fixing unique multi index in SchemaModel (#870)

* fixing unique multi index in SchemaModel

* fix noxfile issue

* fix noxfile issue

Co-authored-by: matt <m.bouchy@gmail.com>
Co-authored-by: cosmicBboy <niels.bantilan@gmail.com>

noxfile.py

@@ -195,6 +195,12 @@ def install_extras(
     pandas_stubs: bool = True,
 ) -> None:
     """Install dependencies."""
+
+    if isinstance(session.virtualenv, nox.virtualenv.PassthroughEnv):
+        # skip this step if there's no virtual environment specified
+        session.run("pip", "install", "-e", ".", "--no-deps")
+        return
+
     specs, pip_specs = [], []
     pandas_version = "" if pandas == "latest" else f"=={pandas}"
     for spec in REQUIRES[extra].values():

pandera/typing/config.py

@@ -34,6 +34,8 @@ class BaseConfig:  # pylint:disable=R0903
     #: coerce types of all MultiIndex components
     multiindex_coerce: bool = False
 
+    #: make sure the MultiIndex is unique along the list of columns
+    multiindex_unique = None
     #: make sure all specified columns are in validated MultiIndex -
     #: if ``"filter"``, removes indexes not specified in the schema
     multiindex_strict: StrictType = False

tests/core/test_model.py

@@ -725,6 +725,40 @@ class Config:
     assert expected == Child.to_schema()
 
 
+def test_multiindex_unique() -> None:
+    class Base(pa.SchemaModel):
+        a: Series[int]
+        idx_1: Index[str]
+        idx_2: Index[str]
+
+        class Config:
+            name = "Base schema"
+            coerce = True
+            ordered = True
+            multiindex_coerce = True
+            multiindex_strict = True
+            multiindex_unique = ["idx_1", "idx_2"]
+            multiindex_name: Optional[str] = "mi"
+            unique_column_names = True
+
+    expected = pa.DataFrameSchema(
+        columns={"a": pa.Column(int)},
+        index=pa.MultiIndex(
+            [pa.Index(str, name="idx_1"), pa.Index(str, name="idx_2")],
+            coerce=True,
+            strict=True,
+            name="mi",
+            unique=["idx_1", "idx_2"],
+        ),
+        name="Base schema",
+        coerce=True,
+        ordered=True,
+        unique_column_names=True,
+    )
+
+    assert expected == Base.to_schema()
+
+
 def test_config_docstrings() -> None:
     class Model(pa.SchemaModel):
         """foo"""