Refactor/cleanup root detection (#4102)

## What type of PR is this? (check all applicable)

- [ X] Refactor
- [ ] Feature
- [ ] Bug Fix
- [ ] Optimization
- [ ] Documentation Update
- [ ] Community Node Submission


## Have you discussed this change with the InvokeAI team?
- [ ] Yes
- [ X] No, because: invisible change

      
## Have you updated all relevant documentation?
- [ X] Yes
- [ ] No


## Description

There was a problem in 3.0.1 with root resolution. If INVOKEAI_ROOT were
set to "." (or any relative path), then the location of root would
change if the code did an os.chdir() after config initialization. I
fixed this in a quick and dirty way for 3.0.1.post3.

This PR cleans up the code with a little refactoring.

## Related Tickets & Documents

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- Related Issue #
- Closes #

## QA Instructions, Screenshots, Recordings

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Please provide steps on how to test changes, any hardware or 
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## Added/updated tests?

- [ ] Yes
- [ ] No : _please replace this line with details on why tests
      have not been included_

## [optional] Are there any post deployment tasks we need to perform?

invokeai/app/services/config.py

@@ -274,7 +274,7 @@ class InvokeAISettings(BaseSettings):
     @classmethod
     def _excluded(self) -> List[str]:
         # internal fields that shouldn't be exposed as command line options
-        return ["type", "initconf", "cached_root"]
+        return ["type", "initconf"]
 
     @classmethod
     def _excluded_from_yaml(self) -> List[str]:
@@ -290,7 +290,6 @@ class InvokeAISettings(BaseSettings):
             "restore",
             "root",
             "nsfw_checker",
-            "cached_root",
         ]
 
     class Config:
@@ -356,7 +355,7 @@ class InvokeAISettings(BaseSettings):
 def _find_root() -> Path:
     venv = Path(os.environ.get("VIRTUAL_ENV") or ".")
     if os.environ.get("INVOKEAI_ROOT"):
-        root = Path(os.environ.get("INVOKEAI_ROOT")).resolve()
+        root = Path(os.environ["INVOKEAI_ROOT"])
     elif any([(venv.parent / x).exists() for x in [INIT_FILE, LEGACY_INIT_FILE]]):
         root = (venv.parent).resolve()
     else:
@@ -403,7 +402,7 @@ class InvokeAIAppConfig(InvokeAISettings):
     xformers_enabled    : bool = Field(default=True, description="Enable/disable memory-efficient attention", category='Memory/Performance')
     tiled_decode        : bool = Field(default=False, description="Whether to enable tiled VAE decode (reduces memory consumption with some performance penalty)", category='Memory/Performance')
 
-    root                : Path = Field(default=_find_root(), description='InvokeAI runtime root directory', category='Paths')
+    root                : Path = Field(default=None, description='InvokeAI runtime root directory', category='Paths')
     autoimport_dir      : Path = Field(default='autoimport', description='Path to a directory of models files to be imported on startup.', category='Paths')
     lora_dir            : Path = Field(default=None, description='Path to a directory of LoRA/LyCORIS models to be imported on startup.', category='Paths')
     embedding_dir       : Path = Field(default=None, description='Path to a directory of Textual Inversion embeddings to be imported on startup.', category='Paths')
@@ -424,7 +423,6 @@ class InvokeAIAppConfig(InvokeAISettings):
     log_level           : Literal[tuple(["debug","info","warning","error","critical"])] = Field(default="info", description="Emit logging messages at this level or  higher", category="Logging")
 
     version             : bool = Field(default=False, description="Show InvokeAI version and exit", category="Other")
-    cached_root         : Path = Field(default=None,  description="internal use only", category="DEPRECATED")
     # fmt: on
 
     def parse_args(self, argv: List[str] = None, conf: DictConfig = None, clobber=False):
@@ -472,15 +470,12 @@ class InvokeAIAppConfig(InvokeAISettings):
         """
         Path to the runtime root directory
         """
-        # we cache value of root to protect against it being '.' and the cwd changing
-        if self.cached_root:
-            root = self.cached_root
-        elif self.root:
+        if self.root:
             root = Path(self.root).expanduser().absolute()
         else:
-            root = self.find_root()
-        self.cached_root = root
-        return self.cached_root
+            root = self.find_root().expanduser().absolute()
+        self.root = root  # insulate ourselves from relative paths that may change
+        return root
 
     @property
     def root_dir(self) -> Path:

tests/test_config.py

@@ -84,6 +84,21 @@ def test_env_override():
     assert conf.max_cache_size == 20
 
 
+def test_root_resists_cwd():
+    previous = os.environ["INVOKEAI_ROOT"]
+    cwd = Path(os.getcwd()).resolve()
+
+    os.environ["INVOKEAI_ROOT"] = "."
+    conf = InvokeAIAppConfig.get_config()
+    conf.parse_args([])
+    assert conf.root_path == cwd
+
+    os.chdir("..")
+    assert conf.root_path == cwd
+    os.environ["INVOKEAI_ROOT"] = previous
+    os.chdir(cwd)
+
+
 def test_type_coercion():
     conf = InvokeAIAppConfig().get_config()
     conf.parse_args(argv=["--root=/tmp/foobar"])