Add env attribute to rust_binary (#1692)

This change allows users to set an `env` attribute on `rust_binary`
targets to then have environment variables defined for `bazel run`
invocations via the use of
[RunEnvironmentInfo](https://bazel.build/rules/lib/RunEnvironmentInfo).

docs/defs.md

@@ -92,7 +92,7 @@ Add additional rustc_flags from the command line with `--@rules_rust//:extra_rus
 
 <pre>
 rust_binary(<a href="#rust_binary-name">name</a>, <a href="#rust_binary-aliases">aliases</a>, <a href="#rust_binary-compile_data">compile_data</a>, <a href="#rust_binary-crate_features">crate_features</a>, <a href="#rust_binary-crate_name">crate_name</a>, <a href="#rust_binary-crate_root">crate_root</a>, <a href="#rust_binary-crate_type">crate_type</a>, <a href="#rust_binary-data">data</a>,
-            <a href="#rust_binary-deps">deps</a>, <a href="#rust_binary-edition">edition</a>, <a href="#rust_binary-experimental_use_cc_common_link">experimental_use_cc_common_link</a>, <a href="#rust_binary-linker_script">linker_script</a>, <a href="#rust_binary-malloc">malloc</a>, <a href="#rust_binary-out_binary">out_binary</a>,
+            <a href="#rust_binary-deps">deps</a>, <a href="#rust_binary-edition">edition</a>, <a href="#rust_binary-env">env</a>, <a href="#rust_binary-experimental_use_cc_common_link">experimental_use_cc_common_link</a>, <a href="#rust_binary-linker_script">linker_script</a>, <a href="#rust_binary-malloc">malloc</a>, <a href="#rust_binary-out_binary">out_binary</a>,
             <a href="#rust_binary-proc_macro_deps">proc_macro_deps</a>, <a href="#rust_binary-rustc_env">rustc_env</a>, <a href="#rust_binary-rustc_env_files">rustc_env_files</a>, <a href="#rust_binary-rustc_flags">rustc_flags</a>, <a href="#rust_binary-srcs">srcs</a>, <a href="#rust_binary-stamp">stamp</a>, <a href="#rust_binary-version">version</a>)
 </pre>
 
@@ -198,6 +198,7 @@ is available under the key `dsym_folder` in `OutputGroupInfo`.
 | <a id="rust_binary-data"></a>data |  List of files used by this rule at compile time and runtime.<br><br>If including data at compile time with include_str!() and similar, prefer <code>compile_data</code> over <code>data</code>, to prevent the data also being included in the runfiles.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | optional | <code>[]</code> |
 | <a id="rust_binary-deps"></a>deps |  List of other libraries to be linked to this library target.<br><br>These can be either other <code>rust_library</code> targets or <code>cc_library</code> targets if linking a native library.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | optional | <code>[]</code> |
 | <a id="rust_binary-edition"></a>edition |  The rust edition to use for this crate. Defaults to the edition specified in the rust_toolchain.   | String | optional | <code>""</code> |
+| <a id="rust_binary-env"></a>env |  Specifies additional environment variables to set when the target is executed by bazel run. Values are subject to <code>$(rootpath)</code>, <code>$(execpath)</code>, location, and ["Make variable"](https://docs.bazel.build/versions/master/be/make-variables.html) substitution.<br><br>Execpath returns absolute path, and in order to be able to construct the absolute path we need to wrap the test binary in a launcher. Using a launcher comes with complications, such as more complicated debugger attachment.   | <a href="https://bazel.build/rules/lib/dict">Dictionary: String -> String</a> | optional | <code>{}</code> |
 | <a id="rust_binary-experimental_use_cc_common_link"></a>experimental_use_cc_common_link |  Whether to use cc_common.link to link rust binaries. Possible values: [-1, 0, 1]. -1 means use the value of the toolchain.experimental_use_cc_common_link boolean build setting to determine. 0 means do not use cc_common.link (use rustc instead). 1 means use cc_common.link.   | Integer | optional | <code>-1</code> |
 | <a id="rust_binary-linker_script"></a>linker_script |  Link script to forward into linker via rustc options.   | <a href="https://bazel.build/concepts/labels">Label</a> | optional | <code>None</code> |
 | <a id="rust_binary-malloc"></a>malloc |  Override the default dependency on <code>malloc</code>.<br><br>By default, Rust binaries linked with cc_common.link are linked against <code>@bazel_tools//tools/cpp:malloc"</code>, which is an empty library and the resulting binary will use libc's <code>malloc</code>. This label must refer to a <code>cc_library</code> rule.   | <a href="https://bazel.build/concepts/labels">Label</a> | optional | <code>@bazel_tools//tools/cpp:malloc</code> |

docs/flatten.md

@@ -233,7 +233,7 @@ A toolchain for [rust-analyzer](https://rust-analyzer.github.io/).
 
