cli-flags: Don't ignore the first flag in `CommonOptions::parse_from_str` (#4642)

crates/cli-flags/src/lib.rs

@@ -229,7 +229,11 @@ pub struct CommonOptions {
 
 impl CommonOptions {
     pub fn parse_from_str(s: &str) -> Result<Self> {
-        let parts = s.split(" ");
+        let parts = s.split(" ").filter(|s| !s.is_empty());
+        // The first argument is the name of the executable, which we don't use
+        // here, but have to provide because `clap` skips over it, and otherwise
+        // our first CLI flag will be ignored.
+        let parts = Some("wasmtime").into_iter().chain(parts);
         let options =
             Self::try_parse_from(parts).context("unable to parse options from passed flags")?;
         Ok(options)
@@ -722,11 +726,11 @@ mod test {
 
         assert_eq!(use_func(""), use_clap_parser(&[]));
         assert_eq!(
-            use_func("foo --wasm-features=threads"),
+            use_func("--wasm-features=threads"),
             use_clap_parser(&["foo", "--wasm-features=threads"])
         );
         assert_eq!(
-            use_func("foo --cranelift-set enable_simd=true"),
+            use_func("--cranelift-set enable_simd=true"),
             use_clap_parser(&["foo", "--cranelift-set", "enable_simd=true"])
         );
     }