gtk4-macros: Wait for blueprint-compiler process in all branches

Otherwise clippy complains and zombie processes might stay around.

Also make sure to never panic on normal errors for the same reason, and
provide more useful error messages.

gtk4-macros/src/blueprint.rs

@@ -1,29 +1,33 @@
 // Take a look at the license at the top of the repository in the LICENSE file.
 
 use std::{
-    io::{Error, ErrorKind, Result, Write},
+    io::Write,
     process::{Command, Stdio},
 };
 
-pub(crate) fn compile_blueprint(blueprint: &[u8]) -> Result<String> {
+pub(crate) fn compile_blueprint(blueprint: &[u8]) -> Result<String, String> {
     let mut compiler = Command::new("blueprint-compiler")
         .args(["compile", "-"])
         .stdin(Stdio::piped())
         .stdout(Stdio::piped())
         .spawn()
-        .unwrap_or_else(|_| panic!("blueprint-compiler not found"));
+        .map_err(|e| format!("blueprint-compiler couldn't be spawned: {e}"))?;
     let mut stdin = compiler.stdin.take().unwrap();
-    stdin.write_all(blueprint)?;
+    if let Err(e) = stdin.write_all(blueprint) {
+        let _ = compiler.wait();
+        return Err(format!(
+            "Couldn't send blueprint to blueprint-compiler: {e}"
+        ));
+    }
     drop(stdin);
 
     let output = compiler
         .wait_with_output()
-        .unwrap_or_else(|e| panic!("blueprint-compiler process failed {e}"));
+        .map_err(|e| format!("blueprint-compiler process failed: {e}"))?;
 
     let buf = String::from_utf8(output.stdout).unwrap();
-
     if !buf.starts_with('<') {
-        return Err(Error::new(ErrorKind::Other, buf));
+        return Err(format!("blueprint-compiler failed: {buf}"));
     }
 
     Ok(buf)