From 5bdb33d40b16efae2844e1e54ae861bdcca1d72e Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Wed, 30 Oct 2024 15:07:44 +0000
Subject: [PATCH 01/17] chore(typing): Add temporary alias for `filter`

---
 altair/vegalite/v5/api.py | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index a3070acbf..f7de6ae2e 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -530,6 +530,16 @@ def check_fields_and_encodings(parameter: Parameter, field_name: str) -> bool:
 ]
 """Permitted types for `predicate`."""
 
+# FIXME: Remove before merging
+_OrigFilterType: TypeAlias = "str | Expr | Expression | Predicate | Parameter | PredicateComposition | dict[str, Predicate | str | list | bool]"
+"""**Temporary** alias for ``transform_filter``'s original annotation.
+
+Notes
+-----
+- Quite similar to ``_PredicateType``
+- Probably some redundant typing, that can be reduced
+"""
+
 _ComposablePredicateType: TypeAlias = Union[
     _expr_core.OperatorMixin, SelectionPredicateComposition
 ]
@@ -2949,13 +2959,7 @@ def transform_extent(
     # # E.g. {'not': alt.FieldRangePredicate(field='year', range=[1950, 1960])}
     def transform_filter(
         self,
-        filter: str
-        | Expr
-        | Expression
-        | Predicate
-        | Parameter
-        | PredicateComposition
-        | dict[str, Predicate | str | list | bool],
+        filter: _OrigFilterType,
         **kwargs: Any,
     ) -> Self:
         """

From 2efd5f81ccd1c3d5a51a8e3295c75186a3f42b60 Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Wed, 30 Oct 2024 15:10:21 +0000
Subject: [PATCH 02/17] refactor: Make `empty` a regular keyword arg

- Not planning to keep the new body of the method
- Purely fishing for the first test failure
---
 altair/vegalite/v5/api.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index f7de6ae2e..491ac96c4 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -2960,6 +2960,8 @@ def transform_extent(
     def transform_filter(
         self,
         filter: _OrigFilterType,
+        *,
+        empty: Optional[bool] = Undefined,
         **kwargs: Any,
     ) -> Self:
         """
@@ -2982,8 +2984,8 @@ def transform_filter(
         """
         if isinstance(filter, Parameter):
             new_filter: dict[str, Any] = {"param": filter.name}
-            if "empty" in kwargs:
-                new_filter["empty"] = kwargs.pop("empty")
+            if not utils.is_undefined(empty):
+                new_filter["empty"] = empty
             elif isinstance(filter.empty, bool):
                 new_filter["empty"] = filter.empty
             filter = new_filter

From d2868f83a8e064c893e1a9277660493e2fe61dfb Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Wed, 30 Oct 2024 15:15:51 +0000
Subject: [PATCH 03/17] refactor: Remove `**kwargs`

Interestingly, this doesn't break any tests,
Would indicate what I suspected in (#3657) was true
---
 altair/vegalite/v5/api.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index 491ac96c4..a30f123df 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -2962,7 +2962,6 @@ def transform_filter(
         filter: _OrigFilterType,
         *,
         empty: Optional[bool] = Undefined,
-        **kwargs: Any,
     ) -> Self:
         """
         Add a :class:`FilterTransform` to the schema.
@@ -2989,7 +2988,7 @@ def transform_filter(
             elif isinstance(filter.empty, bool):
                 new_filter["empty"] = filter.empty
             filter = new_filter
-        return self._add_transform(core.FilterTransform(filter=filter, **kwargs))
+        return self._add_transform(core.FilterTransform(filter=filter))
 
     def transform_flatten(
         self,

From 841e88799def3c232e1338b9ef9cbd729a95ccdb Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Wed, 30 Oct 2024 16:13:27 +0000
Subject: [PATCH 04/17] docs: Add note on `Predicate`

