16 KiB
Developer on boarding
Introduction
This doc is a quick introduction about the project and its architecture.
It's aim is to help new developers to understand the overall project and where to start developing.
Other useful documentation:
- all the docs in this folder!
- the contributing doc, that you should also read carefully.
Quick introduction to Matrix
Matrix website: matrix.org, discover page. Note: Matrix.org is also hosting a homeserver (.well-known file). The reference homeserver (this is how Matrix servers are called) implementation is Synapse. But other implementations exist. The Matrix specification is here to ensure that any Matrix client, such as Element Android and its SDK can talk to any Matrix server.
Have a quick look to the client-server API documentation: Client-server documentation. Other network API exist, the list is here: (https://spec.matrix.org/latest/)
Matrix is an open source protocol. Change are possible and are tracked using this GitHub repository. Changes to the protocol are called MSC: Matrix Spec Change. These are PullRequest to this project.
Matrix object are Json data. Unstable prefixes must be used for Json keys when the MSC is not merged (i.e. accepted).
Matrix data
There are many object and data in the Matrix worlds. Let's focus on the most important and used, Room
and Event
Room
Room
is a place which contains ordered Event
s. They are identified with their room_id
. Nearly all the data are stored in rooms, and shared using
homeserver to all the Room Member.
Note: Spaces are also Rooms with a different type
.
Event
Events
are items of a Room, where data is embedded.
There are 2 types of Room Event:
- Regular Events: contain useful content for the user (message, image, etc.), but are not necessarily displayed as this in the timeline (reaction, message edition, call signaling).
- State Events: contain the state of the Room (name, topic, etc.). They have a non null value for the key
state_key
.
Also all the Room Member details are in State Events: one State Event per member. In this case, the state_key
is the matrixId (= userId).
Important Fields of an Event:
event_id
: unique across the Matrix universe;room_id
: the room the Event belongs to;type
: describe what the Event contain, especially in thecontent
section, and how the SDK should handle this Event;content
: dynamic Event data; depends on thetype
.
So we have a triple event_id
, type
, state_key
which uniquely defines an Event.
Sync
This is managed by the Rust SDK.
Rust SDK
The Rust SDK is hosted here : https://github.com/matrix-org/matrix-rust-sdk This repository contains an implementation of a Matrix client-server library in Rust. With some bindings we can embedded this sdk inside other environments, like like Swift or Kotlin, with the help of Uniffi From these kotlin bindings we can generate native libs (.so files) and kotlin classes/interfaces.
To use these bindings in an android project, we need to wrap this up into an android library (as the form of an .aar file).
This is the goal of https://github.com/matrix-org/matrix-rust-components-kotlin
This repository is used for distributing kotlin releases of the Matrix Rust SDK.
It'll provide the corresponding aar and also publish them on maven.
Most of the time you want to use the releases made on maven with gradle implementation("org.matrix.rustcomponents:sdk-android:latest-version")
You can also have access to the aars through the release page.
If you need to locally build the sdk-android you can use the build script.
For this, you first need to ensure to setup :
- rust environment (check https://rust-lang.github.io/rustup/ if needed)
- cargo-ndk < 2.12.0
cargo install cargo-ndk --version 2.11.0
- android targets
rustup target add \ aarch64-linux-android \ armv7-linux-androideabi \ x86_64-linux-android \ i686-linux-android
- checkout both matrix-rust-sdk and matrix-rust-components-kotlin repositories
Then you can launch the build script with the following params:
-p Local path to the rust-sdk repository -o Optional output path with the expected name of the aar file. By default the aar will be located in the corresponding build/outputs/aar directory. -r Flag to build in release mode -m Option to select the gradle module to build. Default is sdk. -t Option to to select an android target to build against. Default will build for all targets.
So for example to build the sdk against aarch64-linux-android target and copy the generated aar to ElementX project:
./scripts/build.sh -p matrix-rust-sdk-path -t aarch64-linux-android -o element-x-android-path/libraries/rustsdk/matrix-rust-sdk.aar
Finally let the matrix/impl
module use this aar by switching those lines in the gradle file :
dependencies {
api(projects.libraries.rustsdk)
// api(libs.matrix.sdk)
...
}
You are good to test your local rust development now!
The Android project
The project should compile out of the box.
This Android project is a multi modules project.
app
module is the Android application module. Other modules are libraries;features
modules contain some UI and can be seen as screen or flow of screens of the application;libraries
modules contain classes that can be useful for other modules to work.
A few details about some modules:
libraries-core
module contains utility classes;libraries-designsystem
module contains Composables which can be used across the app (theme, etc.);libraries-elementresources
module contains resource from Element Android (mainly strings);libraries-matrix
module contains wrappers around the Matrix Rust SDK.
Most of the time a feature module should not know anything about other feature module.
The navigation glue is currently done in the app
module.
Here is the current module dependency graph:
Application
This Android project mainly handle the application layer of the whole software. The communication with the Matrix server, as well as the local storage, the cryptography (encryption and decryption of Event, key management, etc.) is managed by the Rust SDK.
The application is responsible to store the session credentials though.
Jetpack Compose
Compose is essentially two libraries : Compose Compiler and Compose UI. The compiler (and his runtime) is actually not specific to UI at all and offer powerful state management APIs. See https://jakewharton.com/a-jetpack-compose-by-any-other-name/
Some useful links:
- https://developer.android.com/jetpack/compose/mental-model
- https://developer.android.com/jetpack/compose/libraries
- https://developer.android.com/jetpack/compose/modifiers-list
- https://android.googlesource.com/platform/frameworks/support/+/androidx-main/compose/docs/compose-api-guidelines.md#api-guidelines-for-jetpack-compose
About Preview
Global architecture
Main libraries and frameworks used in this application:
- Navigation state with Appyx. Please watch this video to learn more about Appyx!
