draft: fix data and compile_data for rust_doc

[paulfariello]

Try to fix #1572

Main issue is that data_paths do not inherit from original crate when building rust_doc (and probably rust_test).
The main idea is to rely on crate_info which inherit correctly from original crate.

Issue with this draft is that compile_data is filed with File instead of Target when building 3rd party crate.

ERROR: <redacted>__base64-0.13.1/BUILD.bazel:34:13: in rust_library rule @<redacted>__base64-0.13.1//:base64:
Traceback (most recent call last):
	File "external/rules_rust/rust/private/rust.bzl", line 197, column 32, in _rust_library_impl
		return _rust_library_common(ctx, "rlib")
	File "external/rules_rust/rust/private/rust.bzl", line 292, column 32, in _rust_library_common
		return rustc_compile_action(
	File "external/rules_rust/rust/private/rustc.bzl", line 1093, column 46, in rustc_compile_action
		args, env_from_args = construct_arguments(
	File "external/rules_rust/rust/private/rustc.bzl", line 915, column 38, in construct_arguments
		expand_list_element_locations(
	File "external/rules_rust/rust/private/utils.bzl", line 311, column 53, in expand_list_element_locations
		return [_expand_location_for_build_script_runner(ctx, arg, data) for arg in args]
	File "external/rules_rust/rust/private/utils.bzl", line 255, column 30, in _expand_location_for_build_script_runner
		dedup_expand_location(ctx, env, data),
	File "external/rules_rust/rust/private/utils.bzl", line 230, column 31, in dedup_expand_location
		return ctx.expand_location(input, _deduplicate(targets))
Error in expand_location: at index 0 of targets, got element of type File, want Target

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[illicitonion]

Thanks for putting together this fix!

It looks like the issue is that whenever we construct a CrateInfo (which we do several times in rust/private/rust.bzl, for instance), we convert compile_data from an attribute (targets) to files as required by the CrateInfo provider (by using ctx.files.compile_data instead of ctx.attr.compile_data).

I think to fix this we'd need to:

1. Modify CrateInfo to have an additional field, compile_data_targets here:

   rules_rust/rust/private/providers.bzl

   Lines 17 to 43 in d5289ad

   	CrateInfo = provider(
   	doc = "A provider containing general Crate information.",
   	fields = {
   	"aliases": "Dict[Label, String]: Renamed and aliased crates",
   	"compile_data": "depset[File]: Compile data required by this crate.",
   	"deps": "depset[DepVariantInfo]: This crate's (rust or cc) dependencies' providers.",
   	"edition": "str: The edition of this crate.",
   	"is_test": "bool: If the crate is being compiled in a test context",
   	"metadata": "File: The rmeta file produced for this crate. It is optional.",
   	"name": "str: The name of this crate.",
   	"output": "File: The output File that will be produced, depends on crate type.",
   	"owner": "Label: The label of the target that produced this CrateInfo",
   	"proc_macro_deps": "depset[DepVariantInfo]: This crate's rust proc_macro dependencies' providers.",
   	"root": "File: The source File entrypoint to this crate, eg. lib.rs",
   	"rustc_env": "Dict[String, String]: Additional `\"key\": \"value\"` environment variables to set for rustc.",
   	"rustc_env_files": "[File]: Files containing additional environment variables to set for rustc.",
   	"srcs": "depset[File]: All source Files that are part of the crate.",
   	"type": (
   	"str: The type of this crate " +
   	"(see [rustc --crate-type](https://doc.rust-lang.org/rustc/command-line-arguments.html#--crate-type-a-list-of-types-of-crates-for-the-compiler-to-emit))."
   	),
   	"wrapped_crate_type": (
   	"str, optional: The original crate type for targets generated using a previously defined " +
   	"crate (typically tests using the `rust_test::crate` attribute)"
   	),
   	},
   	)

2. Wherever we construct a CrateInfo, start also setting this field (to ctx.attr.compile_data rather than ctx.files.compile_data)
3. In your change, consume compile_data_targets rather than compile_data.

Then I suspect your change will start working 🤞

[illicitonion]

LGTM! Last up, can you add a test which was failing without this change, which shows rust_doc now works with compile_data?

Thanks!

[paulfariello]

For the record, the added test would fail on main branch at build time with the following error:

INFO: Invocation ID: 6aec52b5-1be1-471a-8513-af33247b3398
ERROR: /home/redacted/rules_rust/test/unit/compile_data/BUILD.bazel:3:24: in rust_doc rule //test/unit/compile_data:compile_data_env_rust_doc: label '//test/unit/compile_data:compile_data.txt' in $(location) expression is not a declared prerequisite of this rule
ERROR: /home/redacted/rules_rust/test/unit/compile_data/BUILD.bazel:3:24: in (an implicit dependency) attribute of rust_doc rule //test/unit/compile_data:compile_data_env_rust_doc: $(location) not defined. Since this rule was created by the macro 'compile_data_test_suite', the error might have been caused by the macro implementation
ERROR: /home/redacted/rules_rust/test/unit/compile_data/BUILD.bazel:3:24: Analysis of target '//test/unit/compile_data:compile_data_env_rust_doc' failed
ERROR: Analysis of target '//test/unit/compile_data:compile_data_env_rust_doc' failed; build aborted:
INFO: Elapsed time: 8.315s
INFO: 0 processes.
FAILED: Build did NOT complete successfully (107 packages loaded, 1951 targets configured)
ERROR: Couldn't start the build. Unable to run tests

[illicitonion]

LGTM - thanks for putting this all together! Two tiny suggestions and we're good to go!