[fp-rs] Added custom FP error type to Rust code.

fastpair/rust/bluetooth/src/common/address.rs

@@ -134,7 +134,7 @@ mod tests {
     fn try_from_ble_address_to_classic() {
         let ble_addr = BleAddress::new(0x112233445566, BleAddressKind::Public);
         let result: Result<ClassicAddress, BluetoothError> =
-            TryFrom::try_from(ble_addr);
+            ble_addr.try_into();
         assert!(result.is_ok());
         assert_eq!(result.unwrap().0, [0x66, 0x55, 0x44, 0x33, 0x22, 0x11]);
 

fastpair/rust/bluetooth/src/common/advertisement.rs

@@ -18,7 +18,7 @@ use super::{BleAddress, BluetoothError};
 /// information about the advertisement (e.g. address of sender) as well as
 /// data sections extracted from the advertisement. Platform-specific methods
 /// should be written to load in data sections from incoming advertisements.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct BleAdvertisement {
     address: BleAddress,
     rssi: Option<DecibelMilliwatts>,

fastpair/rust/demo/lib/bridge_definitions.dart

@@ -1,17 +1,3 @@
-// Copyright 2023 Google LLC
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
 // AUTO GENERATED FILE, DO NOT EDIT.
 // Generated by `flutter_rust_bridge`@ 1.79.0.
 // ignore_for_file: non_constant_identifier_names, unused_element, duplicate_ignore, directives_ordering, curly_braces_in_flow_control_structures, unnecessary_lambdas, slash_for_doc_comments, prefer_const_literals_to_create_immutables, implicit_dynamic_list_literal, duplicate_import, unused_import, unnecessary_import, prefer_single_quotes, prefer_const_constructors, use_super_parameters, always_use_package_imports, annotate_overrides, invalid_use_of_protected_member, constant_identifier_names, invalid_use_of_internal_member, prefer_is_empty, unnecessary_const

fastpair/rust/demo/lib/bridge_generated.dart

@@ -1,17 +1,3 @@
-// Copyright 2023 Google LLC
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
 // AUTO GENERATED FILE, DO NOT EDIT.
 // Generated by `flutter_rust_bridge`@ 1.79.0.
 // ignore_for_file: non_constant_identifier_names, unused_element, duplicate_ignore, directives_ordering, curly_braces_in_flow_control_structures, unnecessary_lambdas, slash_for_doc_comments, prefer_const_literals_to_create_immutables, implicit_dynamic_list_literal, duplicate_import, unused_import, unnecessary_import, prefer_single_quotes, prefer_const_constructors, use_super_parameters, always_use_package_imports, annotate_overrides, invalid_use_of_protected_member, constant_identifier_names, invalid_use_of_internal_member, prefer_is_empty, unnecessary_const

fastpair/rust/demo/rust/Cargo.toml

@@ -9,7 +9,6 @@ edition = "2021"
 crate-type = ["lib", "cdylib", "staticlib"]
 
 [dependencies]
-anyhow = "1.0"
 bluetooth = { version = "0.1", path = "../../bluetooth" }
 flutter_rust_bridge = "1"
 futures = { version = "0.3", features = ["executor"] }
@@ -17,3 +16,4 @@ serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 tracing = "0.1.37"
 ttl_cache = "0.5.1"
+thiserror = "1.0.43"

fastpair/rust/demo/rust/src/advertisement.rs

@@ -14,14 +14,14 @@
 
 use bluetooth::{BleAddress, BleAdvertisement, ServiceData};
 
-use crate::{decoder::FpDecoder, fetcher::FpFetcher};
+use crate::{decoder::FpDecoder, error::FpError, fetcher::FpFetcher};
 
 /// Represents a FP device model ID.
 pub(crate) type ModelId = String;
 
 /// Holds information required to make decisions about an incoming Fast Pair
 /// advertisement.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub(crate) struct FpPairingAdvertisement {
     inner: BleAdvertisement,
     /// Estimated distance in meters of device from BLE adapter.
@@ -37,13 +37,15 @@ impl FpPairingAdvertisement {
         adv: BleAdvertisement,
         service_data: &ServiceData<u16>,
         fetcher: &Box<dyn FpFetcher>,
-    ) -> Result<Self, anyhow::Error> {
-        let rssi = adv.rssi().ok_or(anyhow::anyhow!(
-            "Windows advertisements should contain RSSI information."
-        ))?;
-        let tx_power = adv.tx_power().ok_or(anyhow::anyhow!(
-            "Fast Pair advertisements should advertise their transmit power."
-        ))?;
+    ) -> Result<Self, FpError> {
+        let rssi = adv.rssi().ok_or(FpError::ContractViolation(String::from(
+            "Windows advertisements should contain RSSI information.",
+        )))?;
+        let tx_power = adv
+            .tx_power()
+            .ok_or(FpError::ContractViolation(String::from(
+                "Windows advertisements should contain RSSI information.",
+            )))?;
 
         let distance = distance_from_rssi_and_tx_power(rssi, tx_power);
 
