FEAT: Add --config option for miri flags

cargo-miri/src/phases.rs

@@ -181,6 +181,7 @@ pub fn phase_cargo_miri(mut args: impl Iterator<Item = String>) {
     let target_dir = get_target_dir(&metadata);
     cmd.arg("--target-dir").arg(target_dir);
 
+    cmd.args(get_miriflags());
     // Store many-seeds argument.
     let mut many_seeds = None;
     // *After* we set all the flags that need setting, forward everything else. Make sure to skip

cargo-miri/src/util.rs

@@ -88,6 +88,12 @@ pub fn escape_for_toml(s: &str) -> String {
     format!("\"{s}\"")
 }
 
+pub fn flagsplit(flags: &str) -> Vec<String> {
+    // This code is taken from `RUSTFLAGS` handling in cargo.
+    // Taken from miri-script util.rs
+    flags.split(' ').map(str::trim).filter(|s| !s.is_empty()).map(str::to_string).collect()
+}
+
 pub fn get_miriflags() -> Vec<String> {
     // TODO: I quite not understand what Carl Jung means by Oh and please add a link to https://doc.rust-lang.org/cargo/reference/config.html#buildrustflags.
     // I guess we don't support the target.rustflags part yet? (That's okay but should be mentioned in a comment.)
@@ -102,10 +108,33 @@ pub fn get_miriflags() -> Vec<String> {
     // Respect `MIRIFLAGS` and `miri.flags` setting in cargo config.
     // If MIRIFLAGS is present, flags from cargo config are ignored.
     // This matches cargo behavior for RUSTFLAGS.
-    if let Ok(a) = env::var("MIRIFLAGS") {
+    //
+    // Strategy: (1) check pseudo var CARGO_ENCODED_MIRIFLAGS first (this is only set after we check for --config
+    // in the cargo_dash_dash in the if else)
+    //
+    // if CARGO_ENCODED_MIRIFLAGS doesn't exist, we check in --config (2)
+    // if --config doesn't exist, we check offical env var MIRIFLAGS (3)
+    //
+    // if MIRIFLAGS is non-existent, we then check for toml (4)
+    let cargo_dash_dash_config = cargo_extra_flags();
+    if let Ok(cargo_encoded_miri_flags) = env::var("CARGO_ENCODED_MIRIFLAGS") {
+        // (1)
+        flagsplit(cargo_encoded_miri_flags.as_str())
+    } else if cargo_dash_dash_config.contains(&"miri".to_string()) {
+        // (2)
+        let miri_flags_vec = cargo_dash_dash_config
+            .into_iter()
+            .filter(|arg| arg.contains(&"miri".to_string()))
+            .collect::<Vec<String>>();
+        let miri_flags_string = miri_flags_vec.join(" ");
+        env::set_var("CARGO_ENCODED_MIRIFLAGS", miri_flags_string);
+        miri_flags_vec
+    } else if let Ok(a) = env::var("MIRIFLAGS") {
+        // (3)
         // This code is taken from `RUSTFLAGS` handling in cargo.
         a.split(' ').map(str::trim).filter(|s| !s.is_empty()).map(str::to_string).collect()
     } else {
+        // (4)
         serde_json::from_str::<Vec<String>>(config_miriflags).unwrap_or_default()
     }
 }