Create and use buildinfo.json instead of parsing linker script

Co-authored-by: J. Nick Koston <nick+github@koston.org>

esphome/__main__.py

@@ -528,44 +528,37 @@ def compile_program(args: ArgsProtocol, config: ConfigType) -> int:
 
 def _check_and_emit_buildinfo():
     """Check if firmware was rebuilt and emit buildinfo."""
+    import json
 
     firmware_path = CORE.firmware_bin
-    buildinfo_ld_path = CORE.relative_build_path("buildinfo.ld")
+    buildinfo_json_path = CORE.relative_build_path("buildinfo.json")
 
     # Check if both files exist
-    if not firmware_path.exists() or not buildinfo_ld_path.exists():
+    if not firmware_path.exists() or not buildinfo_json_path.exists():
         return
 
-    # Check if firmware is newer than buildinfo linker script (indicating a relink occurred)
-    if firmware_path.stat().st_mtime <= buildinfo_ld_path.stat().st_mtime:
+    # Check if firmware is newer than buildinfo (indicating a relink occurred)
+    if firmware_path.stat().st_mtime <= buildinfo_json_path.stat().st_mtime:
         return
 
-    # Read buildinfo values from linker script
+    # Read buildinfo from JSON
     try:
-        with open(buildinfo_ld_path, encoding="utf-8") as f:
-            content = f.read()
-    except OSError as e:
+        with open(buildinfo_json_path, encoding="utf-8") as f:
+            buildinfo = json.load(f)
+    except (OSError, json.JSONDecodeError) as e:
         _LOGGER.debug("Failed to read buildinfo: %s", e)
         return
 
-    config_hash_match = re.search(r"ESPHOME_CONFIG_HASH = 0x([0-9a-fA-F]+);", content)
-    build_time_match = re.search(r"ESPHOME_BUILD_TIME = (\d+);", content)
+    config_hash = buildinfo.get("config_hash")
+    build_time = buildinfo.get("build_time")
 
-    if not config_hash_match or not build_time_match:
+    if config_hash is None or build_time is None:
         return
 
-    config_hash = config_hash_match.group(1)
-    build_time = int(build_time_match.group(1))
-
     # Emit buildinfo
-    print("=== ESPHome Build Info ===")
-    print(f"Config Hash: 0x{config_hash}")
-    print(
-        f"Build Time:  {build_time} ({time.strftime('%Y-%m-%d %H:%M:%S %z', time.localtime(build_time))})"
+    _LOGGER.info(
+        "Build Info: config_hash=0x%08x build_time=%s", config_hash, build_time
     )
-    print("===========================")
-
-    # TODO: Future commit will create JSON manifest with OTA metadata here
 
 
 def upload_using_esptool(

esphome/writer.py

@@ -1,5 +1,6 @@
 from collections.abc import Callable
 import importlib
+import json
 import logging
 import os
 from pathlib import Path
@@ -249,8 +250,16 @@ def copy_src_tree():
     write_file_if_changed(
         CORE.relative_src_path("esphome", "core", "version.h"), generate_version_h()
     )
-    # Write buildinfo linker script and copy the PlatformIO script
-    write_file(CORE.relative_build_path("buildinfo.ld"), generate_buildinfo_ld())
+    # Write buildinfo linker script, JSON metadata, and copy the PlatformIO script
+    config_hash, build_time, build_time_str = get_buildinfo()
+    write_file(
+        CORE.relative_build_path("buildinfo.ld"),
+        generate_buildinfo_ld(config_hash, build_time, build_time_str),
+    )
+    write_file(
+        CORE.relative_build_path("buildinfo.json"),
+        json.dumps({"config_hash": config_hash, "build_time": build_time}),
+    )
     copy_file_if_changed(
         Path(__file__).parent / "core" / "buildinfo.py.script",
         CORE.relative_build_path("buildinfo.py"),
@@ -306,17 +315,27 @@ def _encode_string_symbols(
     return symbols
 
 
-def generate_buildinfo_ld() -> str:
-    """Generate buildinfo linker script with config hash and build time."""
+def get_buildinfo() -> tuple[int, int, str]:
+    """Calculate buildinfo values from current config.
+
+    Returns:
+        Tuple of (config_hash, build_time, build_time_str)
+    """
     from esphome import yaml_util
 
     # Use the same clean YAML representation as 'esphome config' command
     config_str = yaml_util.dump(CORE.config, show_secrets=True)
     config_hash = fnv1a_32bit_hash(config_str)
-    config_hash_str = f"{config_hash:08x}"
-
     build_time = int(time.time())
     build_time_str = time.strftime("%b %d %Y, %H:%M:%S", time.localtime(build_time))
+    return config_hash, build_time, build_time_str
+
+
+def generate_buildinfo_ld(
+    config_hash: int, build_time: int, build_time_str: str
+) -> str:
+    """Generate buildinfo linker script with config hash and build time."""
+    config_hash_str = f"{config_hash:08x}"
 
     # Generate symbols for all 4 variants: 32LE, 32BE, 64LE, 64BE
     all_variants: list[str] = []