Correct imports and improve generation logic in SQLModelGenerator

.github/workflows/test.yml

@@ -23,6 +23,8 @@ jobs:
         cache-dependency-path: pyproject.toml
     - name: Install dependencies
       run: pip install -e .[test]
+    - name: Install sqlmodel dependency
+      run: pip install -e .[sqlmodel]
     - name: Test with pytest
       run: coverage run -m pytest
     - name: Upload Coverage

src/sqlacodegen/generators.py

@@ -292,8 +292,21 @@ def group_imports(self) -> list[list[str]]:
         stdlib_imports: list[str] = []
         thirdparty_imports: list[str] = []
 
+        has_imports: set[str] = set()
         for package in sorted(self.imports):
-            imports = ", ".join(sorted(self.imports[package]))
+            if duplicate_import := self.imports[package] & has_imports:
+                print(
+                    f"WARN: Duplicate imports `{duplicate_import}`  are detected "
+                    f"from the package `{package}` and will be filtered, "
+                    f"which may cause abnormal behavior."
+                )
+
+            current_import = sorted(
+                name for name in self.imports[package] if name not in duplicate_import
+            )
+            has_imports = has_imports | set(current_import)
+
+            imports = ", ".join(current_import)
             collection = thirdparty_imports
             if package == "__future__":
                 collection = future_imports
@@ -448,7 +461,11 @@ def render_column(
             kwargs["key"] = column.key
         if is_primary:
             kwargs["primary_key"] = True
-        if not column.nullable and not is_sole_pk and is_table:
+        if (
+            not column.nullable
+            and not is_sole_pk
+            and (is_table or isinstance(self, SQLModelGenerator))
+        ):
             kwargs["nullable"] = False
 
         if is_unique:
@@ -482,10 +499,11 @@ def render_column(
         if comment:
             kwargs["comment"] = repr(comment)
 
-        if is_table:
+        if is_table or isinstance(self, SQLModelGenerator):
             self.add_import(Column)
             return render_callable("Column", *args, kwargs=kwargs)
         else:
+            self.add_literal_import("sqlalchemy.orm", "mapped_column")
             return render_callable("mapped_column", *args, kwargs=kwargs)
 
     def render_column_type(self, coltype: object) -> str: