run qmlcachegen on registered QML modules

Fixes KDAB#242

crates/cxx-qt-build/src/lib.rs

@@ -642,6 +642,9 @@ impl CxxQtBuilder {
             self.cc_builder.file(qml_module_registration_files.plugin);
             cc_builder_whole_archive.file(qml_module_registration_files.plugin_init);
             cc_builder_whole_archive.file(qml_module_registration_files.rcc);
+            for qmlcachegen_file in qml_module_registration_files.qmlcachegen {
+                cc_builder_whole_archive.file(qmlcachegen_file);
+            }
             self.cc_builder.define("QT_STATICPLUGIN", None);
             cc_builder_whole_archive_files_added = true;
         }

crates/qt-build-utils/src/lib.rs

@@ -122,6 +122,8 @@ pub struct QmlModuleRegistrationFiles {
     /// must be linked with [+whole-archive](https://doc.rust-lang.org/rustc/command-line-arguments.html#linking-modifiers-whole-archive)
     /// or the linker will discard the generated static variables because they are not referenced from `main`.
     pub rcc: PathBuf,
+    /// Files generated by [qmlcachegen](https://doc.qt.io/qt-6/qtqml-qtquick-compiler-tech.html). Must be linked with `+whole-archive`.
+    pub qmlcachegen: Vec<PathBuf>,
     /// File generated by [qmltyperegistrar](https://www.qt.io/blog/qml-type-registration-in-qt-5.15) CLI tool.
     pub qmltyperegistrar: PathBuf,
     /// File with generated [QQmlEngineExtensionPlugin](https://doc.qt.io/qt-6/qqmlengineextensionplugin.html) that calls the function generated by qmltyperegistrar.
@@ -672,6 +674,89 @@ prefer :/qt/qml/{qml_uri_dirs}/
             .expect("Could note write qrc file");
         }
 
+        // Run qmlcachegen
+        // qmlcachegen needs to be run once for each .qml file with --resource-path,
+        // then once for the module with --resource-name.
+        let mut qmlcachegen_file_paths = Vec::new();
+        if let Some(qmlcachegen_executable) = &self.qmlcachegen_executable {
+            let qmlcachegen_dir = format!("{out_dir}/qmlcachegen/{qml_uri_dirs}");
+            std::fs::create_dir_all(&qmlcachegen_dir)
+                .expect("Could not create qmlcachegen directory for QML module");
+
+            let common_args = vec![
+                "-i".to_string(),
+                qmldir_file_path.to_string(),
+                "--resource".to_string(),
+                qrc_path.clone(),
+            ];
+
+            let mut qml_file_qrc_paths = Vec::new();
+            for file in qml_files {
+                let qrc_resource_path =
+                    format!("/qt/qml/{qml_uri_dirs}/{}", file.as_ref().display());
+
+                let qml_compiled_file = format!(
+                    "{qmlcachegen_dir}/{}.cpp",
+                    file.as_ref().file_name().unwrap().to_string_lossy()
+                );
+                qmlcachegen_file_paths.push(PathBuf::from(&qml_compiled_file));
+
+                let specific_args = vec![
+                    "--resource-path".to_string(),
+                    qrc_resource_path.clone(),
+                    "-o".to_string(),
+                    qml_compiled_file,
+                    std::fs::canonicalize(file)
+                        .unwrap()
+                        .to_string_lossy()
+                        .to_string(),
+                ];
+
+                let cmd = Command::new(qmlcachegen_executable)
+                    .args(common_args.iter().chain(&specific_args))
+                    .output()
+                    .unwrap_or_else(|_| {
+                        panic!(
+                            "qmlcachegen failed for {} in QML module {uri}",
+                            file.as_ref().display()
+                        )
+                    });
+                if !cmd.status.success() {
+                    panic!(
+                        "qmlcachegen failed for {} in QML module {uri}:\n{}",
+                        file.as_ref().display(),
+                        String::from_utf8_lossy(&cmd.stderr)
+                    );
+                }
+                qml_file_qrc_paths.push(qrc_resource_path);
+            }
+
+            let qmlcachegen_loader = format!("{qmlcachegen_dir}/qmlcache_loader.cpp");
+            let specific_args = vec![
+                "--resource-name".to_string(),
+                format!("qmlcache_{qml_uri_underscores}"),
+                "-o".to_string(),
+                qmlcachegen_loader.clone(),
+            ];
+
+            let cmd = Command::new(qmlcachegen_executable)
+                .args(
+                    common_args
+                        .iter()
+                        .chain(&specific_args)
+                        .chain(&qml_file_qrc_paths),
+                )
+                .output()
+                .unwrap_or_else(|_| panic!("qmlcachegen failed for QML module {uri}"));
+            if !cmd.status.success() {
+                panic!(
+                    "qmlcachegen failed for QML module {uri}:\n{}",
+                    String::from_utf8_lossy(&cmd.stderr)
+                );
+            }
+            qmlcachegen_file_paths.push(PathBuf::from(&qmlcachegen_loader));
+        }
+
         // Run qmltyperegistrar
         let qmltyperegistrar_output_path = PathBuf::from(&format!(
             "{out_dir}/{qml_uri_underscores}_qmltyperegistration.cpp"
@@ -755,6 +840,7 @@ Q_IMPORT_PLUGIN({plugin_class_name});
 
         QmlModuleRegistrationFiles {
             rcc: self.qrc(&qrc_path),
+            qmlcachegen: qmlcachegen_file_paths,
             qmltyperegistrar: qmltyperegistrar_output_path,
             plugin: qml_plugin_cpp_path,
             plugin_init: qml_plugin_init_path,