feat: event stream (hgs watch) and the desktop consumer (event data plane M3+M4)

.github/dependabot.yml

@@ -14,7 +14,7 @@ updates:
         applies-to: security-updates
         patterns: ["*"]
   - package-ecosystem: cargo
-    directories: ["/", "/services/mobile/relay", "/services/mobile/connector", "/crates/replica", "/crates/replica-ffi"]
+    directories: ["/", "/services/mobile/relay", "/services/mobile/connector", "/crates/replica", "/crates/replica-ffi", "/crates/watch-protocol"]
     schedule:
       interval: monthly
     open-pull-requests-limit: 1

.github/workflows/checks.yml

@@ -160,6 +160,11 @@ jobs:
           cargo +1.99.1 fmt --check --manifest-path crates/replica-ffi/Cargo.toml
           cargo +1.99.1 clippy --locked --manifest-path crates/replica-ffi/Cargo.toml --target-dir target/replica-ffi --all-targets -- -D warnings
           cargo +1.99.1 test --locked --manifest-path crates/replica-ffi/Cargo.toml --target-dir target/replica-ffi
+      - name: Watch protocol crate (format, lints, tests)
+        run: |
+          cargo +1.99.1 fmt --check --manifest-path crates/watch-protocol/Cargo.toml
+          cargo +1.99.1 clippy --locked --manifest-path crates/watch-protocol/Cargo.toml --target-dir target/watch-protocol --all-targets -- -D warnings
+          cargo +1.99.1 test --locked --manifest-path crates/watch-protocol/Cargo.toml --target-dir target/watch-protocol
       # Packages fail without a notice for every shipped crate; find out here.
       - name: Rust license notices
         run: python3 scripts/collect-licenses.py "$RUNNER_TEMP/rust-licenses"

CONTRIBUTING.md

@@ -70,6 +70,8 @@ stable release, and raising them is routine maintenance. Run
 The replica crate has its own lockfile: run
 `cargo +1.99.1 test --locked --manifest-path crates/replica/Cargo.toml`; its
 golden vectors must keep decoding, and `ZERUS_BLESS=1` only adds new ones.
+The event stream's frame crate has one too: run
+`cargo +1.99.1 test --locked --manifest-path crates/watch-protocol/Cargo.toml --target-dir target/watch-protocol`.
 
 On Linux, the three worktree modules run through `scripts/ci/worktree-tests.py`
 in a fresh PID/mount namespace, including their live process blockers and private
@@ -110,6 +112,16 @@ class) and before it starts.
 `CHILD_PROCESS_EXEMPT` in the script names the files that may start children
 otherwise, each with its reason.
 
+The desktop parses JSON only through [JsonParse.h](tray/src/JsonParse.h), off
+the GUI thread: `hgs` output in a `ProcessRunner` prepare step, other data
+through `ProcessRunner::post` or an existing worker, and QSettings values
+through `SettingsJson`. `check-source.py` rejects `QJsonDocument::fromJson` in
+`tray/src` outside `JsonParse.cpp`, and lists the files that may still call
+`JsonParse::local()` on the GUI thread and how often; that list only shrinks.
+Every Qt suite runs with `ZERUS_GUI_THREAD_CHECKS=fatal`, so a parse on the GUI
+thread aborts the test with its call site. A GUI suite that checks a parser
+directly calls it through `offGuiThread()` (`tray/tests/support/OffGuiThread.h`).
+
 A change to tmux or `ps` call sites must keep Unix behaviour unchanged: compare a
 [tmux census](docs/ci-and-aur.md#unix-tmux-census) of the branch with one of main.
 `scripts/ci/check-windows-target.sh` type-checks the Windows target from Linux or

Cargo.toml

@@ -34,6 +34,7 @@ toml_edit = "0.25"
 unicode-width = "0.2"
 uuid = { version = "1", features = ["v4"] }
 zerus-replica = { path = "crates/replica" }
+zerus-watch-protocol = { path = "crates/watch-protocol" }
 
 [target.'cfg(windows)'.dependencies]
 windows-sys = { version = "0.61", features = [

crates/watch-protocol/.cargo/config.toml

@@ -0,0 +1,2 @@
+[resolver]
+incompatible-rust-versions = "fallback"

crates/watch-protocol/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "zerus-watch-protocol"
+version = "0.1.0"
+edition = "2021"
+rust-version = "1.99"
+license = "MIT"
+description = "Frames and control operations of the hgs watch event stream (watch-v1)"
+publish = false
+
+# Shared by hgs and its clients. Keep it to serde: no Loro, Qt or async runtime.
+[dependencies]
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"