This implements the repo_mapping capabilities and provides a new
runfiles API. The new API can be accessed explicitly as
`runfiles::Runfiles::rlocation_from` or with the `runfiles::rlocation!`
macro, which adds compile-time support for correctly embedding the
external repo. This is a purely new API, existing usage continues to
work, although we mark it deprecated because it's not fully correct. We
can remove it at some point in the future.

This PR also transitions in-repo examples/tests to using it, in case
anyone copies them.

---------

Co-authored-by: scentini <[email protected]>

This helps keep my bazelrc cleaner since I can pass clippy flags on
multiple lines with comments about why they're being added.

Co-authored-by: Daniel Wagner-Hall <[email protected]>

Otherwise wasm_bindgen with rules_js is unusable.

See bazelbuild/bazel#22024 for details.

Co-authored-by: Daniel Wagner-Hall <[email protected]>

Co-authored-by: UebelAndre <[email protected]>

…ros (#2630)

This updates the bootstrap repository rule to use the same interface the
dependency macros and crate_universe does:
-
https://github.com/bazelbuild/rules_rust/blob/0.42.1/rust/repositories.bzl#L157-L158
-
https://github.com/bazelbuild/rules_rust/blob/0.42.1/crate_universe/private/crates_repository.bzl#L302-L305

This adds the following new logging when `CARGO_BAZEL_DEBUG=1` is
enabled in the environment when the repository rule runs.
```
cd test/no_std && CARGO_BAZEL_REPIN=1 CARGO_BAZEL_DEBUG=1 bazel sync --only=no_std_crate_index
```
````
...
...
Splice 2024-04-27T16:31:48.249675Z DEBUG write_registry_urls_and_feature_map: cargo_bazel::splicing::splicer: Writing Cargo manifest '/private/var/tmp/_bazel_user/427c86c43c8db37f50959419e7306f4e/external/no_std_crate_index/splicing-workspace/Cargo.toml':
```toml
[dependencies.libc_alloc]
version = "1.0.3"

[lib]
name = "direct_cargo_bazel_deps"
path = ".direct_cargo_bazel_deps.rs"
required-features = []

[package]
edition = "2018"
name = "direct-cargo-bazel-deps"
version = "0.0.1"

[workspace]
members = []
resolver = "2"

[workspace.metadata.cargo-bazel.features."direct-cargo-bazel-deps
0.0.1"]
common = []

[workspace.metadata.cargo-bazel.features."direct-cargo-bazel-deps
0.0.1".selects]

[workspace.metadata.cargo-bazel.features."libc_alloc 1.0.4"]
common = []

[workspace.metadata.cargo-bazel.features."libc_alloc 1.0.4".selects]

[workspace.metadata.cargo-bazel.package_prefixes]

[workspace.metadata.cargo-bazel.sources."libc_alloc 1.0.4"]
sha256 =
"6a090348b66d90d8507e30f0d2bd88e5a5c454bd1733fc6d617cbc3471bf69ea"
url = "https://static.crates.io/crates/libc_alloc/1.0.4/download"
```
...
...
````

I build in a hermetic c++ toolchain and use `-isystem` args in addition
to `-sysroot` which did not get rewritten before.

this is one of the errors I get (indirect dependency when using
`aspect_rules_py`):
```
cargo:warning=ToolExecError: Command "/tmp/bazel-working-directory/_main/external/local_config_cc/bin/clang" ... "-nostdinc" "-isystem" "external/local_config_cc/cxxlib/fastbuild/include/clang" "-isystem" "external/local_config_cc/cxxlib/fastbuild/include/x86_64-linux-gnu" "-isystem" "external/local_config_cc/cxxlib/fastbuild/include" "--sysroot=/tmp/bazel-working-directory/_main/external/local_config_cc/cxxlib/fastbuild" ... "-o" "/tmp/bazel-working-directory/_main/bazel-out/k8-fastbuild/bin/external/rules_rust~~crate~crate_index__bzip2-sys-0.1.11-1.0.8/bzip2-sys_bs.out_dir/lib/bzip2-1.0.8/decompress.o" "-c" "bzip2-1.0.8/decompress.c"
cargo:warning=In file included from bzip2-1.0.8/decompress.c:22:
cargo:warning=bzip2-1.0.8/bzlib_private.h:25:10: fatal error: 'stdlib.h' file not found
cargo:warning=#include <stdlib.h>
cargo:warning=         ^~~~~~~~~~
cargo:warning=1 error generated.
```

I think it is unfortunate and probably brings more weird errors up in
the future when the build command does not run in the same place where
every other bazel rule runs the compiler.

Bazel's `http_archive` and `http_file` use `~/.netrc` file to load HTTP
credentials.

Now rules_rust use the same approach if no other authorization
parameters are provided.

NOTE: `http_archive` supports passing a custom `netrc` and
`auth_patterns`. But this parameters are not added to the rust rules at
the moment.

---------

Co-authored-by: Daniel Wagner-Hall <[email protected]>

https://github.com/bazelbuild/buildtools/releases/tag/v7.1.1

Fixes #2626

https://blog.rust-lang.org/2024/05/02/Rust-1.78.0.html

)

closes #2324

The Cargo [Feature Resolver version
2](https://doc.rust-lang.org/cargo/reference/resolver.html#feature-resolver-version-2)
behavior is currently not supported by the `cargo metadata` sub command
(rust-lang/cargo#9863) which `crate_universe`
uses to determine the dependencies of a target, leading to inaccuracies
when dependencies are introduced via feature resolution for a particular
configuration.

In #1710 functionality was
added to use `cargo tree` to perform feature resolution for each
supported platform. This change expands on this trick to collect
dependency information at the same time and use that to determine
whether or not to include optional dependencies located in standard
`cargo metadata` output in the rendered Bazel targets. Non optional or
`target.cfg` (conditional) dependencies behave as they did before this
change.

Implementation details:
- `FeatureGenerator` was replaced by `TreeResolver`
- Optional dependencies are now rendered as selects on explicit
platforms. This will expand the size of `cargo-bazel-lock.json` files
but is expected to be more correct.

Fix is demonstrated by
https://github.com/UebelAndre/rules_rust/actions/runs/9018414504