Request: Add a crate_feature to disable macros that depend on cargo env vars #783
Comments
|
Wow, I wasn't aware of Bazel, that's interesting. Although I'm not against adding these to a feature, and simply adding said feature to the defaults but I do worry that there are people who have opted out of Because of that concern, I think the best way forward is to add this to the 3x timeline, which hopefully isn't too far off (waiting on Macros 1.1). I believe all you should have to do on your end is export those environmental variables while building, and it should work? |
kbknapp
added
C: macros
M-breaking-change
|
No worries, thanks for the quick response! Exporting fake values during my build step solves my problem and is no trouble for any length of time. |
Valid, but unnecessary concern. Consider: [features]
no_cargo = []Then: #[cfg(not(feature="no_cargo"))]
macro_rules! crate_authors {
// magic
}That way you need an explicit opt-in to remove the macros, granting full backwards compatibility |
Add no_cargo feature to disable Cargo-env-var-dependent macros
For example, given:
```toml
clap = { path = "t:/clap-rs" }
```
The macros `crate_version!()` and `crate_authors!()` exist, so the crate compiles without errors:
```
Compiling https v0.2.0 (file:///P:/Rust/http)
Finished debug [unoptimized + debuginfo] target(s) in 6.93 secs
Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
[Finished in 7.5s]
```
But, adding the `no_cargo` feature:
```toml
clap = { path = "t:/clap-rs", features = ["no_cargo"] }
```
The macros are removed, so the crate fails to compile:
```
Compiling clap v2.19.2 (file:///T:/clap-rs)
Compiling https v0.2.0 (file:///P:/Rust/http)
error: macro undefined: 'crate_version!'
--> src\options.rs:40:22
|
40 | .version(crate_version!())
| ^^^^^^^^^^^^^
error: macro undefined: 'crate_authors!'
--> src\options.rs:41:21
|
41 | .author(crate_authors!())
| ^^^^^^^^^^^^^
error: aborting due to 2 previous errors
error: Could not compile `https`.
```
Closes #783
Add no_cargo feature to disable Cargo-env-var-dependent macros
For example, given:
```toml
clap = { path = "t:/clap-rs" }
```
The macros `crate_version!()` and `crate_authors!()` exist, so the crate compiles without errors:
```
Compiling https v0.2.0 (file:///P:/Rust/http)
Finished debug [unoptimized + debuginfo] target(s) in 6.93 secs
Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
[Finished in 7.5s]
```
But, adding the `no_cargo` feature:
```toml
clap = { path = "t:/clap-rs", features = ["no_cargo"] }
```
The macros are removed, so the crate fails to compile:
```
Compiling clap v2.19.2 (file:///T:/clap-rs)
Compiling https v0.2.0 (file:///P:/Rust/http)
error: macro undefined: 'crate_version!'
--> src\options.rs:40:22
|
40 | .version(crate_version!())
| ^^^^^^^^^^^^^
error: macro undefined: 'crate_authors!'
--> src\options.rs:41:21
|
41 | .author(crate_authors!())
| ^^^^^^^^^^^^^
error: aborting due to 2 previous errors
error: Could not compile `https`.
```
Closes #783
|
This might cover the same territory: rust-lang/rust#39656 |
The crate_*! macros make a fairly valid assumption that consumers use
cargoto build Rust projects by expecting certain environment variables to be present. Unfortunately, I am one of the very few not usingCargo. I'm actually experimenting with Bazel to build my Rust projects -- butclapfails to compile because bazel is not providing the expected environment variables.As of posting, the macros causing me issues are "crate_version!" and "crate_authors!", which seem to be provided as a convenience to
clapusers and aren't used internally.If this proposal is rejected, I do have mitigation options -- faking those values or patching clap locally -- so please reject if you feel that not enough users are impacted.
Thanks!
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