feat: print a report (#2)

* print a report

* add asciinema

* update test

* fix

Author: alexeagle

.github/workflows/ci.yaml

@@ -26,7 +26,7 @@ jobs:
           uses: jaxxstorm/action-install-gh-release@v2.1.0
           with:   
             repo: aspect-build/aspect-cli
-            tag: 2025.40-21-g705e63e
+            tag: 2025.42.9
             asset-name: aspect-cli
             platform: unknown_linux
             arch: x86_64

README.md

@@ -4,3 +4,8 @@ Replacement for the 'bazel coverage' command:
 - forget having a Bazel-specific, Java-based, unmaintained LCOV merger and 'combined report' - that never should have been Bazel's job
 - developers really need git-aware diff to show "incremental coverage" - which of the lines I added or modified are covered by tests?
 - ability to add other enforcement thresholds
+- clean up the coverage .dat files in the output tree after reporting
+
+## Demo
+
+[![asciicast](https://asciinema.org/a/pQCJWxWxONi01bBZcdRgLxEHx.svg)](https://asciinema.org/a/pQCJWxWxONi01bBZcdRgLxEHx)

coverage.axl

@@ -4,36 +4,53 @@ Implement a 'coverage' task that wraps a test command.
 Gathers the coverage.dat files to power common developer workflows.
 """
 
+load("./runnable.axl", "runnable")
+
 # buildifier: disable=function-docstring
 def impl(ctx) -> int:
     out = ctx.std.io.stdout
     err = ctx.std.io.stderr
-    build = ctx.bazel.build(
+
+    lcov_build = ctx.bazel.build(
+        "@lcov",
+        events = True,
+        bazel_flags = ["--build_runfile_links"],
+    )
+    
+    lcov = runnable(ctx)
+    for event in lcov_build.events():
+        lcov.event(event)
+
+    test = ctx.bazel.build(
         "//...",
         events = True,
         bazel_flags = [
             "--isatty=" + str(int(out.is_tty)),
             "--collect_code_coverage",
         ],
         bazel_verb = "test"
-    );
+    )
 
     coverage_dat_files = []
-    for event in build.events():
+    for event in test.events():
         if event.kind == "test_result":
-            coverage_dat_files.extend([f.file.removeprefix("file://") for f in event.payload.test_action_output if f.file.endswith("coverage.dat")])
+            coverage_dat_files.extend([
+                f.file.removeprefix("file://")
+                for f in event.payload.test_action_output
+                if f.file.endswith("coverage.dat")
+            ])
         # TODO: populate a GITHUB_OUTPUT variable so we can use https://github.com/codecov/codecov-action
         if event.kind == "progress":
             out.write(event.payload.stdout)
             err.write(event.payload.stderr)
-
-        if event.kind == "build_finished_id":
-            for file in coverage_dat_files:
-                out.write(file + "\n")
-                out.write(ctx.std.fs.read_to_string(file) + "\n")
 
-    build.wait()
+    test.wait()
+
     # TODO: get the delta of changed files from VCS, and render 'incremental' coverage as the default presentation
+    exit = lcov.spawn(ctx, ["--list"] + coverage_dat_files).wait()
+
+    if not exit.success:
+        err.write("\x1b[0;31mERROR\x1b[0m: process exited with code %d\n" % exit.code)
 
     # Async: Cleanup disk space consumed by the .dat files.
     ctx.std.process.command("rm").arg("-f").args(coverage_dat_files).spawn()

example/.aspect/runnable.axl

@@ -0,0 +1 @@
+../../runnable.axl

example/MODULE.bazel

@@ -1,5 +1,6 @@
 bazel_dep(name = "aspect_rules_py", version = "1.6.3")
 bazel_dep(name = "rules_python", version = "1.6.3")
+bazel_dep(name = "lcov", version = "2.3.2")
 
 python = use_extension("@rules_python//python/extensions:python.bzl", "python")
 python.toolchain(

example/MODULE.bazel.lock

@@ -13,12 +13,8 @@ It should locate the coverage.dat files produced by the Python coverage library.
 output="$(aspect coverage //src:my_test)"
 
 # Verify that it produces the expected output - half the functions are covered
-echo "${output}" | grep -q "FNF:2" || {
-    echo >&2 "Functions Found should be 2 '${output}'"
-    exit 1
-}
-echo "${output}" | grep -q "FNH:1" || {
-    echo >&2 "Functions Hit should be 1 '${output}'"
+echo "${output}" | grep -q "50.0%" || {
+    echo >&2 "Functions should be 50% covered: '${output}'"
     exit 1
 }
 ~~~

example/README.md

@@ -0,0 +1,56 @@
+"""Copied from https://github.com/aspect-extensions/run/blob/main/runnable.axl
+TODO(alexeagle): depend on that AXL module instead
+"""
+def _process_bes(state: struct, event: bazel.build.build_event.BuildEvent):
+    filesets = state.filesets
+    target_fileset = state.target_fileset
+    target = state.target
+    if event.kind == "named_set_of_files":
+        filesets[event.id.id] = event.payload.files
+    elif event.kind == "target_completed":
+        if event.id.label == target:
+            for og in event.payload.output_group:
+                if og.name == "default":
+                    target_fileset[event.id.label] = og.file_sets
+
+def _determine_entrypoint(state: struct) -> str | None:
+    filesets = state.filesets
+    target_fileset = state.target_fileset
+    if state.target not in target_fileset:
+        return None
+    targetfs = target_fileset[state.target][0].id
+    files = filesets[targetfs]
+    entrypoint = None
+    for file in files:
+        if len(file.path_prefix):
+            entrypoint = file.file.removeprefix("file://")
+            break
+    return entrypoint
+
+def _spawn(ctx: task_context, state: struct, args: list[str]) -> std.process.child:
+    entrypoint = _determine_entrypoint(state)
+    runfiles = entrypoint + ".runfiles"
+    return ctx.std.process.command(entrypoint)\
+        .current_dir(runfiles) \
+        .env("RUNFILES_DIR", runfiles) \
+        .env("JAVA_RUNFILES", runfiles) \
+        .env("RUNFILES_MANIFEST_FILE", runfiles + "_manifest") \
+        .env("BUILD_WORKSPACE_DIRECTORY", "TODO") \
+        .env("BUILD_WORKING_DIRECTORY", ctx.std.env.current_dir()) \
+        .args(args) \
+        .spawn()
+
+def runnable(ctx) -> struct:
+    state = struct(
+        ctx = ctx,
+        target = "@@lcov+//:lcov", # TODO(alexeagle): we can assume there's only one target
+        filesets = {},
+        target_fileset = {}
+    )
+
+    return struct(
+        event = lambda event: _process_bes(state, event),
+        spawn = lambda ctx, args: _spawn(ctx, state, args),
+    )
+
+spawn = _spawn