@@ -51,22 +53,16 @@ impl FpPairingAdvertisement {
         // data in the `FpPairingAdvertisement` since it's easily accessible from
         // `FpPairingAdvertisement.inner`, but it's convenient to save the parsed
         // model ID.
-        let mut model_id =
-            FpDecoder::get_model_id_from_service_data(service_data).or_else(|err| {
-                // Some FP advertisements can be GATT non-discoverable
-                // advertisements containing service data that isn't
-                // the device model ID. In this case, simply ignore
-                // advertisements with errors extracting the model ID.
-                // See: developers.google.com/nearby/fast-pair/specifications/service/provider
-                Err(anyhow::anyhow!("error extracting model ID: {}", err))
-            })?;
+        let mut model_id = FpDecoder::get_model_id_from_service_data(service_data)?;
 
         if model_id.len() != 3 {
             // In this demo of Fast Pair Rust, only model ID's
             // of length 3 bytes are supported. Therefore, if a
             // larger model ID makes it this far, log an error.
             // TODO b/294453912
-            return Err(anyhow::anyhow!("Error: model ID of unsupported length"));
+            return Err(FpError::Internal(String::from(
+                "creating `model_id` should have already failed",
+            )));
         }
 
         // Pad with 0 at the beginning to successfully call `from_be_bytes`.
@@ -193,6 +189,7 @@ mod tests {
         let fp_adv = FpPairingAdvertisement::new(ble_adv, &service_data, &fetcher);
 
         assert!(fp_adv.is_err());
+        assert!(matches!(fp_adv.unwrap_err(), FpError::ContractViolation(_)));
     }
 
     #[test]
@@ -212,25 +209,7 @@ mod tests {
         let fp_adv = FpPairingAdvertisement::new(ble_adv, &service_data, &fetcher);
 
         assert!(fp_adv.is_err());
-    }
-
-    #[test]
-    fn test_new_fp_pairing_advertisement_bad_service_data() {
-        let addr = BleAddress::new(0x112233, BleAddressKind::Public);
-        let ble_adv = BleAdvertisement::new(addr, Some(-60), Some(10));
-
-        let raw_data = vec![4, 3, 2, 1];
-        let service_data = ServiceData::new(0x123 as u16, raw_data);
-
-        let device_info = Ok(DeviceInfo::new(
-            String::from("image_url"),
-            String::from("name"),
-        ));
-        let fetcher: Box<dyn FpFetcher> = Box::new(FpFetcherMock::new(device_info));
-
-        let fp_adv = FpPairingAdvertisement::new(ble_adv, &service_data, &fetcher);
-
-        assert!(fp_adv.is_err());
+        assert!(matches!(fp_adv.unwrap_err(), FpError::ContractViolation(_)));
     }
 
     #[test]
@@ -241,12 +220,11 @@ mod tests {
         let raw_data = vec![3, 2, 1];
         let service_data = ServiceData::new(0x123 as u16, raw_data);
 
-        let fetcher: Box<dyn FpFetcher> = Box::new(FpFetcherMock::new(Err(anyhow::anyhow!(
-            "mock intentional error"
-        ))));
+        let fetcher: Box<dyn FpFetcher> = Box::new(FpFetcherMock::new(Err(FpError::Test)));
 
         let fp_adv = FpPairingAdvertisement::new(ble_adv, &service_data, &fetcher);
 
         assert!(fp_adv.is_err());
+        assert!(matches!(fp_adv.unwrap_err(), FpError::Test));
     }
 }

fastpair/rust/demo/rust/src/api.rs

@@ -160,10 +160,9 @@ pub fn init() {
 }
 
 /// Sets up `StreamSink` for Dart-Rust FFI.
-pub fn event_stream(s: StreamSink<Option<[String; 2]>>) -> Result<(), anyhow::Error> {
+pub fn event_stream(s: StreamSink<Option<[String; 2]>>) {
     let mut stream = DEVICE_STREAM.write().unwrap();
     *stream = Some(s);
-    Ok(())
 }
 
