Add an env_flags attribute to rust_library/binary rules

* Accept passing environment variables through "--env=NAME=VAL" flags
* Add two rust internal tools to assist environment variable flags processing

Signed-off-by: Yuxuan Dai <[email protected]>

Author: yxdai-nju

prelude/decls/rust_common.bzl

@@ -112,6 +112,15 @@ def _env_arg():
 """),
     }
 
+def _env_flags_arg():
+    return {
+        "env_flags": attrs.list(attrs.arg(), default = [], doc = """
+    A sequence of "--env=NAME=VAL" flags for additional environment variables for this rule's
+     invocations of rustc. For example `env_flags = ["--env=NAME1=val1", "--env=NAME2=val2"]`.
+     The environment variable values may include macros which are expanded.
+"""),
+    }
+
 def _run_env_arg():
     return {
         "run_env": attrs.dict(key = attrs.string(), value = attrs.arg(), sorted = False, default = {}, doc = """
@@ -186,6 +195,7 @@ rust_common = struct(
     crate_root = _crate_root,
     default_roots_arg = _default_roots_arg,
     env_arg = _env_arg,
+    env_flags_arg = _env_flags_arg,
     run_env_arg = _run_env_arg,
     build_and_run_env_arg = _build_and_run_env_arg,
     mapped_srcs_arg = _mapped_srcs_arg,

prelude/decls/rust_rules.bzl

@@ -121,6 +121,7 @@ rust_binary = prelude_rule(
         rust_common.crate(crate_type = attrs.option(attrs.string(), default = None)) |
         rust_common.crate_root() |
         rust_common.env_arg() |
+        rust_common.env_flags_arg() |
         _rust_binary_attrs_group(prefix = "") |
         _rust_common_attributes(is_binary = True) |
         _RUST_EXECUTABLE_ATTRIBUTES |
@@ -186,6 +187,7 @@ rust_library = prelude_rule(
         rust_common.linker_flags_arg() |
         rust_common.exported_linker_flags_arg() |
         rust_common.env_arg() |
+        rust_common.env_flags_arg() |
         rust_common.crate(crate_type = attrs.option(attrs.string(), default = None)) |
         rust_common.crate_root() |
         native_common.preferred_linkage(preferred_linkage_type = attrs.enum(Linkage.values(), default = "any")) |

prelude/rust/build.bzl

@@ -1540,6 +1540,8 @@ def _rustc_invoke(
         compile_cmd.add(cmd_args("--env=", k, "=", v, delimiter = ""))
     for k, v in path_env.items():
         compile_cmd.add(cmd_args("--path-env=", k, "=", v, delimiter = ""))
+    for flag in ctx.attrs.env_flags:
+        compile_cmd.add(cmd_args(flag))
 
     build_status = None
     if infallible_diagnostics: