Warn when a compile entry does not lead with a compiler and fail on an empty core archive

tests/unit_tests/build_gen/test_arduino8266.py

@@ -646,3 +646,22 @@ def test_shell_token_escaping() -> None:
     assert arduino8266._shell_token('-DX=a\\"b c') == '"-DX=a\\\\\\"b c"'
     # A trailing backslash run doubles before the closing quote
     assert arduino8266._shell_token("a b\\") == '"a b\\\\"'
+
+
+def test_write_project_empty_core_raises(tmp_path: Path) -> None:
+    """A framework tree with no core sources fails at generation, not link."""
+    paths = _make_framework(tmp_path)
+    core = paths["framework_path"] / "cores" / "esp8266"
+    for f in core.iterdir():
+        f.unlink()
+    _set_flags()
+    src = CORE.relative_src_path()
+    (src / "esphome" / "components" / "esp8266").mkdir(parents=True, exist_ok=True)
+    (src / "main.cpp").write_text("")
+    with (
+        patch.object(arduino8266, "generate_ld_scripts"),
+        patch("esphome.arduino8266.component.resolve_libraries", return_value=[]),
+        patch("esphome.arduino8266.framework.ccache_path", return_value=None),
+        pytest.raises(EsphomeError, match="no core sources"),
+    ):
+        arduino8266.write_project(paths)

tests/unit_tests/test_espidf_idedata.py

@@ -279,11 +279,26 @@ def test_parse_entry_strips_launcher_prefix() -> None:
     assert cxx_path == "/tools/xtensa-lx106-elf-g++"
     assert defines == ["USE_ESP8266"]
     # Without a configured launcher nothing is stripped, even a token that
-    # happens to be named ccache
+    # happens to be named ccache -- but the surprise is warned about
     cxx_path, _, _, _ = idedata._parse_entry(entry)
     assert cxx_path == "/opt/homebrew/bin/ccache"
 
 
+def test_parse_entry_warns_when_first_token_is_not_a_compiler(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    entry = _entry(
+        f"{ABS}build",
+        f"{ABS}build/src/esphome/core/application.cpp",
+        "/opt/homebrew/bin/ccache /tools/xtensa-lx106-elf-g++ -c a.cpp -o a.o",
+    )
+    idedata._parse_entry(entry)
+    assert "does not start with a compiler" in caplog.text
+    caplog.clear()
+    idedata._parse_entry(entry, launcher="/opt/homebrew/bin/ccache")
+    assert "does not start with a compiler" not in caplog.text
+
+
 def _write_compile_commands(tmp_path: Path) -> Path:
     compile_commands = tmp_path / "compile_commands.json"
     compile_commands.write_text(