Be able to call JNI method from thread

README.md

@@ -31,6 +31,14 @@ but you can switch to `#[call_type(unchecked)]` at any time, most likely with fe
 
 You can also force a Java type on input arguments via `#[input_type]` attribute, which can be useful for Android JNI development for example.
 
+### Android specificities
+
+On Android App, to call a Java class from rust the JVM use the callstack to find desired class.
+But when in a rust thread, you don't have a call stack anymore.\
+So to be able to call a Java class you have to pass the class reference rather than the string class path.
+
+You can find an example of this usage in `robusta-android-example/src/thread_func.rs`
+
 ## Code example
 
 You can find an example under `./robusta-example`. To run it you should have `java` and `javac` on your PATH and then execute:

robusta-android-example/robustaAndroidExample/app/src/main/java/com/example/robustaandroidexample/RobustaAndroidExample.java

@@ -14,5 +14,13 @@ public static String getAppFilesDir(Context context) {
         Log.d("ROBUSTA_ANDROID_EXAMPLE", "getAppFilesDir IN");
         return context.getFilesDir().toString();
     }
+    public static int threadTestNoClass(String s) {
+        Log.d("ROBUSTA_ANDROID_EXAMPLE", "threadTestNoClass IN: " + s);
+        return 10;
+    }
+    public static int threadTestWithClass(String s) {
+        Log.d("ROBUSTA_ANDROID_EXAMPLE", "threadTestWithClass IN: " + s);
+        return 10;
+    }
 
 }

robusta-android-example/src/lib.rs

@@ -1,14 +1,23 @@
+pub(crate) mod thread_func;
+
+use ::jni::objects::GlobalRef;
+use ::jni::JavaVM;
 use robusta_jni::bridge;
+use std::sync::OnceLock;
+
+static APP_CONTEXT: OnceLock<(JavaVM, GlobalRef)> = OnceLock::new();
 
 #[bridge]
 mod jni {
+    use crate::APP_CONTEXT;
     use android_logger::Config;
-    use jni::objects::JObject;
+    use jni::objects::{GlobalRef, JObject, JValue};
     use log::info;
     use robusta_jni::convert::{IntoJavaValue, Signature, TryFromJavaValue, TryIntoJavaValue};
     use robusta_jni::jni::errors::Result as JniResult;
     use robusta_jni::jni::objects::AutoLocal;
     use robusta_jni::jni::JNIEnv;
+    use std::thread;
 
     #[derive(Signature, TryIntoJavaValue, IntoJavaValue, TryFromJavaValue)]
     #[package(com.example.robustaandroidexample)]
@@ -24,14 +33,61 @@ mod jni {
                     .with_min_level(log::Level::Debug)
                     .with_tag("RUST_ROBUSTA_ANDROID_EXAMPLE"),
             );
+
+            info!("TEST START");
+            let java_class = env
+                .find_class("com/example/robustaandroidexample/RobustaAndroidExample")
+                .unwrap();
+            let _ = APP_CONTEXT.set((
+                env.get_java_vm().unwrap(),
+                env.new_global_ref(java_class).unwrap(),
+            ));
+
             let app_files_dir = RobustaAndroidExample::getAppFilesDir(env, context).unwrap();
             info!("App files dir: {}", app_files_dir);
+
+            assert_eq!(
+                RobustaAndroidExample::threadTestNoClass(env, "test".to_string()).unwrap(),
+                10
+            );
+
+            let test_string = env.new_string("SUPER TEST").unwrap();
+            let test_string = JValue::from(test_string);
+            let met_call = env.call_static_method(
+                "com/example/robustaandroidexample/RobustaAndroidExample",
+                "threadTestNoClass",
+                "(Ljava/lang/String;)I",
+                &[test_string],
+            );
+            assert!(met_call.is_ok());
+
+            let thread_handler = thread::Builder::new()
+                .name("test_thread_fail".to_string())
+                .spawn(move || crate::thread_func::thread_test_fail());
+            let join_res = thread_handler.unwrap().join().unwrap();
+            assert!(join_res.is_err());
+
+            let thread_handler = thread::Builder::new()
+                .name("test_thread_good".to_string())
+                .spawn(move || crate::thread_func::thread_test_good());
+            let join_res = thread_handler.unwrap().join().unwrap();
+            assert!(join_res.is_ok());
+
+            info!("TEST END");
         }
 
         pub extern "java" fn getAppFilesDir(
             env: &JNIEnv,
             #[input_type("Landroid/content/Context;")] context: JObject,
         ) -> JniResult<String> {
         }
+
+        pub extern "java" fn threadTestNoClass(env: &JNIEnv, s: String) -> JniResult<i32> {}
+        pub extern "java" fn threadTestWithClass(
+            env: &JNIEnv,
+            class_ref: &GlobalRef,
+            s: String,
+        ) -> JniResult<i32> {
+        }
     }
 }

robusta-android-example/src/thread_func.rs

@@ -0,0 +1,90 @@
+use crate::jni::RobustaAndroidExample;
+use jni::objects::JValue;
+use log::{debug, error};
+
+pub(crate) fn thread_test_fail() -> Result<(), String> {
+    debug!("TEST_THREAD_FAIL: start...");
+
+    let (app_vm, _) = crate::APP_CONTEXT
+        .get()
+        .ok_or_else(|| "Couldn't get APP_CONTEXT".to_string())?;
+    let env = app_vm
+        .attach_current_thread_permanently()
+        .map_err(|_| "Couldn't attach to current thread".to_string())?;
+
+    debug!("TEST_THREAD_FAIL: via JNI");
+    let test_string = env.new_string("SUPER TEST").unwrap();
+    let test_string = JValue::from(test_string);
+    if let Err(e) = env.call_static_method(
+        "com/example/robustaandroidexample/RobustaAndroidExample",
+        "threadTestNoClass",
+        "(Ljava/lang/String;)I",
+        &[test_string],
+    ) {
+        error!("Couldn't call method via classic JNI: {}", e);
+        if env.exception_check().unwrap_or(false) {
+            let _ = env.exception_clear();
+        }
+    }
+
+    debug!("TEST_THREAD_FAIL: via Robusta");
+
+    /* Call methode */
+    if let Err(e) = RobustaAndroidExample::threadTestNoClass(&env, "test".to_string()) {
+        let msg = format!("Couldn't call method via Robusta: {}", e);
+        error!("{}", msg);
+        if env.exception_check().unwrap_or(false) {
+            let _ = env.exception_clear();
+        }
+        return Err(msg);
+    }
+    Ok(())
+}
+
+pub(crate) fn thread_test_good() -> Result<(), String> {
+    debug!("TEST_THREAD_GOOD: start...");
+
+    let (app_vm, class_ref) = crate::APP_CONTEXT
+        .get()
+        .ok_or_else(|| "Couldn't get APP_CONTEXT".to_string())?;
+    let env = app_vm
+        .attach_current_thread_permanently()
+        .map_err(|_| "Couldn't attach to current thread".to_string())?;
+
+    debug!("TEST_THREAD_GOOD: via JNI");
+    let test_string = env.new_string("SUPER TEST").unwrap();
+    let test_string = JValue::from(test_string);
+    if let Err(e) = env.call_static_method(
+        class_ref,
+        "threadTestNoClass",
+        "(Ljava/lang/String;)I",
+        &[test_string],
+    ) {
+        error!("Couldn't call method via classic JNI: {}", e);
+        if env.exception_check().unwrap_or(false) {
+            let ex = env.exception_occurred().unwrap();
+            let _ = env.exception_clear();
+            let res = env
+                .call_method(ex, "toString", "()Ljava/lang/String;", &[])
+                .unwrap()
+                .l()
+                .unwrap();
+            let ex_msg: String = env.get_string(res.into()).unwrap().into();
+            error!("check_jni_error: {}", ex_msg);
+        }
+    }
+
+    debug!("TEST_THREAD_GOOD: via Robusta");
+
+    /* Call methode */
+    if let Err(e) = RobustaAndroidExample::threadTestWithClass(&env, class_ref, "test".to_string())
+    {
+        let msg = format!("Couldn't call method via Robusta: {}", e);
+        error!("{}", msg);
+        if env.exception_check().unwrap_or(false) {
+            let _ = env.exception_clear();
+        }
+        return Err(msg);
+    }
+    Ok(())
+}

