build: make it possible to pass arbitrary env vars to rustc

build_extra/rust/run.py

 #!/usr/bin/env python
 # Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
-# This file just executes its arguments, except that also adds GN_OUT_DIR and
-# CARGO_PKG_VERSION to the environ. This is for compatibility with cargo.
+
+# This file just executes its arguments, except that it allows overriding
+# environment variables using command-line arguments.
+
 import subprocess
 import sys
 import os
 import re
 
-args = sys.argv[1:]
+args = []
 env = os.environ.copy()
 
 if sys.platform == 'win32':
@@ -27,24 +29,19 @@ if sys.platform == 'win32':
 env["GN_OUT_DIR"] = os.path.abspath(".")
 assert os.path.isdir(env["GN_OUT_DIR"])
 
-# Some crates (e.g. 'typenum') generate source files and place them in the
-# directory indicated by the 'OUT_DIR' environment variable, which is normally
-# set by Cargo. We pre-generate these files and store them in the source repo.
-# Therefore, set 'OUT_DIR' so these crates can find their generated sources.
-for i, arg in enumerate(args):
-    match = re.search('--generated-source-dir=(.*)', arg)
-    if match:
-        env["OUT_DIR"] = os.path.abspath(match.group(1))
-        del args[i]
-        break
-
-# Set the CARGO_PKG_VERSION env variable if provided as an argument
-# When building with Cargo this variable is set automatically
-for i, arg in enumerate(args):
-    match = re.search('--cargo-pkg-version="?([^"]*)"?', arg)
+# Environment variables can be specified on the command line using
+# '--env=variable=value' flags. These flags are not passed through to rustc.
+# This is useful to set env vars that are normally automatically set by Cargo,
+# e.g. CARGO_PKG_NAME, CARGO_PKG_VERSION, OUT_DIR, etc.
+for arg in sys.argv[1:]:
+    match = re.search('--env=([^=]+)=(.*)', arg)
     if match:
-        env["CARGO_PKG_VERSION"] = match.group(1)
-        del args[i]
-        break
+        key, value = match.groups()
+        if key == "OUT_DIR":
+            # OUT_DIR needs to contain an absolute path.
+            value = os.path.abspath(value)
+        env[key] = value
+    else:
+        args.append(arg)
 
 sys.exit(subprocess.call(args, env=env))

build_extra/rust/rust.gni

@@ -63,6 +63,7 @@ template("_rust_crate") {
                            "crate_version",
                            "deps",
                            "edition",
+                           "env",
                            "features",
                            "generated_source_dir",
                            "inputs",
@@ -234,24 +235,6 @@ template("_rust_crate") {
       "--color=always",
     ]
 
-    if (defined(generated_source_dir)) {
-      args += [
-        # Some crates (e.g. 'typenum') generate source files and place them in
-        # the directory indicated by the 'OUT_DIR' environment variable, which
-        # is normally set by Cargo. This flag tells run.py to set 'OUT_DIR' to
-        # the path where the current crate can find its generated sources.
-        "--generated-source-dir=" +
-            rebase_path(generated_source_dir, root_build_dir),
-      ]
-    }
-
-    if (defined(crate_version)) {
-      args += [
-        # This is used to set env variables for Cargo build compatibility
-        "--cargo-pkg-version=$crate_version",
-      ]
-    }
-
     if (is_win) {
       # Proc-macro crates need to be linked by rustc itself, because rustc
       # doesn't expose all the information necessary to produce the correct
@@ -318,6 +301,22 @@ template("_rust_crate") {
       sources += [ info.out_path ]
       deps += [ info.label ]
     }
+
+    if (defined(generated_source_dir)) {
+      args += [
+        # Some crates (e.g. 'typenum') generate source files and place them in
+        # the directory indicated by the 'OUT_DIR' environment variable, which
+        # is normally set by Cargo. This flag tells run.py to set 'OUT_DIR' to
+        # the path where the current crate can find its generated sources.
+        "--env=OUT_DIR=" + rebase_path(generated_source_dir, root_build_dir),
+      ]
+    }
+
+    if (defined(env)) {
+      foreach(e, env) {
+        args += [ "--env=$e" ]
+      }
+    }
   }
 }
 

cli/BUILD.gn

@@ -179,10 +179,10 @@ rust_executable("deno") {
   # Extract version from Cargo.toml
   # TODO integrate this into rust.gni by allowing the rust_executable template
   # to specify a cargo.toml from which it will extract a version.
-  crate_version = deno_cargo_info.version
   inputs = [
     "Cargo.toml",
   ]
+  env = [ "CARGO_PKG_VERSION=${deno_cargo_info.version}" ]
 }
 
 rust_test("cli_test") {
@@ -194,10 +194,10 @@ rust_test("cli_test") {
   ]
 
   # Extract version from Cargo.toml
-  crate_version = deno_cargo_info.version
   inputs = [
     "Cargo.toml",
   ]
+  env = [ "CARGO_PKG_VERSION=${deno_cargo_info.version}" ]
 }
 
 # Generates the core TypeScript type library for deno that will be