builder: include test sources in compiledb via __test target

platformio/builder/main.py

@@ -205,7 +205,15 @@
 )
 
 AlwaysBuild(env.Alias("__debug", DEFAULT_TARGETS))
-AlwaysBuild(env.Alias("__test", DEFAULT_TARGETS))
+if "compiledb" in COMMAND_LINE_TARGETS:
+    # `pio run -t compiledb -t __test` (issue #4934): "__test" is passed only
+    # to include test sources in the compilation database. Don't alias it to
+    # the default build targets — a full build would try to link every test
+    # suite (each with its own `main()`) into one program and fail, while
+    # compiledb generation itself never compiles or links anything.
+    env.Alias("__test", [])
+else:
+    AlwaysBuild(env.Alias("__test", DEFAULT_TARGETS))
 
 env.ProcessDelayedActions()
 

platformio/builder/tools/piotest.py

@@ -14,6 +14,8 @@
 
 import os
 
+from SCons.Script import COMMAND_LINE_TARGETS  # pylint: disable=import-error
+
 from platformio.builder.tools import piobuild
 from platformio.test.result import TestSuite
 from platformio.test.runners.factory import TestRunnerFactory
@@ -26,6 +28,23 @@ def ConfigureTestTarget(env):
     )
     env.Prepend(CPPPATH=["$PROJECT_TEST_DIR"])
 
+    if "PIOTEST_RUNNING_NAME" not in env and "compiledb" in COMMAND_LINE_TARGETS:
+        # A compilation database is being generated without a specific test
+        # suite selected (`pio run -t compiledb -t __test`, issue #4934).
+        # The default filter above only matches sources directly in the test
+        # dir, so nested `test_*/` suites — the documented layout — would
+        # produce "Nothing to build". Include every test suite recursively:
+        # unlike a real test build, compiledb never links, so the multiple
+        # `main()` definitions across suites are not a problem.
+        env.Append(PIOTEST_SRC_FILTER=[f"+<test_*{os.path.sep}>"])
+        test_dir = env.subst("$PROJECT_TEST_DIR")
+        if os.path.isdir(test_dir):
+            for item in sorted(os.listdir(test_dir)):
+                if item.startswith("test_") and os.path.isdir(
+                    os.path.join(test_dir, item)
+                ):
+                    env.Prepend(CPPPATH=[os.path.join("$PROJECT_TEST_DIR", item)])
+
     if "PIOTEST_RUNNING_NAME" in env:
         test_name = env["PIOTEST_RUNNING_NAME"]
         while True:

tests/commands/test_run_compiledb.py

@@ -0,0 +1,82 @@
+# Copyright (c) 2014-present PlatformIO <contact@platformio.org>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import json
+
+from platformio.run.cli import cli as cmd_run
+
+
+def _make_project_with_tests(tmpdir, extra_ini=""):
+    tmpdir.join("platformio.ini").write("""
+[env:native]
+platform = native
+%s
+""" % extra_ini)
+    tmpdir.mkdir("src").join("calc.c").write("""
+int add(int a, int b) { return a + b; }
+""")
+    tmpdir.mkdir("test").mkdir("test_calc").join("test_add.c").write("""
+int add(int a, int b);
+int main(void) { return add(1, 2) == 3 ? 0 : 1; }
+""")
+
+
+def _compiledb_files(tmpdir):
+    with open(str(tmpdir.join("compile_commands.json")), encoding="utf8") as fp:
+        return [entry["file"] for entry in json.load(fp)]
+
+
+def test_compiledb_includes_test_sources(clirunner, validate_cliresult, tmpdir):
+    # Regression test for https://github.com/platformio/platformio-core/issues/4934
+    # `pio run -t compiledb -t __test` used to fail with "Nothing to build"
+    # for the documented `test/test_*/` layout, leaving test sources (and
+    # test-framework headers like unity.h) out of the compilation database.
+    _make_project_with_tests(tmpdir)
+    result = clirunner.invoke(
+        cmd_run,
+        ["--project-dir", str(tmpdir), "-t", "compiledb", "-t", "__test"],
+    )
+    validate_cliresult(result)
+
+    files = _compiledb_files(tmpdir)
+    assert any(f.endswith("test_add.c") for f in files), files
+
+
+def test_compiledb_with_tests_and_src(clirunner, validate_cliresult, tmpdir):
+    # With `test_build_src = yes`, both the test suites and the production
+    # sources should land in the compilation database.
+    _make_project_with_tests(tmpdir, extra_ini="test_build_src = yes")
+    result = clirunner.invoke(
+        cmd_run,
+        ["--project-dir", str(tmpdir), "-t", "compiledb", "-t", "__test"],
+    )
+    validate_cliresult(result)
+
+    files = _compiledb_files(tmpdir)
+    assert any(f.endswith("test_add.c") for f in files), files
+    assert any(f.endswith("calc.c") for f in files), files
+
+
+def test_compiledb_without_test_target_unchanged(clirunner, validate_cliresult, tmpdir):
+    # Non-regression: a plain `pio run -t compiledb` must keep its current
+    # behavior — production sources only, no test sources.
+    _make_project_with_tests(tmpdir)
+    result = clirunner.invoke(
+        cmd_run, ["--project-dir", str(tmpdir), "-t", "compiledb"]
+    )
+    validate_cliresult(result)
+
+    files = _compiledb_files(tmpdir)
+    assert any(f.endswith("calc.c") for f in files), files
+    assert not any(f.endswith("test_add.c") for f in files), files