fix(cli): IDEs with plugins using BSP can now use aspect cli instead of vanilla bazel

.aspect/config.axl

@@ -362,7 +362,8 @@ def config(ctx: ConfigContext):
     # Run with: aspect dev test-bazel-flags
     ctx.tasks.add(bazel_flags_tests)
 
-    # bazel_runner.axl dispatch helpers: the bazel_attempt_end/build_end seam.
+    # bazel_runner.axl: the bazel_attempt_end/build_end dispatch seam, plus
+    # target_patterns (when the `targets` default is suppressed).
     # Run with: aspect dev test-bazel-runner
     ctx.tasks.add(bazel_runner_tests)
 

.buildkite/pipeline.yaml

@@ -329,7 +329,12 @@ steps:
       aspect test --task:name test-bk
   # Smoke-tests the new test-task flags. `--target-pattern-file` is forwarded
   # to Bazel verbatim, so the assertion is just that aspect resolves the file
-  # and the run completes. `--coverage` is exercised against an sh_test rather
+  # and the run completes. The IDE/BSP step re-runs the same pattern file in the
+  # shape the IntelliJ Bazel plugin produces through the tools/bazel wrapper —
+  # Bazel's own flag spellings behind `--bazel-flag` — and asserts the caller's
+  # BEP file is actually written. The CLI appends its own
+  # `--build_event_binary_file` last, and the Bazel option is single-valued.
+  # `--coverage` is exercised against an sh_test rather
   # than a rust_test: `toolchains_llvm_bootstrapped` 0.5.2 (pinned in
   # MODULE.bazel) ships without `libclang_rt.profile.a`, so any rust_test under
   # --collect_code_coverage fails CppLink on libld/libc shared libs (upstream
@@ -356,7 +361,16 @@ steps:
       echo "# smoke: targets forwarded via --target_pattern_file" > $$PATTERNS
       echo "//examples/test_states:always_pass" >> $$PATTERNS
       aspect test --task:name test-bk-target-pattern-file --target-pattern-file=$$PATTERNS
-      rm -f $$PATTERNS
+
+      echo "--- :aspect: IDE/BSP shape — forwarded --target_pattern_file + --build_event_binary_file"
+      BEP=$$(mktemp)
+      aspect build --task:name test-bk-ide-passthrough \
+        --bazel-flag=--target_pattern_file=$$PATTERNS \
+        --bazel-flag=--build_event_binary_file=$$BEP \
+        --bazel-flag=--build_event_binary_file_upload_mode=wait_for_upload_complete \
+        --bazel-flag=--tool_tag=bazelbsp:3.2.0
+      test -s $$BEP || { echo "caller's --build_event_binary_file was not written"; exit 1; }
+      rm -f $$BEP $$PATTERNS
 
       echo "--- :aspect: aspect test --coverage (+ --coverage-report + --coverage-tool)"
       REPORT=$$(mktemp)

