Drop the app archive from ldgen_libraries too and add a fragment check

esphome/espidf/framework.py

@@ -686,21 +686,24 @@ def _patch_tools_json_demote_unused_tools(framework_path: Path) -> None:
     )
 
 
-_LDGEN_COMMAND_ANCHOR = "    add_custom_command(\n"
+_LDGEN_JOIN_ANCHOR = '    list(JOIN ldgen_libraries_expr "\\n" ldgen_libraries_str)\n'
 _LDGEN_DEP_FILTER = """\
-    # Patched by ESPHome: drop app-only archives from ldgen DEPENDS.
+    # Patched by ESPHome: drop app-only archives from ldgen's inputs.
     # ldgen only reads archives named in mapping fragments' archive: lines;
-    # the app component never appears there, so rebuilding it cannot change
-    # the generated linker script. Set by the ESPHome project CMakeLists.
+    # the app component never appears there, so it cannot change the output,
+    # and keeping it listed would race ldgen's objdump against the archive
+    # being written. Set by the ESPHome project CMakeLists.
     if(ESPHOME_LDGEN_DEP_EXCLUDE)
         list(REMOVE_ITEM ldgen_deps ${ESPHOME_LDGEN_DEP_EXCLUDE})
+        foreach(esphome_ldgen_excl ${ESPHOME_LDGEN_DEP_EXCLUDE})
+            list(REMOVE_ITEM ldgen_libraries_expr "$<TARGET_FILE:${esphome_ldgen_excl}>")
+        endforeach()
     endif()
-    add_custom_command(
 """
 
 
 def _patch_ldgen_cmake(framework_path: Path) -> None:
-    """Let projects drop their app archive from the sections.ld DEPENDS.
+    """Let projects drop their app archive from ldgen's inputs.
 
     Guarded by ESPHOME_LDGEN_DEP_EXCLUDE, which only the ESPHome project
     CMakeLists sets, so stock IDF builds using the shared framework copy
@@ -720,7 +723,7 @@ def _patch_ldgen_cmake(framework_path: Path) -> None:
         return
     if "ESPHOME_LDGEN_DEP_EXCLUDE" in content:
         return
-    if "${ldgen_deps}" not in content or content.count(_LDGEN_COMMAND_ANCHOR) != 1:
+    if "${ldgen_deps}" not in content or content.count(_LDGEN_JOIN_ANCHOR) != 1:
         _LOGGER.warning(
             "ldgen.cmake at %s does not match the expected layout; "
             "skipping the ldgen dependency patch (builds stay correct).",
@@ -728,7 +731,8 @@ def _patch_ldgen_cmake(framework_path: Path) -> None:
         )
         return
     write_file_if_changed(
-        ldgen_cmake, content.replace(_LDGEN_COMMAND_ANCHOR, _LDGEN_DEP_FILTER)
+        ldgen_cmake,
+        content.replace(_LDGEN_JOIN_ANCHOR, _LDGEN_DEP_FILTER + _LDGEN_JOIN_ANCHOR),
     )
     _LOGGER.info("Patched %s to honor ESPHOME_LDGEN_DEP_EXCLUDE.", ldgen_cmake)
 

esphome/espidf/toolchain.py

@@ -24,7 +24,7 @@ from esphome.core import CORE, EsphomeError
 from esphome.espidf import variant_to_idf_target
 from esphome.espidf.framework import check_esp_idf_install, get_framework_env
 from esphome.espidf.size_summary import print_summary
-from esphome.helpers import add_git_ceiling_directory, write_file
+from esphome.helpers import add_git_ceiling_directory, get_bool_env, write_file
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -479,6 +479,36 @@ def _patch_memory_segments():
         _LOGGER.warning("Could not patch memory segments in %s", memory_ld)
 
 
+_LDGEN_FRAGMENTS_RE = re.compile(r'--fragments-list\s+"([^"]+)"')
+_APP_ARCHIVE_MAPPED_RE = re.compile(r"^archive:\s*libsrc\.a\s*$", re.MULTILINE)
+
+
+def _warn_if_app_archive_mapped() -> None:
+    """Belt for the ldgen dependency exclusion (see build_gen/espidf.py).
+
+    The exclusion is safe only while no linker fragment names the app
+    archive; if one ever did, ldgen would silently skip remapping it, so
+    surface that loudly instead of relying on the invariant forever.
+    """
+    build_ninja = CORE.relative_build_path("build", "build.ninja")
+    try:
+        match = _LDGEN_FRAGMENTS_RE.search(build_ninja.read_text(encoding="utf-8"))
+        if match is None:
+            return
+        for fragment in match.group(1).split(";"):
+            if _APP_ARCHIVE_MAPPED_RE.search(
+                Path(fragment).read_text(encoding="utf-8")
+            ):
+                _LOGGER.warning(
+                    "Linker fragment %s maps the app archive; its entries may be "
+                    "skipped. Set ESPHOME_LDGEN_FULL_DEPS=1 and rebuild.",
+                    fragment,
+                )
+                return
+    except OSError as e:
+        _LOGGER.debug("Skipping ldgen fragment check: %s", e)
+
+
 def run_compile(config, verbose: bool) -> int:
     """Compile the ESP-IDF project.
 
