fix(config): do not write env vars to config files

Add class `DefaultInvokeAIAppConfig`, which inherits from `InvokeAIAppConfig`. When instantiated, this class does not parse environment variables, so it outputs a "clean" default config. That's the only difference.

Then, we can use this new class in the 3 places:
- When creating the example config file (no env vars should be here)
- When migrating a v3 config (we want to instantiate the migrated config without env vars, so that when we write it out, they are not written to disk)
- When creating a fresh config file (i.e. on first run with an uninitialized root or new config file path - no env vars here!)

invokeai/app/services/config/config_default.py

@@ -13,7 +13,7 @@ from typing import Any, Literal, Optional
 import psutil
 import yaml
 from pydantic import BaseModel, Field, PrivateAttr, field_validator
-from pydantic_settings import BaseSettings, SettingsConfigDict
+from pydantic_settings import BaseSettings, PydanticBaseSettingsSource, SettingsConfigDict
 
 import invokeai.configs as model_configs
 from invokeai.backend.model_hash.model_hash import HASHING_ALGORITHMS
@@ -332,6 +332,27 @@ class InvokeAIAppConfig(BaseSettings):
         return root
 
 
+class DefaultInvokeAIAppConfig(InvokeAIAppConfig):
+    """A version of `InvokeAIAppConfig` that does not automatically parse any settings from environment variables
+    or any file.
+
+    This is useful for writing out a default config file.
+
+    Note that init settings are set if provided.
+    """
+
+    @classmethod
+    def settings_customise_sources(
+        cls,
+        settings_cls: type[BaseSettings],
+        init_settings: PydanticBaseSettingsSource,
+        env_settings: PydanticBaseSettingsSource,
+        dotenv_settings: PydanticBaseSettingsSource,
+        file_secret_settings: PydanticBaseSettingsSource,
+    ) -> tuple[PydanticBaseSettingsSource, ...]:
+        return (init_settings,)
+
+
 def migrate_v3_config_dict(config_dict: dict[str, Any]) -> InvokeAIAppConfig:
     """Migrate a v3 config dictionary to a current config object.
 
@@ -367,7 +388,8 @@ def migrate_v3_config_dict(config_dict: dict[str, Any]) -> InvokeAIAppConfig:
             elif k in InvokeAIAppConfig.model_fields:
                 # skip unknown fields
                 parsed_config_dict[k] = v
-    config = InvokeAIAppConfig.model_validate(parsed_config_dict)
+    # When migrating the config file, we should not include currently-set environment variables.
+    config = DefaultInvokeAIAppConfig.model_validate(parsed_config_dict)
 
     return config
 
@@ -391,14 +413,13 @@ def load_and_migrate_config(config_path: Path) -> InvokeAIAppConfig:
         # This is a v3 config file, attempt to migrate it
         shutil.copy(config_path, config_path.with_suffix(".yaml.bak"))
         try:
-            # This could be the wrong shape, but we will catch all exceptions below
-            config = migrate_v3_config_dict(loaded_config_dict)  # pyright: ignore [reportUnknownArgumentType]
+            # loaded_config_dict could be the wrong shape, but we will catch all exceptions below
+            migrated_config = migrate_v3_config_dict(loaded_config_dict)  # pyright: ignore [reportUnknownArgumentType]
         except Exception as e:
             shutil.copy(config_path.with_suffix(".yaml.bak"), config_path)
             raise RuntimeError(f"Failed to load and migrate v3 config file {config_path}: {e}") from e
-        # By excluding defaults, we ensure that the new config file only contains the settings that were explicitly set
-        config.write_file(config_path)
-        return config
+        migrated_config.write_file(config_path)
+        return migrated_config
     else:
         # Attempt to load as a v4 config file
         try:
@@ -426,6 +447,7 @@ def get_config() -> InvokeAIAppConfig:
 
     On subsequent calls, the object is returned from the cache.
     """
+    # This object includes environment variables, as parsed by pydantic-settings
     config = InvokeAIAppConfig()
 
     args = InvokeAIArgs.args
@@ -441,8 +463,8 @@ def get_config() -> InvokeAIAppConfig:
     if config_file := getattr(args, "config_file", None):
         config._config_file = Path(config_file)
 
-    # Create the example file from a deep copy, with some extra values provided
-    example_config = config.model_copy(deep=True)
+    # Create the example config file, with some extra example values provided
+    example_config = DefaultInvokeAIAppConfig()
     example_config.remote_api_tokens = [
         URLRegexTokenPair(url_regex="cool-models.com", token="my_secret_token"),
         URLRegexTokenPair(url_regex="nifty-models.com", token="some_other_token"),
@@ -454,10 +476,12 @@ def get_config() -> InvokeAIAppConfig:
     shutil.copytree(configs_src, config.legacy_conf_path, dirs_exist_ok=True)
 
     if config.config_file_path.exists():
-        incoming_config = load_and_migrate_config(config.config_file_path)
+        config_from_file = load_and_migrate_config(config.config_file_path)
         # Clobbering here will overwrite any settings that were set via environment variables
-        config.update_config(incoming_config, clobber=False)
+        config.update_config(config_from_file, clobber=False)
     else:
-        config.write_file(config.config_file_path)
+        # We should never write env vars to the config file
+        default_config = DefaultInvokeAIAppConfig()
+        default_config.write_file(config.config_file_path, as_example=False)
 
     return config