Remember discovering this during (#3427), but hadn't documented
---
 altair/vegalite/v5/api.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index a30f123df..1a7675ce8 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -538,6 +538,8 @@ def check_fields_and_encodings(parameter: Parameter, field_name: str) -> bool:
 -----
 - Quite similar to ``_PredicateType``
 - Probably some redundant typing, that can be reduced
+    - ``Predicate`` derives ``PredicateComposition``
+        - Includes all ``(Logical|Field|Parameter)...Predicate``
 """
 
 _ComposablePredicateType: TypeAlias = Union[

From 63de259f00594902ae5c79717ce471a7ce4ba05a Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Wed, 30 Oct 2024 16:24:11 +0000
Subject: [PATCH 05/17] feat(DRAFT): Adds `_transform_filter_impl`

---
 altair/vegalite/v5/api.py | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index 1a7675ce8..21a675d37 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -609,6 +609,19 @@ def _predicate_to_condition(
     return condition
 
 
+def _transform_filter_impl(
+    self: _TChart, filter: _PredicateType, *, empty: Optional[bool] = Undefined
+) -> _TChart:
+    """
+    Dummy implementation for ``TopLevelMixin.transform_filter``.
+
+    **Not tested**, using to plan out how much of the ``(condition|when)`` logic can be reused.
+    """
+    cond = _predicate_to_condition(filter, empty=empty)
+    pred = cond.get("test", cond)
+    return self._add_transform(core.FilterTransform(filter=pred))
+
+
 def _condition_to_selection(
     condition: _Condition,
     if_true: _StatementType,
@@ -5073,6 +5086,17 @@ def sphere() -> SphereGenerator:
     return core.SphereGenerator(sphere=True)
 
 
+# NOTE: Copied directly from https://github.com/vega/altair/pull/3394#discussion_r1712993394
+_TChart = TypeVar(
+    "_TChart",
+    Chart,
+    RepeatChart,
+    ConcatChart,
+    HConcatChart,
+    VConcatChart,
+    FacetChart,
+    LayerChart,
+)
 ChartType: TypeAlias = Union[
     Chart, RepeatChart, ConcatChart, HConcatChart, VConcatChart, FacetChart, LayerChart
 ]

From c22ba582d8635997921bb41d9443eaf69c0a0dde Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Wed, 30 Oct 2024 18:11:21 +0000
Subject: [PATCH 06/17] feat: Adds `transform_filter` implementation

Includes deprecation handling
---
 altair/vegalite/v5/api.py | 48 ++++++++++++---------------------------
 1 file changed, 14 insertions(+), 34 deletions(-)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index 21a675d37..cd6800464 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -609,19 +609,6 @@ def _predicate_to_condition(
     return condition
 
 
-def _transform_filter_impl(
-    self: _TChart, filter: _PredicateType, *, empty: Optional[bool] = Undefined
-) -> _TChart:
-    """
-    Dummy implementation for ``TopLevelMixin.transform_filter``.
-
-    **Not tested**, using to plan out how much of the ``(condition|when)`` logic can be reused.
-    """
-    cond = _predicate_to_condition(filter, empty=empty)
-    pred = cond.get("test", cond)
-    return self._add_transform(core.FilterTransform(filter=pred))
-
-
 def _condition_to_selection(
     condition: _Condition,
     if_true: _StatementType,
@@ -2974,9 +2961,10 @@ def transform_extent(
     # # E.g. {'not': alt.FieldRangePredicate(field='year', range=[1950, 1960])}
     def transform_filter(
         self,
-        filter: _OrigFilterType,
-        *,
+        predicate: Optional[_PredicateType] = Undefined,
+        *more_predicates: _ComposablePredicateType,
         empty: Optional[bool] = Undefined,
+        **constraints: _FieldEqualType,
     ) -> Self:
         """
         Add a :class:`FilterTransform` to the schema.
@@ -2996,14 +2984,17 @@ def transform_filter(
         self : Chart object
             returns chart to allow for chaining
         """
-        if isinstance(filter, Parameter):
-            new_filter: dict[str, Any] = {"param": filter.name}
-            if not utils.is_undefined(empty):
-                new_filter["empty"] = empty
-            elif isinstance(filter.empty, bool):
-                new_filter["empty"] = filter.empty
-            filter = new_filter
-        return self._add_transform(core.FilterTransform(filter=filter))
+        if depr_filter := constraints.pop("filter", None):
+            utils.deprecated_warn(
+                "Passing `filter` as a keyword is ambiguous.\n\n"
+                "Use a positional argument for `<5.5.0` behavior.\n"
+                "Or, `alt.datum['filter'] == ...` if referring to a column named 'filter'.",
+                version="5.5.0",
+            )
+            more_predicates = *more_predicates, t.cast(Any, depr_filter)
+        cond = _parse_when(predicate, *more_predicates, empty=empty, **constraints)
+        pred = cond.get("test", cond)
+        return self._add_transform(core.FilterTransform(filter=pred))
 