.github/workflows/ci-workflows.yaml

@@ -613,7 +613,12 @@ jobs:
   # Smoke-tests the new test-task flags. Ported from the Buildkite
   # `test-flags-task` step. `--target-pattern-file` is forwarded to Bazel
   # verbatim, so the assertion is just that aspect resolves the file and the run
-  # completes. `--coverage` is exercised against an sh_test rather than a
+  # completes. The IDE/BSP step re-runs the same pattern file in the shape the
+  # IntelliJ Bazel plugin produces through the tools/bazel wrapper — Bazel's own
+  # flag spellings behind `--bazel-flag` — and asserts the caller's BEP file is
+  # actually written. The CLI appends its own `--build_event_binary_file` last,
+  # and the Bazel option is single-valued.
+  # `--coverage` is exercised against an sh_test rather than a
   # rust_test: toolchains_llvm_bootstrapped 0.5.2 (pinned in MODULE.bazel) ships
   # without libclang_rt.profile.a, so any rust_test under --collect_code_coverage
   # fails CppLink (upstream hermeticbuild/hermetic-llvm#318, fixed in #468 — not
@@ -636,7 +641,16 @@ jobs:
           echo "# smoke: targets forwarded via --target_pattern_file" > "$PATTERNS"
           echo "//examples/test_states:always_pass" >> "$PATTERNS"
           aspect test --task:name test-gha-target-pattern-file --target-pattern-file="$PATTERNS"
-          rm -f "$PATTERNS"
+
+          echo "--- IDE/BSP shape — forwarded --target_pattern_file + --build_event_binary_file"
+          BEP=$(mktemp)
+          aspect build --task:name test-gha-ide-passthrough \
+            --bazel-flag=--target_pattern_file="$PATTERNS" \
+            --bazel-flag=--build_event_binary_file="$BEP" \
+            --bazel-flag=--build_event_binary_file_upload_mode=wait_for_upload_complete \
+            --bazel-flag=--tool_tag=bazelbsp:3.2.0
+          test -s "$BEP" || { echo "caller's --build_event_binary_file was not written"; exit 1; }
+          rm -f "$BEP" "$PATTERNS"
 
           echo "--- aspect test --coverage (+ --coverage-report + --coverage-tool)"
           REPORT=$(mktemp)

.gitignore

@@ -14,4 +14,8 @@ site
 # macOS desktop services files
 .DS_Store
 
-.claude
+.claude
+
+# IDE project state and the JetBrains Bazel plugin's generated aspect files
+.idea/
+.bazelbsp/

crates/aspect-cli/src/builtins/aspect/bazel/build_events.axl

@@ -12,6 +12,11 @@ once rather than twice. Because that can leave no sink at all — and the Aspect
 Web UI link keys on an id only a sink mints — a task pairs the collect call with
 `bes_streamed_by_bazel`, which redirects the link to Bazel's invocation id.
 
+`collect_bes_sinks` also covers the one Bazel-facing BEP flag the CLI would
+otherwise clobber: a caller's `--build_event_binary_file` becomes a CLI file sink,
+because `Build::spawn` appends the CLI's own path to that single-valued option
+last and last wins. See `collect_bes_sinks` for what that changes.
+
 The Aspect login JWT is attached to an Aspect-owned backend's sink metadata when
 the user has not supplied their own `authorization` header — see
 `aspect_endpoint_auth.axl` for the host gate and best-effort credential
@@ -55,6 +60,22 @@ def bazel_bes_backend(rc, command: str) -> str:
         return ""
     return rc.flag_value("--bes_backend", command = command) or ""
 
+def bazel_bep_file(rc, command: str) -> str:
+    """The `--build_event_binary_file` path the caller asked Bazel to write, or `""`.
+
+    Reads through the run command, so it sees the flag wherever it came from —
+    `--bazel-flag=--build_event_binary_file=…`, a `.bazelrc`, or an expanded
+    `--config`. `rc` may be `None` for a caller with no run command to consult.
+
+    Nobody but the caller sets this: the CLI's own BEP file is appended inside
+    `Build::spawn`, after rc expansion, and never passes through the rc.
+
+    Public so `build_events_test.axl` can assert the resolution.
+    """
+    if rc == None:
+        return ""
+    return rc.flag_value("--build_event_binary_file", command = command) or ""
+
 def _drop_bazel_streamed(items: list, uri_of, bazel_backend: str) -> list:
     """`items` minus those whose `uri_of(item)` names the same endpoint as Bazel's
     own `bazel_backend`.
@@ -106,16 +127,38 @@ def collect_bes_sinks(ctx, bazel_trait, rc, command: str = "build", extra_backen
     Sinks to the endpoint Bazel's own `--bes_backend` uploads to are dropped from
     both groups so the invocation is streamed once — see `_drop_bazel_streamed`.
 