 /// Attempt classic pairing with currently displayed device.

fastpair/rust/demo/rust/src/bridge_generated.rs

@@ -54,7 +54,11 @@ fn wire_event_stream_impl(port_: MessagePort) {
             mode: FfiCallMode::Stream,
         },
         move || {
-            move |task_callback| event_stream(task_callback.stream_sink::<_, Option<[String; 2]>>())
+            move |task_callback| {
+                Ok(event_stream(
+                    task_callback.stream_sink::<_, Option<[String; 2]>>(),
+                ))
+            }
         },
     )
 }

fastpair/rust/demo/rust/src/decoder.rs

@@ -13,6 +13,8 @@
 // limitations under the License.
 use bluetooth::ServiceData;
 
+use crate::error::FpError;
+
 /// Unit struct providing parsing operations for Fast Pair advertisements.
 pub(crate) struct FpDecoder;
 
@@ -25,13 +27,13 @@ impl FpDecoder {
     /// Currently unavailable in Fast Pair devices and not supported.
     pub(crate) fn get_model_id_from_service_data<U: Copy>(
         service_data: &ServiceData<U>,
-    ) -> Result<Vec<u8>, anyhow::Error> {
+    ) -> Result<Vec<u8>, FpError> {
         static MIN_MODEL_ID_LENGTH: usize = 3;
         let data = service_data.data();
 
         if data.len() < MIN_MODEL_ID_LENGTH {
             // If service data too small, invalid payload.
-            Err(anyhow::anyhow!(format!(
+            Err(FpError::ContractViolation(format!(
                 "Invalid model ID for Fast Pair advertisement of length {}.",
                 data.len()
             )))
@@ -41,13 +43,14 @@ impl FpDecoder {
         } else {
             // Else, this Fast Pair advertisement is currently unsupported.
             // b/294453912
-            Err(anyhow::anyhow!(
-                "This Fast Pair device is currently unsupported."
-            ))
+            Err(FpError::NotImplemented(String::from(
+                "This Fast Pair device is currently unsupported.",
+            )))
         }
     }
 }
 
+#[cfg(test)]
 mod tests {
     use super::*;
 
@@ -70,6 +73,7 @@ mod tests {
         let service_data = ServiceData::new(uuid, data);
         let result = FpDecoder::get_model_id_from_service_data(&service_data);
         assert!(result.is_err());
+        assert!(matches!(result.unwrap_err(), FpError::ContractViolation(_)));
     }
 
     #[test]
@@ -80,5 +84,6 @@ mod tests {
         let service_data = ServiceData::new(uuid, data);
         let result = FpDecoder::get_model_id_from_service_data(&service_data);
         assert!(result.is_err());
+        assert!(matches!(result.unwrap_err(), FpError::NotImplemented(_)));
     }
 }

fastpair/rust/demo/rust/src/error.rs

@@ -0,0 +1,43 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use thiserror::Error;
+
+/// Library error type.
+#[non_exhaustive]
+#[derive(Error, Debug, PartialEq, Clone)]
+pub enum FpError {
+    /// Reported when a requested resource could not be accessed, either because
+    /// it's missing or because the user lacks access permissions.
+    #[error("not found: {0}")]
+    AccessDenied(String),
+    /// Reported when Fast Pair functionality does not behave according to the
+    /// specification. For example, advertisement packets with invalid lengths,
+    /// JSON data with bad formatting, etc.
+    #[error("contract violation: {0}")]
+    ContractViolation(String),
+    /// Reported when trying to invoke Fast Pair functionality that is currently
+    /// not implemented.
+    #[error("feature not implemented: {0}")]
+    NotImplemented(String),
+    /// Reported when a bug occurs inside the library. Whenever a seemingly
+    /// impossible error condition arises where you could call `expect()`,
+    /// return this error instead.
+    #[error("internal error: {0}")]
+    Internal(String),
+    /// Reported when an error was intentionally raised by test code.
+    #[error("intentional error")]
+    #[cfg(test)]
+    Test,
+}

fastpair/rust/demo/rust/src/fetcher/common.rs

@@ -14,15 +14,12 @@
 
 use serde::Deserialize;
 
