[coverage] initial implementation

python/tryke/coverage.py

@@ -0,0 +1,39 @@
+"""Code coverage logic
+
+https://docs.python.org/3/library/sys.monitoring.html
+"""
+
+import sys
+from types import CodeType
+from typing import Final
+
+mon = sys.monitoring
+TOOL_ID = mon.COVERAGE_ID
+TOOL_NAME: Final = "tryke"
+
+type HitLocation = tuple[
+    # Path name
+    str,
+    # Line number
+    int,
+]
+
+
+class Coverage:
+    def __init__(self) -> None:
+        self._hits: set[HitLocation] = set()
+
+    def register(self) -> None:
+        existing_tool = mon.get_tool(TOOL_ID)
+        if existing_tool:
+            if existing_tool != TOOL_NAME:
+                msg = f"Unexpected existing tool: {existing_tool}"
+                raise ValueError(msg)
+        else:
+            mon.use_tool_id(TOOL_ID, TOOL_NAME)
+            mon.register_callback(TOOL_ID, mon.events.LINE, self._line_callback)
+            mon.set_events(TOOL_ID, mon.events.LINE)
+
+    def _line_callback(self, code: CodeType, line_number: int) -> object:
+        self._hits.add((code.co_filename, line_number))
+        return mon.DISABLE

python/tryke/worker.py

@@ -66,6 +66,7 @@
 from typing import TYPE_CHECKING, Literal, NotRequired, TypedDict
 
 import tryke_guard
+from tryke.coverage import Coverage
 from tryke.expect import (
     CaseArgs,
     CasesMarked,
@@ -104,9 +105,6 @@
 _log = logging.getLogger("tryke.worker")
 
 
-# -- Wire-format TypedDicts (mirror crates/tryke_runner/src/protocol.rs) ------
-
-
 class _AssertionWire(TypedDict):
     expression: str
     expected: str
@@ -363,8 +361,14 @@ def __init__(
         self._hook_metadata: dict[str, list[object]] = {}
         # Hook executors cached per module.
         self._executors: dict[str, HookExecutor] = {}
+        self._coverage: Coverage | None = None
 
     def run(self) -> None:
+        # TODO(thejchap): driven by config  # noqa: FIX002, TD003
+        if True:
+            self._coverage = Coverage()
+            self._coverage.register()
+
         for raw in self._input:
             line = raw.strip()
             if not line:

tests/test_coverage.py

@@ -0,0 +1,6 @@
+from tryke import expect, test
+
+
+@test(name="coverage")
+def test_coverage() -> None:
+    expect("a", "a is truthy").to_be_truthy()