+    Last comes a file sink for the caller's own `--build_event_binary_file`, when
+    they asked for one. Bazel cannot write two: the option is single-valued and
+    `Build::spawn` appends the CLI's path last, so the caller's file would
+    silently never be written. Writing it as a sink instead re-creates it from
+    Bazel's own byte stream — the file sinks share the BES reader's raw-bytes
+    path, so the result is what Bazel would have written. This is what lets IDE /
+    BSP tooling (the IntelliJ Bazel plugin) drive builds through the
+    `tools/bazel` wrapper and still get its BEP back. Two consequences worth
+    knowing: `--build_event_binary_file_upload_mode` no longer governs that file
+    (the caller's `wait()` on the returned sinks is what completes it, before the
+    task concludes), and `--build_event_json_file` / `--build_event_text_file`
+    are untouched — different flags, so Bazel still writes those itself.
+
     The one call a bazel-spawning task makes; pair it with
     `bes_streamed_by_bazel` to keep the Aspect Web UI link resolvable. The caller
     `wait()`s the returned sinks after the build.
     """
     bazel_backend = bazel_bes_backend(rc, command)
-    return (
+    sinks = (
         collect_bes_from_args(ctx, extra_backends = extra_backends, bazel_backend = bazel_backend) +
         _drop_bazel_streamed(list(bazel_trait.build_event_sinks), lambda s: s.uri, bazel_backend)
     )
 
+    # Not routed through `_drop_bazel_streamed`: a file is a local dump, not a
+    # second upload to an endpoint Bazel already streams to.
+    bep_file = bazel_bep_file(rc, command)
+    if bep_file:
+        trace.event("bes.caller_bep_file", fields = {"path": bep_file, "command": command})
+        sinks.append(bazel.build_events.file(path = bep_file))
+
+    return sinks
+
 def dropped_bes_backends(ctx, bazel_trait, rc, command: str = "build", extra_backends = []) -> list[str]:
     """The BES endpoints `collect_bes_sinks` skipped because Bazel uploads to them
     itself, deduped. Same inputs as that call — pass the same arguments.

crates/aspect-cli/src/builtins/aspect/bazel/build_events_test.axl

@@ -1,13 +1,14 @@
 """Tests for `bazel/build_events.axl` — the BES upload summary line, the gRPC-sink
 filter shared by the announce/summary helpers, sink collection, and the
 duplicate-stream drop that keeps the CLI from streaming to an endpoint Bazel's
-own `--bes_backend` already uploads to.
+own `--bes_backend` already uploads to, and the file-sink tee that keeps a
+caller's `--build_event_binary_file` from being silently clobbered.
 
 Run with:
   aspect dev test-bes-sinks
 """
 
-load("@aspect//bazel/build_events.axl", "bazel_bes_backend", "bes_results_line", "bes_streamed_by_bazel", "bes_upload_line", "collect_bes_from_args", "collect_bes_sinks", "dropped_bes_backends", "grpc_backends")
+load("@aspect//bazel/build_events.axl", "bazel_bep_file", "bazel_bes_backend", "bes_results_line", "bes_streamed_by_bazel", "bes_upload_line", "collect_bes_from_args", "collect_bes_sinks", "dropped_bes_backends", "grpc_backends")
 
 def _eq(label, got, want):
     if got != want:
@@ -248,6 +249,44 @@ def _test_collect_bes_sinks(_):
         [None, "grpcs://bes.other.example.com"],
     )
 