     def transform_flatten(
         self,
@@ -5086,17 +5077,6 @@ def sphere() -> SphereGenerator:
     return core.SphereGenerator(sphere=True)
 
 
-# NOTE: Copied directly from https://github.com/vega/altair/pull/3394#discussion_r1712993394
-_TChart = TypeVar(
-    "_TChart",
-    Chart,
-    RepeatChart,
-    ConcatChart,
-    HConcatChart,
-    VConcatChart,
-    FacetChart,
-    LayerChart,
-)
 ChartType: TypeAlias = Union[
     Chart, RepeatChart, ConcatChart, HConcatChart, VConcatChart, FacetChart, LayerChart
 ]

From fc672bccf1f15c310b0e882e63d07a4cfa3de48c Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Wed, 30 Oct 2024 18:14:31 +0000
Subject: [PATCH 07/17] fix(DRAFT): Add temp ignore for
 `line_chart_with_cumsum_faceted`

- Need to widen the definition of `_PredicateType`
- To support this, we'll need to model with `TypedDict`(s)
---
 .../examples_arguments_syntax/line_chart_with_cumsum_faceted.py | 2 +-
 tests/examples_methods_syntax/line_chart_with_cumsum_faceted.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/examples_arguments_syntax/line_chart_with_cumsum_faceted.py b/tests/examples_arguments_syntax/line_chart_with_cumsum_faceted.py
index 5a0fdb743..68994b0a4 100644
--- a/tests/examples_arguments_syntax/line_chart_with_cumsum_faceted.py
+++ b/tests/examples_arguments_syntax/line_chart_with_cumsum_faceted.py
@@ -12,7 +12,7 @@
 columns_sorted = ['Drought', 'Epidemic', 'Earthquake', 'Flood']
 
 alt.Chart(source).transform_filter(
-    {'and': [
+    {'and': [ # type: ignore[arg-type]
         alt.FieldOneOfPredicate(field='Entity', oneOf=columns_sorted), # Filter data to show only disasters in columns_sorted
         alt.FieldRangePredicate(field='Year', range=[1900, 2000]) # Filter data to show only 20th century
     ]}
diff --git a/tests/examples_methods_syntax/line_chart_with_cumsum_faceted.py b/tests/examples_methods_syntax/line_chart_with_cumsum_faceted.py
index d9d887ba5..459cf6011 100644
--- a/tests/examples_methods_syntax/line_chart_with_cumsum_faceted.py
+++ b/tests/examples_methods_syntax/line_chart_with_cumsum_faceted.py
@@ -12,7 +12,7 @@
 columns_sorted = ['Drought', 'Epidemic', 'Earthquake', 'Flood']
 
 alt.Chart(source).transform_filter(
-    {'and': [
+    {'and': [ # type: ignore[arg-type]
         alt.FieldOneOfPredicate(field='Entity', oneOf=columns_sorted), # Filter data to show only disasters in columns_sorted
         alt.FieldRangePredicate(field='Year', range=[1900, 2000]) # Filter data to show only 20th century
     ]}

From 8554a46efff1900d3ac9cdac910549c8c6f53997 Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Wed, 30 Oct 2024 18:37:30 +0000
Subject: [PATCH 08/17] feat(typing): Widen `_FieldEqualType` to include
 `IntoExpression`

