[cli] Add config-hash command (#15548)

Co-authored-by: J. Nick Koston <nick@koston.org>
Co-authored-by: J. Nick Koston <nick@home-assistant.io>

esphome/__main__.py

@@ -1415,6 +1415,15 @@ def command_config(args: ArgsProtocol, config: ConfigType) -> int | None:
     return 0
 
 
+def command_config_hash(args: ArgsProtocol, config: ConfigType) -> int | None:
+    # generating code might modify config, so it must be done in order to generate
+    # a hash that will match what was generated when compiling and then running
+    # on the device
+    generate_cpp_contents(config)
+    safe_print(f"0x{CORE.config_hash:08x}")
+    return 0
+
+
 def command_vscode(args: ArgsProtocol) -> int | None:
     from esphome import vscode
 
@@ -1950,6 +1959,7 @@ PRE_CONFIG_ACTIONS = {
 
 POST_CONFIG_ACTIONS = {
     "config": command_config,
+    "config-hash": command_config_hash,
     "compile": command_compile,
     "upload": command_upload,
     "logs": command_logs,
@@ -2063,6 +2073,13 @@ def parse_args(argv):
         "--show-secrets", help="Show secrets in output.", action="store_true"
     )
 
+    parser_config_hash = subparsers.add_parser(
+        "config-hash", help="Calculate the hash of the configuration."
+    )
+    parser_config_hash.add_argument(
+        "configuration", help="Your YAML configuration file(s).", nargs="+"
+    )
+
     parser_compile = subparsers.add_parser(
         "compile", help="Read the configuration and compile a program."
     )

tests/unit_tests/test_main.py

@@ -29,6 +29,7 @@ from esphome.__main__ import (
     command_analyze_memory,
     command_bundle,
     command_clean_all,
+    command_config_hash,
     command_rename,
     command_run,
     command_update_all,
@@ -3439,6 +3440,33 @@ def test_command_wizard(tmp_path: Path) -> None:
         mock_wizard.assert_called_once_with(config_file)
 
 
+def test_command_config_hash(
+    tmp_path: Path,
+    capfd: CaptureFixture[str],
+) -> None:
+    """command_config_hash runs codegen then prints CORE.config_hash.
+
+    The printed format must match `0x{config_hash:08x}` used by
+    generate_build_info_data_cpp so the value can be compared byte-for-byte
+    against the ESPHOME_CONFIG_HASH embedded in firmware.
+    """
+    setup_core(tmp_path=tmp_path, config={"esphome": {"name": "test"}})
+    args = MockArgs()
+
+    # generate_cpp_contents requires real components to be loaded; mock it out
+    # so this test isolates the command's output contract. The command must
+    # still call it (codegen can mutate config, which affects the hash).
+    with patch("esphome.__main__.generate_cpp_contents") as mock_generate:
+        result = command_config_hash(args, CORE.config)
+
+    assert result == 0
+    mock_generate.assert_called_once_with(CORE.config)
+
+    output = strip_ansi_codes(capfd.readouterr().out).strip()
+    assert re.fullmatch(r"0x[0-9a-f]{8}", output)
+    assert output == f"0x{CORE.config_hash:08x}"
+
+
 def test_command_rename_invalid_characters(
     tmp_path: Path, capfd: CaptureFixture[str]
 ) -> None: