Add check to prevent forgetting GTK initialization checks

Author: GuillaumeGomez

gtk/tests/check_subclass_panic.rs

@@ -0,0 +1,69 @@
+// Take a look at the license at the top of the repository in the LICENSE file.
+
+// We want to ensure that all subclasses have:
+//
+// ```
+// if !crate::rt::is_initialized() {
+//     panic!("GTK has to be initialized first");
+// }
+// ```
+
+use std::fs::{read_dir, read_to_string};
+use std::path::Path;
+
+fn check_file(f: &Path) -> usize {
+    let s = read_to_string(f).expect("cannot read file");
+    let mut checking_type: Option<String> = None;
+    let mut found_is_initialized_check = false;
+
+    for line in s.lines() {
+        if checking_type.is_none() {
+            if !line.starts_with("unsafe impl") || !line.contains(" IsSubclassable<") {
+                continue;
+            }
+            if let Some(for_) = line.split(" for ").nth(1).and_then(|s| s.split(' ').next()) {
+                checking_type = Some(for_.to_owned());
+            }
+            continue;
+        }
+        if line == "}" {
+            // Analysis complete!
+            break;
+        }
+        let trimmed = line.trim();
+        if trimmed.contains("is_initialized()") {
+            found_is_initialized_check = true;
+        }
+    }
+    if !found_is_initialized_check {
+        if let Some(for_) = checking_type {
+            if for_ == "Application" {
+                return 0;
+            }
+            eprintln!(
+                "[{}] Missing `is_initialized()` check in subclass implementation (`{}`)",
+                f.display(),
+                for_
+            );
+            1
+        } else {
+            0
+        }
+    } else {
+        0
+    }
+}
+
+#[test]
+fn check_subclass_panic() {
+    let mut errors = 0;
+
+    for entry in read_dir("src/subclass").unwrap() {
+        let entry = entry.expect("invalid entry");
+        let path = entry.path();
+        if path.is_file() {
+            errors += check_file(&path);
+        }
+    }
+    assert!(errors == 0);
+}