This alias may be redundant now, need to review that later
---
 altair/vegalite/v5/api.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index cd6800464..d45286f94 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -562,7 +562,7 @@ def check_fields_and_encodings(parameter: Parameter, field_name: str) -> bool:
 """
 
 
-_FieldEqualType: TypeAlias = Union[PrimitiveValue_T, Map, Parameter, SchemaBase]
+_FieldEqualType: TypeAlias = Union["IntoExpression", Parameter, SchemaBase]
 """Permitted types for equality checks on field values:
 
 - `datum.field == ...`

From ff9d33fe773991a2db9f23d2c2e8b2e45f720908 Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Thu, 31 Oct 2024 18:56:00 +0000
Subject: [PATCH 09/17] fix: Try replacing `Undefined` first

Didn't account for a `TypeError` that can be triggered if `more_predicates` isn't composable.
E.g `filter={"field": "year", "oneOf": [1955, 2000]}`
---
 altair/vegalite/v5/api.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index d45286f94..f5b955229 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -2991,7 +2991,10 @@ def transform_filter(
                 "Or, `alt.datum['filter'] == ...` if referring to a column named 'filter'.",
                 version="5.5.0",
             )
-            more_predicates = *more_predicates, t.cast(Any, depr_filter)
+            if utils.is_undefined(predicate):
+                predicate = t.cast(Any, depr_filter)
+            else:
+                more_predicates = *more_predicates, t.cast(Any, depr_filter)
         cond = _parse_when(predicate, *more_predicates, empty=empty, **constraints)
         pred = cond.get("test", cond)
         return self._add_transform(core.FilterTransform(filter=pred))

From b49703968d9ca2a3493eaa3f7b2e7a54ed0476e2 Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Thu, 31 Oct 2024 18:58:45 +0000
Subject: [PATCH 10/17] test: Add `(*predicates, **constraints)` syntax tests

---
 tests/vegalite/v5/test_api.py | 61 ++++++++++++++++++++++++++++++++++-
 1 file changed, 60 insertions(+), 1 deletion(-)

diff --git a/tests/vegalite/v5/test_api.py b/tests/vegalite/v5/test_api.py
index ac184f86c..5e3e7a283 100644
--- a/tests/vegalite/v5/test_api.py
+++ b/tests/vegalite/v5/test_api.py
@@ -10,6 +10,7 @@
 import re
 import sys
 import tempfile
+import warnings
 from datetime import date, datetime
 from importlib.metadata import version as importlib_version
 from importlib.util import find_spec
@@ -81,7 +82,7 @@ def _make_chart_type(chart_type):
 
 
 @pytest.fixture
-def basic_chart():
+def basic_chart() -> alt.Chart:
     data = pd.DataFrame(
         {
             "a": ["A", "B", "C", "D", "E", "F", "G", "H", "I"],
@@ -1189,6 +1190,64 @@ def test_filter_transform_selection_predicates():
     ]
 