- DI: Dagger and Anvil
- Reactive State management with Compose runtime and Molecule
Some patterns are inspired by Circuit
Here are the main points:
Presenter
andView
does not communicate with each other directly, but throughState
andEvent
- Views are compose first
- Presenters are also compose first, and have a single
present(): State
method. It's using the power of compose-runtime/compiler. - The point of connection between a
View
and aPresenter
is aNode
. - A
Node
is also responsible for managing Dagger components if any. - A
ParentNode
has some childrenNode
and only know about them. - This is a single activity full compose application. The
MainActivity
is responsible for holding and configuring theRootNode
. - There is no more needs for Android Architecture Component ViewModel as configuration change should be handled by Composable if needed.
Template and naming
There is a template module to easily start a new feature. When creating a new module, you can just copy paste the template. It is located here.
For the naming rules, please follow what is being currently used in the template module.
Note that naming of files and classes is important, since those names are used to set up code coverage rules. For instance, presenters MUST have a
suffix Presenter
,states MUST have a suffix State
, etc. Also we want to have a common naming along all the modules.
Push
Note Firebase Push is not yet implemented on the project.
Please see the dedicated documentation for more details.
This is the classical scenario:
- App receives a Push. Note: Push is ignored if app is in foreground;
- App asks the SDK to load Event data (fastlane mode). We have a change to get the data faster and display the notification faster;
- App asks the SDK to perform a sync request.
Dependencies management
We are using Gradle version catalog on this project.
All the dependencies (including android artifact, gradle plugin, etc.) should be declared in ../gradle/libs.versions.toml file.
Some dependency, mainly because they are not shared can be declared in build.gradle.kts
files.
Dependabot is set up on the project. This tool will automatically create Pull Request to upgrade our dependencies one by one. Note Dependabot does not support yet Gradle version catalog. This is tracked by this issue.
Test
We have 3 tests frameworks in place, and this should be sufficient to guarantee a good code coverage and limit regressions hopefully:
- Maestro to test the global usage of the application. See the related documentation.
- Combination of Showkase and Paparazzi, to test UI pixel perfect. To add test,
just add
@Preview
for the composable you are adding. See the related documentation and see in the template the file TemplateView.kt. We create PreviewProvider to provide different states. See for instance the file TemplateStateProvider.kt- Tests on presenter with Molecule and Turbine. See in the template the class TemplatePresenterTests.
Note For now we want to avoid using class mocking (with library such as mockk), because this should be not necessary. We prefer to create Fake
implementation of our interfaces. Mocking can be used to mock Android framework classes though, such as Bitmap
for instance.
Code coverage
kover is used to compute code coverage. Only have unit tests can produce code coverage result. Running Maestro does not participate to the code coverage results.
Kover configuration is defined in the main build.gradle.kts file.
To compute the code coverage, run:
./gradlew koverMergedReport
and open the Html report: ../build/reports/kover/merged/html/index.html
To ensure that the code coverage threshold are OK, you can run
./gradlew koverMergedVerify
Note that the CI performs this check on every pull requests.
Also, if the rule Global minimum code coverage.
is in error because code coverage is > maxValue
, minValue
and maxValue
can be updated for this rule in
the file build.gradle.kts (you will see further instructions there).
Other points
Logging
**Important warning: ** NEVER log private user data, or use the flag LOG_PRIVATE_DATA
. Be very careful when logging data class
, all the content will be
output!
Timber is used to log data to logcat. We do not use directly the Log
class. If possible please use a tag, as per
Timber.tag(loggerTag.value).d("my log")
because automatic tag (= class name) will not be available on the release version.
Also generally it is recommended to provide the Throwable
to the Timber log functions.
Last point, note that Timber.v
function may have no effect on some devices. Prefer using Timber.d
and up.
Rageshake
Rageshake is a feature to send bug report directly from the application. Just shake your phone and you will be prompted to send a bug report.
Bug reports can contain:
- a screenshot of the current application state
- the application logs from up to 15 application starts
- the logcat logs
The data will be sent to an internal server, which is not publicly accessible. A GitHub issue will also be created to a private GitHub repository.
Rageshake can be very useful to get logs from a release version of the application.
Tips
- Element Android has a
developer mode
in theSettings/Advanced settings
. Other useful options are available here; (TODO Not supported yet!) - Show hidden Events can also help to debug feature. When developer mode is enabled, it is possible to view the source (= the Json content) of any Events; (TODO Not supported yet!)
- Type
/devtools
in a Room composer to access a developer menu. There are some other entry points. Developer mode has to be enabled; (TODO Not supported yet!) - Hidden debug menu: when developer mode is enabled and on debug build, there are some extra screens that can be accessible using the green wheel. In those screens, it will be possible to toggle some feature flags; (TODO Not supported yet!)
- Using logcat, filtering with
Compositions
can help you to understand what screen are currently displayed on your device. Searching for string displayed on the screen can also help to find the running code in the codebase. - When this is possible, prefer using
sealed interface
instead ofsealed class
; - When writing temporary code, using the string "DO NOT COMMIT" in a comment can help to avoid committing things by mistake. If committed and pushed, the CI will detect this String and will warn the user about it. (TODO Not supported yet!)
Happy coding!
The team is here to support you, feel free to ask anything to other developers.
Also please feel free to update this documentation, if incomplete/wrong/obsolete/etc.
Thanks!