 <pre>
 rust_binary(<a href="#rust_binary-name">name</a>, <a href="#rust_binary-aliases">aliases</a>, <a href="#rust_binary-compile_data">compile_data</a>, <a href="#rust_binary-crate_features">crate_features</a>, <a href="#rust_binary-crate_name">crate_name</a>, <a href="#rust_binary-crate_root">crate_root</a>, <a href="#rust_binary-crate_type">crate_type</a>, <a href="#rust_binary-data">data</a>,
-            <a href="#rust_binary-deps">deps</a>, <a href="#rust_binary-edition">edition</a>, <a href="#rust_binary-experimental_use_cc_common_link">experimental_use_cc_common_link</a>, <a href="#rust_binary-linker_script">linker_script</a>, <a href="#rust_binary-malloc">malloc</a>, <a href="#rust_binary-out_binary">out_binary</a>,
+            <a href="#rust_binary-deps">deps</a>, <a href="#rust_binary-edition">edition</a>, <a href="#rust_binary-env">env</a>, <a href="#rust_binary-experimental_use_cc_common_link">experimental_use_cc_common_link</a>, <a href="#rust_binary-linker_script">linker_script</a>, <a href="#rust_binary-malloc">malloc</a>, <a href="#rust_binary-out_binary">out_binary</a>,
             <a href="#rust_binary-proc_macro_deps">proc_macro_deps</a>, <a href="#rust_binary-rustc_env">rustc_env</a>, <a href="#rust_binary-rustc_env_files">rustc_env_files</a>, <a href="#rust_binary-rustc_flags">rustc_flags</a>, <a href="#rust_binary-srcs">srcs</a>, <a href="#rust_binary-stamp">stamp</a>, <a href="#rust_binary-version">version</a>)
 </pre>
 
@@ -339,6 +339,7 @@ is available under the key `dsym_folder` in `OutputGroupInfo`.
 | <a id="rust_binary-data"></a>data |  List of files used by this rule at compile time and runtime.<br><br>If including data at compile time with include_str!() and similar, prefer <code>compile_data</code> over <code>data</code>, to prevent the data also being included in the runfiles.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | optional | <code>[]</code> |
 | <a id="rust_binary-deps"></a>deps |  List of other libraries to be linked to this library target.<br><br>These can be either other <code>rust_library</code> targets or <code>cc_library</code> targets if linking a native library.   | <a href="https://bazel.build/concepts/labels">List of labels</a> | optional | <code>[]</code> |
 | <a id="rust_binary-edition"></a>edition |  The rust edition to use for this crate. Defaults to the edition specified in the rust_toolchain.   | String | optional | <code>""</code> |
+| <a id="rust_binary-env"></a>env |  Specifies additional environment variables to set when the target is executed by bazel run. Values are subject to <code>$(rootpath)</code>, <code>$(execpath)</code>, location, and ["Make variable"](https://docs.bazel.build/versions/master/be/make-variables.html) substitution.<br><br>Execpath returns absolute path, and in order to be able to construct the absolute path we need to wrap the test binary in a launcher. Using a launcher comes with complications, such as more complicated debugger attachment.   | <a href="https://bazel.build/rules/lib/dict">Dictionary: String -> String</a> | optional | <code>{}</code> |
 | <a id="rust_binary-experimental_use_cc_common_link"></a>experimental_use_cc_common_link |  Whether to use cc_common.link to link rust binaries. Possible values: [-1, 0, 1]. -1 means use the value of the toolchain.experimental_use_cc_common_link boolean build setting to determine. 0 means do not use cc_common.link (use rustc instead). 1 means use cc_common.link.   | Integer | optional | <code>-1</code> |
 | <a id="rust_binary-linker_script"></a>linker_script |  Link script to forward into linker via rustc options.   | <a href="https://bazel.build/concepts/labels">Label</a> | optional | <code>None</code> |
 | <a id="rust_binary-malloc"></a>malloc |  Override the default dependency on <code>malloc</code>.<br><br>By default, Rust binaries linked with cc_common.link are linked against <code>@bazel_tools//tools/cpp:malloc"</code>, which is an empty library and the resulting binary will use libc's <code>malloc</code>. This label must refer to a <code>cc_library</code> rule.   | <a href="https://bazel.build/concepts/labels">Label</a> | optional | <code>@bazel_tools//tools/cpp:malloc</code> |

rust/private/rust.bzl

@@ -231,7 +231,7 @@ def _rust_binary_impl(ctx):
         crate_root = crate_root_src(ctx.attr.name, ctx.files.srcs, ctx.attr.crate_type)
     srcs, crate_root = transform_sources(ctx, ctx.files.srcs, crate_root)
 
-    return rustc_compile_action(
+    providers = rustc_compile_action(
         ctx = ctx,
         attr = ctx.attr,
         toolchain = toolchain,
@@ -255,6 +255,16 @@ def _rust_binary_impl(ctx):
         ),
     )
 
+    providers.append(RunEnvironmentInfo(
+        environment = expand_dict_value_locations(
+            ctx,
+            ctx.attr.env,
+            ctx.attr.data,
+        ),
+    ))
+
+    return providers
+
 def _rust_test_impl(ctx):
     """The implementation of the `rust_test` rule.
 
@@ -940,6 +950,18 @@ _rust_binary_attrs = dict({
         """),
         default = "bin",
     ),
+    "env": attr.string_dict(
+        mandatory = False,
+        doc = dedent("""\
+            Specifies additional environment variables to set when the target is executed by bazel run.
+            Values are subject to `$(rootpath)`, `$(execpath)`, location, and
+            ["Make variable"](https://docs.bazel.build/versions/master/be/make-variables.html) substitution.
+
+            Execpath returns absolute path, and in order to be able to construct the absolute path we
+            need to wrap the test binary in a launcher. Using a launcher comes with complications, such as
+            more complicated debugger attachment.
+        """),
+    ),
     "linker_script": attr.label(
         doc = dedent("""\
             Link script to forward into linker via rustc options.