 
+def test_filter_transform_predicates(basic_chart) -> None:
+    lhs, rhs = alt.datum["b"] >= 30, alt.datum["b"] < 60
+    expected = [{"filter": lhs & rhs}]
+    actual = basic_chart.transform_filter(lhs, rhs).to_dict()["transform"]
+    assert actual == expected
+
+
+def test_filter_transform_constraints(basic_chart) -> None:
+    lhs, rhs = alt.datum["a"] == "A", alt.datum["b"] == 30
+    expected = [{"filter": lhs & rhs}]
+    actual = basic_chart.transform_filter(a="A", b=30).to_dict()["transform"]
+    assert actual == expected
+
+
+def test_filter_transform_predicates_constraints(basic_chart) -> None:
+    from functools import reduce
+    from operator import and_
+
+    predicates = (
+        alt.datum["a"] != "A",
+        alt.datum["a"] != "B",
+        alt.datum["a"] != "C",
+        alt.datum["b"] > 1,
+        alt.datum["b"] < 99,
+    )
+    constraints = {"b": 30, "a": "D"}
+    pred_constraints = *predicates, alt.datum["b"] == 30, alt.datum["a"] != "D"
+    expected = [{"filter": reduce(and_, pred_constraints)}]
+    actual = basic_chart.transform_filter(*predicates, **constraints).to_dict()[
+        "transform"
+    ]
+    assert actual == expected
+
+
+def test_filter_transform_errors(basic_chart) -> None:
+    NO_ARGS = r"At least one.+Undefined"
+    FILTER_KWARGS = r"ambiguous"
+
+    depr_filter = {"field": "year", "oneOf": [1955, 2000]}
+    expected = [{"filter": depr_filter}]
+
+    with pytest.raises(TypeError, match=NO_ARGS):
+        basic_chart.transform_filter()
+    with pytest.raises(TypeError, match=NO_ARGS):
+        basic_chart.transform_filter(empty=True)
+    with pytest.raises(TypeError, match=NO_ARGS):
+        basic_chart.transform_filter(empty=False)
+
+    with pytest.warns(alt.AltairDeprecationWarning, match=FILTER_KWARGS):
+        basic_chart.transform_filter(filter=depr_filter)
+
+    with warnings.catch_warnings():
+        warnings.filterwarnings("ignore", category=alt.AltairDeprecationWarning)
+        actual = basic_chart.transform_filter(filter=depr_filter).to_dict()["transform"]
+
+    assert actual == expected
+
+
 def test_resolve_methods():
     chart = alt.LayerChart().resolve_axis(x="shared", y="independent")
     assert chart.resolve == alt.Resolve(

From 7f6c188a299560a03eddc594294e9869ae79f0f9 Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Sun, 3 Nov 2024 21:30:05 +0000
Subject: [PATCH 11/17] docs: Use `*predicates` in "Faceted Line Chart with
 Cumulative Sum"

Makes use of #3668

Resolves https://github.com/vega/altair/pull/3664#discussion_r1823177593
---
 .../line_chart_with_cumsum_faceted.py                       | 6 ++----
 .../line_chart_with_cumsum_faceted.py                       | 6 ++----
 2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/tests/examples_arguments_syntax/line_chart_with_cumsum_faceted.py b/tests/examples_arguments_syntax/line_chart_with_cumsum_faceted.py
index 68994b0a4..d33df06ad 100644
--- a/tests/examples_arguments_syntax/line_chart_with_cumsum_faceted.py
+++ b/tests/examples_arguments_syntax/line_chart_with_cumsum_faceted.py
@@ -12,10 +12,8 @@
 columns_sorted = ['Drought', 'Epidemic', 'Earthquake', 'Flood']
 
 alt.Chart(source).transform_filter(
-    {'and': [ # type: ignore[arg-type]
-        alt.FieldOneOfPredicate(field='Entity', oneOf=columns_sorted), # Filter data to show only disasters in columns_sorted
-        alt.FieldRangePredicate(field='Year', range=[1900, 2000]) # Filter data to show only 20th century
-    ]}
+    alt.FieldOneOfPredicate(field='Entity', oneOf=columns_sorted), 
+    alt.FieldRangePredicate(field='Year', range=[1900, 2000])
 ).transform_window(
     cumulative_deaths='sum(Deaths)', groupby=['Entity'] # Calculate cumulative sum of Deaths by Entity
 ).mark_line().encode( 
diff --git a/tests/examples_methods_syntax/line_chart_with_cumsum_faceted.py b/tests/examples_methods_syntax/line_chart_with_cumsum_faceted.py
index 459cf6011..56dcdb931 100644
--- a/tests/examples_methods_syntax/line_chart_with_cumsum_faceted.py
+++ b/tests/examples_methods_syntax/line_chart_with_cumsum_faceted.py
@@ -12,10 +12,8 @@
 columns_sorted = ['Drought', 'Epidemic', 'Earthquake', 'Flood']
 
