Line of Dict of Elements (pals-project#14)

Overwrite validation and model dump.

Alternate implementation of pals-project#13 that does not make the Python API harder
to use.

---------

Co-authored-by: Edoardo Zoni <[email protected]>

Author: ax3l

schema/BaseElement.py

@@ -1,5 +1,5 @@
 from pydantic import BaseModel, ConfigDict
-from typing import Literal, Optional
+from typing import Literal
 
 
 class BaseElement(BaseModel):
@@ -12,5 +12,14 @@ class BaseElement(BaseModel):
     # not only when an instance of BaseElement is created
     model_config = ConfigDict(validate_assignment=True)
 
-    # Unique element name
-    name: Optional[str] = None
+    # element name
+    name: str
+
+    def model_dump(self, *args, **kwargs):
+        """This makes sure the element name property is moved out and up to a one-key dictionary"""
+        elem_dict = super().model_dump(*args, **kwargs)
+        name = elem_dict.pop("name", None)
+        if name is None:
+            raise ValueError("Element missing 'name' attribute")
+        data = [{name: elem_dict}]
+        return data

schema/Line.py

@@ -1,4 +1,4 @@
-from pydantic import BaseModel, ConfigDict, Field
+from pydantic import BaseModel, ConfigDict, Field, field_validator
 from typing import Annotated, List, Literal, Union
 
 from schema.BaseElement import BaseElement
@@ -29,6 +29,57 @@ class Line(BaseModel):
         ]
     ]
 
+    @field_validator("line", mode="before")
+    @classmethod
+    def parse_list_of_dicts(cls, value):
+        """This method inserts the key of the one-key dictionary into
+        the name attribute of the elements"""
+        if not isinstance(value, list):
+            raise TypeError("line must be a list")
+
+        if value and isinstance(value[0], BaseModel):
+            # Already a list of models; nothing to do
+            return value
+
+        # we expect a list of dicts or strings
+        elements = []
+        for item_dict in value:
+            # an element is either a reference string to another element or a dict
+            if isinstance(item_dict, str):
+                raise RuntimeError("Reference/alias elements not yet implemented")
+
+            elif isinstance(item_dict, dict):
+                if not (isinstance(item_dict, dict) and len(item_dict) == 1):
+                    raise ValueError(
+                        f"Each line element must be a dict with exactly one key, the name of the element, but we got: {item_dict!r}"
+                    )
+                [(name, fields)] = item_dict.items()
+
+                if not isinstance(fields, dict):
+                    raise ValueError(
+                        f"Value for element key '{name}' must be a dict (got {fields!r})"
+                    )
+
+            # Insert the name into the fields dict
+            fields["name"] = name
+            elements.append(fields)
+        return elements
+
+    def model_dump(self, *args, **kwargs):
+        """This makes sure the element name property is moved out and up to a one-key dictionary"""
+        # Use default dump for non-line fields
+        data = super().model_dump(*args, **kwargs)
+
+        # Reformat 'line' field as list of single-key dicts
+        new_line = []
+        for elem in self.line:
+            #  Use custom dump for each line element
+            elem_dict = elem.model_dump(**kwargs)[0]
+            new_line.append(elem_dict)
+
+        data["line"] = new_line
+        return data
+
 
 # Avoid circular import issues
 Line.model_rebuild()