+def _test_bazel_bep_file(_):
+    """`bazel_bep_file` reads the caller's `--build_event_binary_file` off the run
+    command, so it sees the flag from `--bazel-flag=`, a `.bazelrc`, or a
+    `--config` expansion alike."""
+    _eq("caller asked for one", bazel_bep_file(_fake_rc({"--build_event_binary_file": "/tmp/bep.binpb"}), "build"), "/tmp/bep.binpb")
+    _eq("flag unset", bazel_bep_file(_fake_rc({}), "build"), "")
+    _eq("no run command", bazel_bep_file(None, "build"), "")
+
+def _test_collect_bes_sinks_tees_caller_bep_file(_):
+    """A caller's `--build_event_binary_file` becomes a trailing file sink, so the
+    path they asked for is written from Bazel's own byte stream.
+
+    Without it their file is silently empty: the Bazel option is single-valued and
+    `Build::spawn` appends the CLI's own path last."""
+    trait = _fake_trait([struct(uri = "grpcs://bes.other.example.com")])
+
+    def uris(rc_values):
+        ctx = _fake_ctx(bes_backends = [])
+        return [s.uri for s in collect_bes_sinks(ctx, trait, _fake_rc(rc_values))]
+
+    _eq(
+        "file sink appended after the trait's own",
+        uris({"--build_event_binary_file": "/tmp/bep.binpb"}),
+        ["grpcs://bes.other.example.com", None],
+    )
+    _eq("no BEP flag, no extra sink", uris({}), ["grpcs://bes.other.example.com"])
+
+    # The tee is a local dump, so it survives the duplicate-stream drop that
+    # suppresses a CLI sink to the endpoint Bazel itself uploads to.
+    duplicate = "grpcs://bes.acme.aspect.build"
+    ctx = _fake_ctx(bes_backends = [duplicate])
+    rc = _fake_rc({"--bes_backend": duplicate, "--build_event_binary_file": "/tmp/bep.binpb"})
+    _eq(
+        "kept while every gRPC sink is suppressed",
+        [s.uri for s in collect_bes_sinks(ctx, _fake_trait([struct(uri = duplicate)]), rc)],
+        [None],
+    )
+
 def _test_bes_streamed_by_bazel(_):
     """True only when Bazel's `--bes_backend` is the runner's own Aspect BES
     backend — the case where the Web UI still holds the invocation (under
@@ -280,6 +319,8 @@ _UNIT_TESTS = [
     _test_bazel_bes_backend,
     _test_collect_drops_duplicate_backends,
     _test_collect_bes_sinks,
+    _test_bazel_bep_file,
+    _test_collect_bes_sinks_tees_caller_bep_file,
     _test_bes_streamed_by_bazel,
 ]
 

crates/aspect-cli/src/builtins/aspect/private/lib/bazel_runner.axl

@@ -218,6 +218,38 @@ def _emit_terminal(ctx, lifecycle, command, data, exit_code, targets = []):
         flagged = final_status == "warning",
     )
 
+
+def target_patterns(explicit: bool, cli_targets: list[str], own_pattern_file: str, rc, command: str) -> list[str]:
+    """The target patterns to place on Bazel's command line.
+
+    Bazel rejects an invocation carrying both command-line patterns and
+    `--target_pattern_file` — that pair has no last-wins rule — so the single
+    decision here is whether to materialize the `targets` arg's declared
+    default (`["..."]`), a pattern the user never typed. Explicit patterns
+    always pass through: when they conflict with a pattern file, Bazel reports
+    it, and this runner does not grow a second spelling of that error.
+
+    A pattern file counts no matter which spelling delivered it: aspect's own
+    `--target-pattern-file` arrives as `own_pattern_file`, while Bazel's
+    `--target_pattern_file` reaches `rc` — from `--bazel-flag`, `.bazelrc`, or
+    a `--config` expansion alike, resolved with Bazel's own last-wins parsing.
+
+    Args:
+        explicit:         whether the user actually passed target patterns
+                          (`ctx.args.is_explicit("targets")`) rather than
+                          inheriting the arg's default.
+        cli_targets:      `ctx.args.targets` — never empty (the arg declares
+                          `default = ["..."]`, `minimum = 1`).
+        own_pattern_file: value of aspect's `--target-pattern-file`, or `""`.
+        rc:               the active `RunCommand`; only `flag_value` is used.
+        command:          Bazel subcommand whose options `rc` resolves.
+    """
+    if explicit:
+        return cli_targets
+    if own_pattern_file or rc.flag_value("--target_pattern_file", command = command):
+        return []
+    return cli_targets
+
 def run_bazel_task(ctx: TaskContext, command: str, targets = None) -> TaskConclusion:
     """Shared impl for build/test tasks.
 