 alt.Chart(source).transform_filter(
-    {'and': [ # type: ignore[arg-type]
-        alt.FieldOneOfPredicate(field='Entity', oneOf=columns_sorted), # Filter data to show only disasters in columns_sorted
-        alt.FieldRangePredicate(field='Year', range=[1900, 2000]) # Filter data to show only 20th century
-    ]}
+    alt.FieldOneOfPredicate(field='Entity', oneOf=columns_sorted), 
+    alt.FieldRangePredicate(field='Year', range=[1900, 2000])
 ).transform_window(
     cumulative_deaths='sum(Deaths)', groupby=['Entity'] # Calculate cumulative sum of Deaths by Entity
 ).mark_line().encode( 

From be63d4e6adc9c50327be7e10421356b9d2447aa4 Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Mon, 4 Nov 2024 10:01:11 +0000
Subject: [PATCH 12/17] refactor: Remove `_OrigFilterType`

---
 altair/vegalite/v5/api.py | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index 3f59b2443..8317d568b 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -128,7 +128,6 @@
         NamedData,
         ParameterName,
         PointSelectionConfig,
-        Predicate,
         PredicateComposition,
         ProjectionType,
         RepeatMapping,
@@ -523,18 +522,6 @@ def check_fields_and_encodings(parameter: Parameter, field_name: str) -> bool:
 ]
 """Permitted types for `predicate`."""
 
-# FIXME: Remove before merging
-_OrigFilterType: TypeAlias = "str | Expr | Expression | Predicate | Parameter | PredicateComposition | dict[str, Predicate | str | list | bool]"
-"""**Temporary** alias for ``transform_filter``'s original annotation.
-
-Notes
------
-- Quite similar to ``_PredicateType``
-- Probably some redundant typing, that can be reduced
-    - ``Predicate`` derives ``PredicateComposition``
-        - Includes all ``(Logical|Field|Parameter)...Predicate``
-"""
-
 _ComposablePredicateType: TypeAlias = Union[
     _expr_core.OperatorMixin, core.PredicateComposition
 ]

From 7a0cc42a99a0e2ba4f3e9c1e662ce7dbfeece5a2 Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Mon, 4 Nov 2024 12:23:55 +0000
Subject: [PATCH 13/17] docs: Update `.transform_filter()` docstring

- Builds on the style introdcued for `alt.when`
- Shows a few specific kinds of predicates - due to the prior doc listing 5

https://github.com/vega/altair/issues/3657
---
 altair/vegalite/v5/api.py | 95 +++++++++++++++++++++++++++++++++------
 1 file changed, 81 insertions(+), 14 deletions(-)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index 8317d568b..88a313d94 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -2987,8 +2987,6 @@ def transform_extent(
         """
         return self._add_transform(core.ExtentTransform(extent=extent, param=param))
 
-    # TODO: Update docstring
-    # # E.g. {'not': alt.FieldRangePredicate(field='year', range=[1950, 1960])}
     def transform_filter(
         self,
         predicate: Optional[_PredicateType] = Undefined,
@@ -2997,22 +2995,91 @@ def transform_filter(
         **constraints: _FieldEqualType,
     ) -> Self:
         """
-        Add a :class:`FilterTransform` to the schema.
+        Add a :class:`FilterTransform` to the spec.
+
+        The resulting predicate is an ``&`` reduction over ``predicate`` and optional ``*``, ``**``, arguments.
 
         Parameters
         ----------
-        filter : a filter expression or :class:`PredicateComposition`
-            The `filter` property must be one of the predicate definitions:
-            (1) a string or alt.expr expression
-            (2) a range predicate
-            (3) a selection predicate
-            (4) a logical operand combining (1)-(3)
-            (5) a Selection object
+        predicate
+            A selection or test predicate. ``str`` input will be treated as a test operand.
+        *more_predicates
+            Additional predicates, restricted to types supporting ``&``.
+        empty
+            For selection parameters, the predicate of empty selections returns ``True`` by default.
+            Override this behavior, with ``empty=False``.
 
