add rustdoc feature support

Author: TroyKomodo

rust/private/providers.bzl

@@ -36,6 +36,7 @@ CrateInfo = provider(
         "rustc_rmeta_output": "File: The rmeta file produced for this crate. It is optional.",
         "srcs": "depset[File]: All source Files that are part of the crate.",
         "std_dylib": "File: libstd.so file",
+        "crate_features": "[str]: A list of feature enabled for this 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))."

rust/private/rust.bzl

@@ -206,6 +206,7 @@ def _rust_library_common(ctx, crate_type):
             compile_data = depset(compile_data),
             compile_data_targets = depset(ctx.attr.compile_data),
             owner = ctx.label,
+            crate_features = ctx.attr.crate_features,
         ),
     )
 

rust/private/rustdoc.bzl

@@ -207,6 +207,9 @@ def _rust_doc_impl(ctx):
     ]
     rustdoc_flags.extend(ctx.attr.rustdoc_flags)
 
+    if ctx.attr.include_features:
+        rustdoc_flags.extend(["--cfg=feature=\"{}\"".format(feature) for feature in crate_info.crate_features])
+
     action = rustdoc_compile_action(
         ctx = ctx,
         toolchain = find_toolchain(ctx),
@@ -321,6 +324,10 @@ rust_doc = rule(
                 file of arguments to rustc: `@$(location //package:target)`.
             """),
         ),
+        "include_features": attr.bool(
+            doc = "Include the features defined by `crate_features` when building the doc tests."
+            default = True
+        ),
         "_dir_zipper": attr.label(
             doc = "A tool that orchestrates the creation of zip archives for rustdoc outputs.",
             default = Label("//rust/private/rustdoc/dir_zipper"),

rust/private/rustdoc_test.bzl

@@ -129,6 +129,7 @@ def _rust_doc_test_impl(ctx):
         compile_data = crate.compile_data,
         compile_data_targets = crate.compile_data_targets,
         wrapped_crate_type = crate.type,
+        crate_features = crate.crate_features,
         owner = ctx.label,
     )
 
@@ -150,6 +151,9 @@ def _rust_doc_test_impl(ctx):
         "--test",
     ]
 
+    if ctx.attr.include_features:
+        rustdoc_flags.extend(["--cfg=feature=\"{}\"".format(feature) for feature in crate_info.crate_features])
+
     action = rustdoc_compile_action(
         ctx = ctx,
         toolchain = toolchain,
@@ -228,6 +232,10 @@ rust_doc_test = rule(
             default = Label("//rust/private/rustdoc:rustdoc_test_writer"),
             executable = True,
         ),
+        "include_features": attr.bool(
+            doc = "Include the features defined by `crate_features` when building the doc tests."
+            default = True
+        )
     },
     test = True,
     fragments = ["cpp"],