@@ -258,26 +290,22 @@ def run_bazel_task(ctx: TaskContext, command: str, targets = None) -> TaskConclu
     deployment = deployment_endpoint_flags(ctx)
     base_flags.extend(deployment.base_flags)
 
-    if targets == None:
-        # --target-pattern-file is only honored when the task declares it.
-        pattern_file = getattr(ctx.args, "target_pattern_file", "") if hasattr(ctx.args, "target_pattern_file") else ""
-        if pattern_file:
-            if ctx.args.is_explicit("targets"):
-                fail("--target-pattern-file cannot be combined with command-line target patterns")
-            if not ctx.std.fs.exists(pattern_file):
-                fail("--target-pattern-file: file not found: " + pattern_file)
-            base_flags.append("--target_pattern_file=" + pattern_file)
-            targets = []
-        else:
-            targets = ctx.args.targets
+    # Patterns resolve after the rc parse below, so `setup` opens with what the
+    # user stated and the spawn refines it to the resolved list.
+    if targets != None:
+        subject = " ".join(targets)
+    elif ctx.args.is_explicit("targets"):
+        subject = " ".join(ctx.args.targets)
+    else:
+        subject = ""
 
     data = init_data()
 
     # The single pre-task `setup` phase: status-surface init + first render, rc
     # parse + `use_rc`, health checks. The active run command drives the
     # build/test below (a failed health check concludes the surface and fails
     # the task inside setup_phase).
-    rc = setup_phase(ctx, lifecycle, " ".join(targets), "bazel_results", data, hc_trait, bazel_trait, command, bazel_base_flags = base_flags)
+    rc = setup_phase(ctx, lifecycle, subject, "bazel_results", data, hc_trait, bazel_trait, command, bazel_base_flags = base_flags)
     announce_version, announce_command = resolve_bazel_announce(ctx)
 
     # Announced with the first spawn below (the streams belong to the spawn) and
@@ -299,6 +327,26 @@ def run_bazel_task(ctx: TaskContext, command: str, targets = None) -> TaskConclu
     invocation_flags = aspect_endpoint_auth_flags(ctx, rc, command)
     invocation_flags.extend(bes_results_url_flag(ctx, rc, bes_sinks, deployment, command))
 
+    if targets == None:
+        # aspect's own `--target-pattern-file` (declared by build/test only) is a
+        # per-invocation flag, not rc material — and keeping it out of the parsed
+        # rc is what lets `target_patterns` ask `rc` about the forwarded
+        # spelling. Forwarded rather than expanded into argv, since the flag
+        # exists to bypass OS command-line length limits.
+        own_pattern_file = getattr(ctx.args, "target_pattern_file", "") if hasattr(ctx.args, "target_pattern_file") else ""
+        if own_pattern_file:
+            if not ctx.std.fs.exists(own_pattern_file):
+                fail("--target-pattern-file: file not found: " + own_pattern_file)
+            invocation_flags.append("--target_pattern_file=" + own_pattern_file)
+
+        targets = target_patterns(
+            ctx.args.is_explicit("targets"),
+            ctx.args.targets,
+            own_pattern_file,
+            rc,
+            command,
+        )
+
     # The same viewer reaches the CI surfaces through `data` — they key the link on the
     # sink's own id rather than reading it off the command line. A property of the
     # resolved flags, so it is restored onto each retry's fresh `data`.
@@ -369,6 +417,10 @@ def run_bazel_task(ctx: TaskContext, command: str, targets = None) -> TaskConclu
                 # work, just attempted again.
                 emoji = "🧪" if command == "test" else "🔨",
             ),
+            # The resolved patterns are only known after the rc parse, so the
+            # `setup` surface opened without them; name them here. A pattern-file
+            # run resolves to no patterns, and `""` means "no change".
+            subject = " ".join(targets),
         )
 
         # Disclose what this bazel call was wired with, after the spawn phase