Fix an exact import bug with deeper nesting (#2089)

* Fix an exact import bug with depper nesting

If a schema heirarchy was deeper than 1 level and a schema referenced
another schema at a higher level, then the exact import function would
add an extra '.'.
This change checks if `from_` is any number of '.' and prepends it
to the `import_` to maintain correct heirarchy.

* Removed an errant comment line

---------

Co-authored-by: Koudai Aono <koxudaxi@gmail.com>

datamodel_code_generator/parser/base.py

@@ -239,10 +239,11 @@ def relative(current_module: str, reference: str) -> Tuple[str, str]:
 
 
 def exact_import(from_: str, import_: str, short_name: str) -> Tuple[str, str]:
-    if from_ == '.':
+    if from_ == len(from_) * '.':
         # Prevents "from . import foo" becoming "from ..foo import Foo"
+        # or "from .. import foo" becoming "from ...foo import Foo"
         # when our imported module has the same parent
-        return f'.{import_}', short_name
+        return f'{from_}{import_}', short_name
     return f'{from_}.{import_}', short_name
 
 

docs/development-contributing.md

@@ -22,7 +22,7 @@ $ cd datamodel-code-generator
 $ curl -sSL https://install.python-poetry.org | python3 - 
 
 ## 3. Install dependencies
-$ poetry install
+$ poetry install --all-extras
 
 ## 4. Create new branch and rewrite code.
 $ git checkout -b new-branch

tests/parser/test_base.py

@@ -192,6 +192,7 @@ def test_relative(current_module: str, reference: str, val: Tuple[str, str]):
     'from_,import_,name,val',
     [
         ('.', 'mod', 'Foo', ('.mod', 'Foo')),
+        ('..', 'mod', 'Foo', ('..mod', 'Foo')),
         ('.a', 'mod', 'Foo', ('.a.mod', 'Foo')),
         ('..a', 'mod', 'Foo', ('..a.mod', 'Foo')),
         ('..a.b', 'mod', 'Foo', ('..a.b.mod', 'Foo')),