robusta-codegen/src/transformation/imported.rs

@@ -10,7 +10,7 @@ use syn::{FnArg, ImplItemMethod, Lit, Pat, PatIdent, ReturnType, Signature};
 use crate::transformation::context::StructContext;
 use crate::transformation::utils::get_call_type;
 use crate::transformation::{CallType, CallTypeAttribute, SafeParams};
-use crate::utils::{get_abi, get_env_arg, is_self_method};
+use crate::utils::{get_abi, get_class_arg_if_any, get_env_arg, is_self_method};
 use std::collections::HashSet;
 
 pub struct ImportedMethodTransformer<'ctx> {
@@ -49,7 +49,8 @@ impl<'ctx> Fold for ImportedMethodTransformer<'ctx> {
 
                 let mut original_signature = node.sig.clone();
                 let self_method = is_self_method(&node.sig);
-                let (mut signature, env_arg) = get_env_arg(node.sig.clone());
+                let (signature, env_arg) = get_env_arg(node.sig.clone());
+                let (mut signature, class_ref_arg) = get_class_arg_if_any(signature.clone());
 
                 let impl_item_attributes: Vec<_> = {
                     let discarded_known_attributes: HashSet<&str> = {
@@ -321,6 +322,20 @@ impl<'ctx> Fold for ImportedMethodTransformer<'ctx> {
                     h
                 };
 
+                let class_arg_ident = if let Some(class_ref_arg) = class_ref_arg {
+                    match class_ref_arg {
+                        FnArg::Typed(t) => {
+                            match *t.pat {
+                                Pat::Ident(PatIdent { ident, .. }) => Some(ident),
+                                _ => panic!("non-ident pat in FnArg")
+                            }
+                        },
+                        _ => panic!("Bug -- please report to library author. Expected env parameter, found receiver")
+                    }
+                } else {
+                    None
+                };
+
                 original_signature.inputs.iter_mut().for_each(|i| match i {
                     FnArg::Typed(t) => match &*t.pat {
                         Pat::Ident(PatIdent { ident, .. }) if ident == "self" => {}
@@ -373,32 +388,64 @@ impl<'ctx> Fold for ImportedMethodTransformer<'ctx> {
                         match call_type {
                             CallType::Safe(_) => {
                                 if is_constructor {
-                                    parse_quote! {{
-                                        let env: &'_ ::robusta_jni::jni::JNIEnv<'_> = #env_ident;
-                                        let res = env.new_object(#java_class_path, #java_signature, &[#input_conversions]);
-                                        #return_expr
-                                    }}
+                                    if let Some(class_arg_ident) = class_arg_ident {
+                                        parse_quote! {{
+                                            let env: &'_ ::robusta_jni::jni::JNIEnv<'_> = #env_ident;
+                                            let res = env.new_object(#class_arg_ident, #java_signature, &[#input_conversions]);
+                                            #return_expr
+                                        }}
+                                    } else {
+                                        parse_quote! {{
+                                            let env: &'_ ::robusta_jni::jni::JNIEnv<'_> = #env_ident;
+                                            let res = env.new_object(#java_class_path, #java_signature, &[#input_conversions]);
+                                            #return_expr
+                                        }}
+                                    }
                                 } else {
-                                    parse_quote! {{
-                                        let env: &'_ ::robusta_jni::jni::JNIEnv<'_> = #env_ident;
-                                        let res = env.call_static_method(#java_class_path, #java_method_name, #java_signature, &[#input_conversions]);
-                                        #return_expr
-                                    }}
+                                    if let Some(class_arg_ident) = class_arg_ident {
+                                        parse_quote! {{
+                                            let env: &'_ ::robusta_jni::jni::JNIEnv<'_> = #env_ident;
+                                            let res = env.call_static_method(#class_arg_ident, #java_method_name, #java_signature, &[#input_conversions]);
+                                            #return_expr
+                                        }}
+                                    } else {
+                                        parse_quote! {{
+                                            let env: &'_ ::robusta_jni::jni::JNIEnv<'_> = #env_ident;
+                                            let res = env.call_static_method(#java_class_path, #java_method_name, #java_signature, &[#input_conversions]);
+                                            #return_expr
+                                        }}
+                                    }
                                 }
                             }
                             CallType::Unchecked(_) => {
                                 if is_constructor {
-                                    parse_quote! {{
-                                        let env: &'_ ::robusta_jni::jni::JNIEnv<'_> = #env_ident;
-                                        let res = env.new_object(#java_class_path, #java_signature, &[#input_conversions]).unwrap();
-                                        #return_expr
-                                    }}
+                                    if let Some(class_arg_ident) = class_arg_ident {
+                                        parse_quote! {{
+                                            let env: &'_ ::robusta_jni::jni::JNIEnv<'_> = #env_ident;
+                                            let res = env.new_object(#class_arg_ident, #java_signature, &[#input_conversions]).unwrap();
+                                            #return_expr
+                                        }}
+                                    } else {
+                                        parse_quote! {{
+                                            let env: &'_ ::robusta_jni::jni::JNIEnv<'_> = #env_ident;
+                                            let res = env.new_object(#java_class_path, #java_signature, &[#input_conversions]).unwrap();
+                                            #return_expr
+                                        }}
+                                    }
                                 } else {
-                                    parse_quote! {{
-                                        let env: &'_ ::robusta_jni::jni::JNIEnv<'_> = #env_ident;
-                                        let res = env.call_static_method(#java_class_path, #java_method_name, #java_signature, &[#input_conversions]).unwrap();
-                                        #return_expr
-                                    }}
+                                    if let Some(class_arg_ident) = class_arg_ident {
+                                        parse_quote! {{
+                                            let env: &'_ ::robusta_jni::jni::JNIEnv<'_> = #env_ident;
+                                            let res = env.call_static_method(#class_arg_ident, #java_method_name, #java_signature, &[#input_conversions]).unwrap();
+                                            #return_expr
+                                        }}
+                                    } else {
+                                        parse_quote! {{
+                                            let env: &'_ ::robusta_jni::jni::JNIEnv<'_> = #env_ident;
+                                            let res = env.call_static_method(#java_class_path, #java_method_name, #java_signature, &[#input_conversions]).unwrap();
+                                            #return_expr
+                                        }}
+                                    }
                                 }
                             }
                         }