-use crate::advertisement::ModelId;
+use crate::{advertisement::ModelId, error::FpError};
 
 /// Types that can fetch Fast Pair data from external storage (e.g. filesystem,
 /// remote server).
 pub(crate) trait FpFetcher {
-    fn get_device_info_from_model_id(
-        &self,
-        model_id: &ModelId,
-    ) -> Result<DeviceInfo, anyhow::Error>;
+    fn get_device_info_from_model_id(&self, model_id: &ModelId) -> Result<DeviceInfo, FpError>;
 }
 
 /// Holds Fast Pair device information parsed from JSON.

fastpair/rust/demo/rust/src/fetcher/fs.rs

@@ -16,6 +16,7 @@ use std::fs;
 
 use crate::{
     advertisement::ModelId,
+    error::FpError,
     fetcher::{DeviceInfo, FpFetcher, JsonData},
 };
 
@@ -35,14 +36,13 @@ impl FpFetcher for FpFetcherFs {
     /// this information is saved locally. In the future, this should instead
     /// be retrieved from a remote server and cached.
     /// b/294456411
-    fn get_device_info_from_model_id(
-        &self,
-        model_id: &ModelId,
-    ) -> Result<DeviceInfo, anyhow::Error> {
+    fn get_device_info_from_model_id(&self, model_id: &ModelId) -> Result<DeviceInfo, FpError> {
         let file_path = format!("{}/{}.json", self.path, model_id);
-        let contents = fs::read_to_string(file_path).expect("Couldn't find or open file.");
+        let contents = fs::read_to_string(file_path)
+            .or_else(|err| Err(FpError::AccessDenied(err.to_string())))?;
 
-        let model_info: JsonData = serde_json::from_str(&contents)?;
+        let model_info: JsonData = serde_json::from_str(&contents)
+            .or_else(|err| Err(FpError::ContractViolation(err.to_string())))?;
 
         Ok(model_info.device())
     }

fastpair/rust/demo/rust/src/fetcher/mock.rs

@@ -14,30 +14,25 @@
 
 use crate::{
     advertisement::ModelId,
+    error::FpError,
     fetcher::{DeviceInfo, FpFetcher},
 };
 
 /// A struct for mocking retrieval of Fast Pair data.
 pub(crate) struct FpFetcherMock {
-    get_device_info_from_model_id: Result<DeviceInfo, anyhow::Error>,
+    device_info_from_model_id: Result<DeviceInfo, FpError>,
 }
 
 impl FpFetcherMock {
-    pub(crate) fn new(get_device_info_from_model_id: Result<DeviceInfo, anyhow::Error>) -> Self {
+    pub(crate) fn new(device_info_from_model_id: Result<DeviceInfo, FpError>) -> Self {
         FpFetcherMock {
-            get_device_info_from_model_id,
+            device_info_from_model_id,
         }
     }
 }
 
 impl FpFetcher for FpFetcherMock {
-    fn get_device_info_from_model_id(
-        &self,
-        _model_id: &ModelId,
-    ) -> Result<DeviceInfo, anyhow::Error> {
-        match &self.get_device_info_from_model_id {
-            Ok(result) => Ok(result.clone()),
-            Err(_) => Err(anyhow::anyhow!("intentional mock error")),
-        }
+    fn get_device_info_from_model_id(&self, _model_id: &ModelId) -> Result<DeviceInfo, FpError> {
+        self.device_info_from_model_id.clone()
     }
 }

fastpair/rust/demo/rust/src/lib.rs

@@ -16,4 +16,5 @@ mod advertisement;
 mod api;
 mod bridge_generated; /* AUTO INJECTED BY flutter_rust_bridge. This line may not be accurate, and you can change it according to your needs. */
 mod decoder;
+mod error;
 mod fetcher;

fastpair/rust/demo/windows/flutter/generated_plugin_registrant.cc

@@ -1,24 +1,10 @@
-// Copyright 2023 Google LLC
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
 //
 //  Generated file. Do not edit.
 //
 
 // clang-format off
 
-#include "./generated_plugin_registrant.h"
+#include "generated_plugin_registrant.h"
 
 
 void RegisterPlugins(flutter::PluginRegistry* registry) {

fastpair/rust/demo/windows/flutter/generated_plugin_registrant.h

@@ -1,17 +1,3 @@
-// Copyright 2023 Google LLC
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
 //
 //  Generated file. Do not edit.
 //