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Add support for --env on tracked_env::var #118830

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merged 3 commits into from
Dec 17, 2023
Merged

Add support for --env on tracked_env::var #118830

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6ce2fef
Add support for `--env` on `tracked_env::var`
GuillaumeGomez Dec 11, 2023
5967ceb
Update rust-analyzer to support new `injected_env_var` function
GuillaumeGomez Dec 11, 2023
453ff1e
Add tests for `--env` usage with `tracked_env::var`
GuillaumeGomez Dec 11, 2023
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4 changes: 4 additions & 0 deletions compiler/rustc_expand/src/proc_macro_server.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -426,6 +426,10 @@ impl server::Types for Rustc<'_, '_> {
}

impl server::FreeFunctions for Rustc<'_, '_> {
fn injected_env_var(&mut self, var: &str) -> Option<String> {
self.ecx.sess.opts.logical_env.get(var).cloned()
}

fn track_env_var(&mut self, var: &str, value: Option<&str>) {
self.sess()
.env_depinfo
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1 change: 1 addition & 0 deletions library/proc_macro/src/bridge/mod.rs
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Expand Up @@ -55,6 +55,7 @@ macro_rules! with_api {
$m! {
FreeFunctions {
fn drop($self: $S::FreeFunctions);
fn injected_env_var(var: &str) -> Option<String>;
fn track_env_var(var: &str, value: Option<&str>);
fn track_path(path: &str);
fn literal_from_str(s: &str) -> Result<Literal<$S::Span, $S::Symbol>, ()>;
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3 changes: 2 additions & 1 deletion library/proc_macro/src/lib.rs
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Expand Up @@ -1503,7 +1503,8 @@ pub mod tracked_env {
#[unstable(feature = "proc_macro_tracked_env", issue = "99515")]
pub fn var<K: AsRef<OsStr> + AsRef<str>>(key: K) -> Result<String, VarError> {
let key: &str = key.as_ref();
let value = env::var(key);
let value = crate::bridge::client::FreeFunctions::injected_env_var(key)
.map_or_else(|| env::var(key), Ok);
crate::bridge::client::FreeFunctions::track_env_var(key, value.as_deref().ok());
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@Noratrieb Noratrieb Dec 11, 2023 •
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Is it correct to track --env here? I don't think it is. Tracked env vars end up in depinfo, implying that the compiler invocation depended on this environment variable, but it didn't, there is no environment variable and even if there is, the compiler didn't care, it just depended on a flag. I think it should only track when env::var is used.

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Well, if this function is called, it means the environment variable was used no? Or did I misunderstand what you meant?

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@Noratrieb Noratrieb Dec 11, 2023 •
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From an outside perspective, no "environment variable" was used. It just took a value for the flag. A build system doesn't have to check whether an environment variables changes to figure out whether a rebuild is needed, it needs to look at arguments instead (which it of course already does).

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Well, I'm fine with removing this call to track_env_var. Please just confirm it's what you want I do do it. :)

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@Noratrieb Noratrieb Dec 11, 2023 •
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Yes
I also just checked your previous PR and I missed that there:
https://github.com/rust-lang/rust/pull/118368/files#diff-0eaa1095d59f2f3d9c015005d15fd8f7cda13121a8404d77b2955fc5fcd40449R37

The name here also makes it more clear what tracking is for: it's for depinfo which is used by builds systems or other consumers to figure out what went into the compilation (for example when things need to be rebuilt). It's essential that rustc records env variables it reads with env::var. But --env are not actually env variables in the build environment, so they don't need to be tracked. I'd also be happy to review a PR changing the behavior for the macros to not track when the var is read from --env>

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That's a flag though and not an environment variable. A build system already needs to handle flags changing. Depinfo tells the build system "hey, I read this environment variable, check it again next time" but in reality it didn't read any environment variable, it got it from the flag.

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If it is not tracked in the dep info, any change to a --env argument would need to trigger recompilation of all crates even if they don't use those env!() at all.

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I see, for build systems that pass env vars explicitly like that it would be nice if they could detect whether it was actually used. But I don't think the normal env depinfo is the right place for that. The case I was thinking about was for example having A=x in the environment and using --env A=x. Then, changing A=y should not cause any rebuilds as it wasn't used, only the --env A=x value was.

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The case I was thinking about was for example having A=x in the environment and using --env A=x. Then, changing A=y should not cause any rebuilds as it wasn't used, only the --env A=x value was.

And in this case it won't trigger a rebuild because the value is same. The --env option uses the same mechanism as the env! macro: variables are tracked if used and will trigger a rebuild if their value changed. So unless I missed something, I think it's doing exactly what we want?

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So we're relying on build systems correctly doing the "dep info env -> when I passed --env" translation themselves, since they know they passed the flag.
That makes sense, I didn't think of that, I was too focused on the env depinfo meaning actual environment variable, but I guess the build system is supposed to know what it's doing.
In that case, sounds good. Maybe it should be documented explicitly in the documentation for --env that it ends up in depinfo as env vars.

value
}
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4 changes: 4 additions & 0 deletions src/tools/rust-analyzer/crates/proc-macro-srv/src/server.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,10 @@ impl server::Types for RustAnalyzer {
}

impl server::FreeFunctions for RustAnalyzer {
fn injected_env_var(&mut self, _var: &str) -> Option<String> {
None
}

fn track_env_var(&mut self, _var: &str, _value: Option<&str>) {
// FIXME: track env var accesses
// https://github.com/rust-lang/rust/pull/71858
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28 changes: 28 additions & 0 deletions tests/ui/proc-macro/auxiliary/env.rs
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@@ -0,0 +1,28 @@
// force-host
// no-prefer-dynamic

#![crate_type = "proc-macro"]
#![feature(proc_macro_tracked_env)]

extern crate proc_macro;

use proc_macro::TokenStream;
use proc_macro::tracked_env::var;

#[proc_macro]
pub fn generate_const(input: TokenStream) -> TokenStream {
let the_const = match var("THE_CONST") {
Ok(x) if x == "12" => {
"const THE_CONST: u32 = 12;"
}
_ => {
"const THE_CONST: u32 = 0;"
}
};
let another = if var("ANOTHER").is_ok() {
"const ANOTHER: u32 = 1;"
} else {
"const ANOTHER: u32 = 2;"
};
format!("{the_const}{another}").parse().unwrap()
}
17 changes: 17 additions & 0 deletions tests/ui/proc-macro/env.rs
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@@ -0,0 +1,17 @@
// aux-build:env.rs
// run-pass
// rustc-env: THE_CONST=1
// compile-flags: -Zunstable-options --env THE_CONST=12 --env ANOTHER=4

#![crate_name = "foo"]

extern crate env;

use env::generate_const;

generate_const!();

fn main() {
assert_eq!(THE_CONST, 12);
assert_eq!(ANOTHER, 1);
}
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