            eprintln!("{}", out);
            Err(format_err!("{}", err))
        } else {
            Ok(())
        }
    }
}

fn main() -> Result<(), Error> {

    // Your build stuff

    // Activate this feature to rebuild this dependency everytime
    if cfg!(feature = "refresh") {
        Command::new("touch")
            .args(&["build.rs"])
            .run_it("Can't touch the build file")?;
    }

    Ok(())
}

Add the feature to Cargo.toml to declare the feature:

[package]
name = "sensitive-crate"

[features]
default = []
refresh = []

And activate refresh feature to rebuild the dependency everytime:

[package]
name = "my_project_1"

[dependencies]
sensitive-crate = { path = "../sensitive-crate", features = ["refresh"] }

来源：https://stackoverflow.com/questions/49077147/how-can-i-force-build-rs-to-run-again-without-cleaning-my-whole-project

标签

rust

rust-cargo