forward build-time env vars to binary, and test that we do

cargo-miri/bin.rs

@@ -372,6 +372,16 @@ path = "lib.rs"
 }
 
 fn phase_cargo_miri(mut args: env::Args) {
+    // Check for version and help flags even when invoked as `cargo-miri`.
+    if has_arg_flag("--help") || has_arg_flag("-h") {
+        show_help();
+        return;
+    }
+    if has_arg_flag("--version") || has_arg_flag("-V") {
+        show_version();
+        return;
+    }
+
     // Require a subcommand before any flags.
     // We cannot know which of those flags take arguments and which do not,
     // so we cannot detect subcommands later.
@@ -567,6 +577,13 @@ fn phase_cargo_runner(binary: &str, binary_args: env::Args) {
     let info: CrateRunInfo = serde_json::from_reader(file)
         .unwrap_or_else(|_| show_error(format!("File {:?} does not contain valid JSON", binary)));
 
+    // Set missing env vars.
+    for (name, val) in info.env {
+        if env::var_os(&name).is_none() {
+            env::set_var(name, val);
+        }
+    }
+
     let mut cmd = miri();
     // Forward rustc arguments. We need to patch "--extern" filenames because
     // we forced a check-only build without cargo knowing about that: replace `.rlib` suffix by `.rmeta`.
@@ -610,16 +627,6 @@ fn phase_cargo_runner(binary: &str, binary_args: env::Args) {
 }
 
 fn main() {
-    // Check for version and help flags even when invoked as `cargo-miri`.
-    if has_arg_flag("--help") || has_arg_flag("-h") {
-        show_help();
-        return;
-    }
-    if has_arg_flag("--version") || has_arg_flag("-V") {
-        show_version();
-        return;
-    }
-
     // Rustc does not support non-UTF-8 arguments so we make no attempt either.
     // (We do support non-UTF-8 environment variables though.)
     let mut args = std::env::args();

test-cargo-miri/test.stdout.ref

@@ -4,7 +4,7 @@ running 1 test
 test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
 
 
-running 7 tests
-.i.....
-test result: ok. 6 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out
+running 8 tests
+..i.....
+test result: ok. 7 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out
 

test-cargo-miri/test.stdout.ref2

@@ -7,5 +7,5 @@ test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 1 filtered out
 running 1 test
 test simple1 ... ok
 
-test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 6 filtered out
+test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 7 filtered out
 

test-cargo-miri/test.stdout.ref3

@@ -7,5 +7,5 @@ test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 1 filtered out
 running 1 test
 test num_cpus ... ok
 
-test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 6 filtered out
+test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 7 filtered out
 

test-cargo-miri/test.stdout.ref4

@@ -1,5 +1,6 @@
 
-running 7 tests
+running 8 tests
+test cargo_env ... ok
 test do_panic ... ok
 test does_not_work_on_miri ... ignored
 test entropy_rng ... ok
@@ -8,5 +9,5 @@ test num_cpus ... ok
 test simple1 ... ok
 test simple2 ... ok
 
-test result: ok. 6 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out
+test result: ok. 7 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out
 

test-cargo-miri/tests/test.rs

@@ -42,6 +42,11 @@ fn num_cpus() {
     assert_eq!(num_cpus::get(), 1);
 }
 
+#[test]
+fn cargo_env() {
+    assert_eq!(env!("CARGO_PKG_NAME"), "cargo-miri-test");
+    env!("CARGO_BIN_EXE_cargo-miri-test"); // Asserts that this exists.
+}
 
 // FIXME: Remove this `cfg` once we fix https://github.com/rust-lang/miri/issues/1059.
 // We cfg-gate the `should_panic` attribute and the `panic!` itself, so that the test