Deserializer: replace pydantic

pkgs/clan-cli/clan_cli/api/serde.py

@@ -29,17 +29,19 @@ Dependencies:
 Note: This module assumes the presence of other modules and classes such as `ClanError` and `ErrorDetails` from the `clan_cli.errors` module.
 """
 
+import dataclasses
 import json
 from dataclasses import dataclass, fields, is_dataclass
 from pathlib import Path
+from types import UnionType
 from typing import (
     Any,
     TypeVar,
+    Union,
+    get_args,
+    get_origin,
 )
 
-from pydantic import TypeAdapter, ValidationError
-from pydantic_core import ErrorDetails
-
 from clan_cli.errors import ClanError
 
 
@@ -83,24 +85,136 @@ def dataclass_to_dict(obj: Any, *, use_alias: bool = True) -> Any:
 T = TypeVar("T", bound=dataclass)  # type: ignore
 
 
-def from_dict(t: type[T], data: Any) -> T:
-    """
-    Dynamically instantiate a data class from a dictionary, handling nested data classes.
-    We use dataclasses. But the deserialization logic of pydantic takes a lot of complexity.
-    """
-    adapter = TypeAdapter(t)
-    try:
-        return adapter.validate_python(
-            data,
-        )
-    except ValidationError as e:
-        fst_error: ErrorDetails = e.errors()[0]
-        if not fst_error:
-            raise ClanError(msg=str(e))
+def is_union_type(type_hint: type | UnionType) -> bool:
+    return (
+        type(type_hint) is UnionType
+        or isinstance(type_hint, UnionType)
+        or get_origin(type_hint) is Union
+    )
 
-        msg = fst_error.get("msg")
-        loc = fst_error.get("loc")
-        field_path = "Unknown"
-        if loc:
-            field_path = str(loc)
-        raise ClanError(msg=msg, location=f"{t!s}: {field_path}", description=str(e))
+
+def is_type_in_union(union_type: type | UnionType, target_type: type) -> bool:
+    if get_origin(union_type) is UnionType:
+        return any(issubclass(arg, target_type) for arg in get_args(union_type))
+    return False
+
+
+def unwrap_none_type(type_hint: type | UnionType) -> type:
+    """
+    Takes a type union and returns the first non-None type.
+    None | str
+    =>
+    str
+    """
+
+    if is_union_type(type_hint):
+        # Return the first non-None type
+        return next(t for t in get_args(type_hint) if t is not type(None))
+
+    return type_hint  # type: ignore
+
+
+JsonValue = str | float | dict[str, Any] | list[Any] | None
+
+
+def construct_field(t: type, field_value: JsonValue, loc: list[str] = []) -> Any:
+    """
+    Construct a field value from a type hint and a field value.
+    """
+    # If the field is another dataclass
+    # Field_value must be a dictionary
+    if is_dataclass(t) and isinstance(field_value, dict):
+        return from_dict(t, field_value)
+
+    # If the field expects a path
+    # Field_value must be a string
+    elif issubclass(t, Path) or is_type_in_union(t, Path):
+        if not isinstance(field_value, str):
+            raise ClanError(
+                f"Expected string, cannot construct pathlib.Path() from: {field_value} ",
+                location=f"{loc}",
+            )
+
+        return Path(field_value)
+
+    # Trivial values
+    elif t is str:
+        if not isinstance(field_value, str):
+            raise ClanError(f"Expected string, got {field_value}", location=f"{loc}")
+
+        return field_value
+
+    elif t is int and not isinstance(field_value, str):
+        return int(field_value)  # type: ignore
+    elif t is float and not isinstance(field_value, str):
+        return float(field_value)  # type: ignore
+
+    # Union types construct the first non-None type
+    elif is_union_type(t):
+        # Unwrap the union type
+        t = unwrap_none_type(t)
+        # Construct the field value
+        return construct_field(t, field_value)
+
+    # Nested types
+    # list
+    # dict
+    elif get_origin(t) is list:
+        if not isinstance(field_value, list):
+            raise ClanError(f"Expected list, got {field_value}", location=f"{loc}")
+
+        return [construct_field(get_args(t)[0], item) for item in field_value]
+    elif get_origin(t) is dict and isinstance(field_value, dict):
+        return {
+            key: construct_field(get_args(t)[1], value)
+            for key, value in field_value.items()
+        }
+
+    # Unhandled
+    else:
+        raise ClanError(f"Unhandled field type {t} with value {field_value}")
+
+
+def from_dict(t: type[T], data: dict[str, Any], path: list[str] = []) -> T:
+    """
+    type t MUST be a dataclass
+    Dynamically instantiate a data class from a dictionary, handling nested data classes.
+    """
+    if not is_dataclass(t):
+        raise ClanError(f"{t.__name__} is not a dataclass")
+
+    # Attempt to create an instance of the data_class#
+    field_values: dict[str, Any] = {}
+    required: list[str] = []
+
+    for field in fields(t):
+        if field.name.startswith("_"):
+            continue
+        # The first type in a Union
+        # str <- None | str | Path
+        field_type: type[Any] = unwrap_none_type(field.type)  # type: ignore
+        data_field_name = field.metadata.get("alias", field.name)
+
+        # Check if the field is required
+        # breakpoint()
+        if (
+            field.default is dataclasses.MISSING
+            and field.default_factory is dataclasses.MISSING
+        ):
+            required.append(field.name)
+
+        # Populate the field_values dictionary with the field value
+        # if present in the data
+        if data_field_name in data:
+            field_value = data.get(data_field_name)
+            field_values[field.name] = construct_field(field_type, field_value)
+
+    # Check that all required field are present.
+    for field_name in required:
+        if field_name not in field_values:
+            formatted_path = " ".join(path)
+            raise ClanError(
+                f"Required field missing: '{field_name}' in {t} {formatted_path}, got Value: {data}"
+            )
+
+    return t(**field_values)  # type: ignore

pkgs/clan-cli/default.nix

@@ -17,8 +17,6 @@
   setuptools,
   stdenv,
 
-  pydantic,
-
   # custom args
   clan-core-path,
   nixpkgs,
@@ -30,7 +28,6 @@
 let
   pythonDependencies = [
     argcomplete # Enables shell completions
-    pydantic # Dataclass deserialisation / validation / schemas
   ];
 
   # load nixpkgs runtime dependencies from a json file

pkgs/clan-cli/tests/test_deserializers.py

@@ -45,11 +45,11 @@ def test_nested() -> None:
     class Person:
         name: str
         # deeply nested dataclasses
+        home: Path | str | None
         age: Age
         age_list: list[Age]
         age_dict: dict[str, Age]
         # Optional field
-        home: Path | None
 
     person_dict = {
         "name": "John",