@@ -505,6 +535,9 @@ def run_compile(config, verbose: bool) -> int:
             if path.is_file():
                 os.utime(path)
 
+    if not get_bool_env("ESPHOME_LDGEN_FULL_DEPS"):
+        _warn_if_app_archive_mapped()
+
     # In testing mode, generate the linker script first, patch DRAM/IRAM sizes,
     # then build. memory.ld is regenerated by ninja during the build phase,
     # so we must patch after it's generated but before linking (same timing

tests/unit_tests/test_espidf_framework.py

@@ -876,6 +876,9 @@ _LDGEN_CMAKE_STOCK = """\
 function(__ldgen_create_target exe_target)
     idf_build_get_property(python PYTHON)
 
+    list(JOIN ldgen_libraries_expr "\\n" ldgen_libraries_str)
+    file(WRITE ${build_dir}/ldgen_libraries.in "${ldgen_libraries_str}")
+
     add_custom_command(
         OUTPUT ${output}
         COMMAND ${python} "${idf_path}/tools/ldgen/ldgen.py"
@@ -899,6 +902,10 @@ def test_patch_ldgen_cmake_inserts_guarded_filter(tmp_path: Path) -> None:
     _patch_ldgen_cmake(tmp_path)
     content = ldgen_cmake.read_text(encoding="utf-8")
     assert _LDGEN_DEP_FILTER in content
+    # The libraries list must be filtered before it is serialized to disk
+    assert content.index("REMOVE_ITEM ldgen_libraries_expr") < content.index(
+        "list(JOIN ldgen_libraries_expr"
+    )
     assert "DEPENDS     ${template}" in content
 
 
@@ -931,8 +938,9 @@ def test_patch_ldgen_cmake_unreadable_file_warns_and_skips(
             id="no_ldgen_deps",
         ),
         pytest.param(
-            _LDGEN_CMAKE_STOCK + "\n    add_custom_command(\n        OUTPUT x)\n",
-            id="duplicate_command",
+            _LDGEN_CMAKE_STOCK
+            + '\n    list(JOIN ldgen_libraries_expr "\\n" ldgen_libraries_str)\n',
+            id="duplicate_join",
         ),
     ],
 )

tests/unit_tests/test_espidf_toolchain.py

@@ -623,6 +623,45 @@ def test_component_cache_ignores_corrupt_file(setup_core: Path, tmp_path: Path)
         assert toolchain.load_cached_builtin_components() is None
 
 
+def _write_fragments_build_ninja(tmp_path: Path, fragments: list[Path]) -> None:
+    build_dir = CORE.relative_build_path("build")
+    build_dir.mkdir(parents=True, exist_ok=True)
+    frag_list = ";".join(str(f) for f in fragments)
+    (build_dir / "build.ninja").write_text(
+        f'  COMMAND = python ldgen.py --fragments-list "{frag_list}" --input x\n'
+    )
+
+
+def test_warn_if_app_archive_mapped_warns(
+    setup_core: Path, tmp_path: Path, caplog: pytest.LogCaptureFixture
+) -> None:
+    """A fragment naming the app archive triggers the loud warning."""
+    _setup_build(setup_core)
+    frag = tmp_path / "linker.lf"
+    frag.write_text("[mapping:evil]\narchive: libsrc.a\nentries:\n    * (noflash)\n")
+    _write_fragments_build_ninja(tmp_path, [frag])
+    toolchain._warn_if_app_archive_mapped()
+    assert "maps the app archive" in caplog.text
+
+
+def test_warn_if_app_archive_mapped_clean(
+    setup_core: Path, tmp_path: Path, caplog: pytest.LogCaptureFixture
+) -> None:
+    """Normal fragments produce no warning; missing files are non-fatal."""
+    _setup_build(setup_core)
+    frag = tmp_path / "linker.lf"
+    frag.write_text("[mapping:freertos]\narchive: libfreertos.a\n")
+    _write_fragments_build_ninja(tmp_path, [frag, tmp_path / "missing.lf"])
+    toolchain._warn_if_app_archive_mapped()
+    assert "maps the app archive" not in caplog.text
+
+
+def test_warn_if_app_archive_mapped_no_build_ninja(setup_core: Path) -> None:
+    """No build.ninja yet is a quiet no-op."""
+    _setup_build(setup_core)
+    toolchain._warn_if_app_archive_mapped()
+
+
 def test_run_compile_passes_compile_process_limit(setup_core: Path) -> None:
     """compile_process_limit is forwarded to run_idf_py as the job limit."""
     _setup_build(setup_core)