robusta-codegen/src/utils.rs

@@ -95,6 +95,50 @@ pub fn get_env_arg(signature: Signature) -> (Signature, Option<FnArg>) {
     (transformed_signature, env_arg)
 }
 
+pub fn get_class_arg_if_any(signature: Signature) -> (Signature, Option<FnArg>) {
+    let has_explicit_class_ref_arg = if let Some(FnArg::Typed(PatType { ty, .. })) = signature.inputs.iter().next() {
+        if let Type::Reference(TypeReference { elem, .. }) = &**ty {
+            if let Type::Path(t) = &**elem {
+                let full_path: Path = parse_quote! { ::robusta_jni::jni::objects::GlobalRef };
+                let imported_path: Path = parse_quote! { GlobalRef };
+                let canonicalized_type_path = canonicalize_path(&t.path);
+
+                canonicalized_type_path == imported_path || canonicalized_type_path == full_path
+            } else {
+                false
+            }
+        } else if let Type::Path(t) = &**ty {
+            /* If the user has input `class_ref: GlobalRef` instead of `class_ref: &GlobalRef`, we let them know. */
+            let full_path: Path = parse_quote! { ::robusta_jni::jni::objects::GlobalRef };
+            let imported_path: Path = parse_quote! { GlobalRef };
+            let canonicalized_type_path = canonicalize_path(&t.path);
+
+            if canonicalized_type_path == imported_path || canonicalized_type_path == full_path {
+                emit_error!(t, "explicit environment parameter must be of type `&GlobalRef`");
+            }
+
+            false
+        } else {
+            false
+        }
+    } else {
+        false
+    };
+
+    if has_explicit_class_ref_arg {
+        let mut inner_signature = signature;
+
+        let mut iter = inner_signature.inputs.into_iter();
+        let class_arg = iter.next();
+
+        inner_signature.inputs = iter.collect();
+        (inner_signature, class_arg)
+
+    } else {
+        (signature, None)
+    }
+}
+
 pub fn get_abi(sig: &Signature) -> Option<String> {
     sig.abi
         .as_ref()