-        Returns
-        -------
-        self : Chart object
-            returns chart to allow for chaining
+            .. note::
+                When ``predicate`` is a ``Parameter`` that is used more than once,
+                ``self.transform_filter(..., empty=...)`` provides granular control for each occurrence.
+        **constraints
+            Specify `Field Equal Predicate`_'s.
+            Shortcut for ``alt.datum.field_name == value``, see examples for usage.
+
+        Warns
+        -----
+        AltairDeprecationWarning
+            If called using ``filter`` as a keyword argument.
+
+        See Also
+        --------
+        alt.when : Uses a similar syntax for defining conditional values.
+
+        Notes
+        -----
+        - Directly inspired by the syntax used in `polars.DataFrame.filter`_.
+
+        .. _Field Equal Predicate:
+            https://vega.github.io/vega-lite/docs/predicate.html#equal-predicate
+        .. _polars.DataFrame.filter:
+            https://docs.pola.rs/api/python/stable/reference/dataframe/api/polars.DataFrame.filter.html
+
+        Examples
+        --------
+        Setting up a common chart::
+
+            import altair as alt
+            from altair import datum
+            from vega_datasets import data
+
+            source = data.population.url
+            chart = (
+                alt.Chart(source)
+                .mark_line()
+                .encode(
+                    x="age:O",
+                    y="sum(people):Q",
+                    color=alt.Color("year:O").legend(symbolType="square"),
+                )
+            )
+            chart
+
+        Singular predicates can be expressed via ``datum``::
+
+            chart.transform_filter(datum.year <= 1980)
+
+        We can also use parameter selections directly::
+
+            selection = alt.selection_point(encodings=["color"], bind="legend")
+            chart.transform_filter(selection).add_params(selection)
+
+        Or using field predicates::
+
+            between_1950_60 = alt.FieldRangePredicate(field="year", range=[1950, 1960])
+            chart.transform_filter(between_1950_60) | chart.transform_filter(~between_1950_60)
+
+        Predicates can be composed together using logical operands::
+
+            chart.transform_filter(between_1950_60 | (datum.year == 1850))
+
+        Predicates passed as positional arguments will be reduced with ``&``::
+
+            chart.transform_filter(datum.year > 1980, datum.age != 90)
+
+        Using keyword-argument ``constraints`` can simplify compositions like::
+
+            verbose_composition = chart.transform_filter((datum.year == 2000) & (datum.sex == 1))
+            chart.transform_filter(year=2000, sex=1)
         """
         if depr_filter := constraints.pop("filter", None):
             utils.deprecated_warn(

From 08a4207eb5c8bea2632cef648acb75a535e1062d Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Mon, 4 Nov 2024 12:55:28 +0000
Subject: [PATCH 14/17] docs: Minor corrections in examples

---
 altair/vegalite/v5/api.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index 88a313d94..5a92ffe95 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -3058,12 +3058,12 @@ def transform_filter(
 
             chart.transform_filter(datum.year <= 1980)
 
-        We can also use parameter selections directly::
+        We can also use selection parameters directly::
 
             selection = alt.selection_point(encodings=["color"], bind="legend")
             chart.transform_filter(selection).add_params(selection)
 
-        Or using field predicates::
+        Or a field predicate::
 
             between_1950_60 = alt.FieldRangePredicate(field="year", range=[1950, 1960])
             chart.transform_filter(between_1950_60) | chart.transform_filter(~between_1950_60)

From 5fd4f5a355ddba87790767422df4339cd63a9499 Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Mon, 4 Nov 2024 13:05:26 +0000
Subject: [PATCH 15/17] refactor(typing): Cast deprecated `filter` in one
 location

Need to forgo all type safety here, since it would permit `_PredicateType` instead of the narrower `_FieldEqualType`
---
 altair/vegalite/v5/api.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index 5a92ffe95..15880fc85 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -3081,7 +3081,7 @@ def transform_filter(
             verbose_composition = chart.transform_filter((datum.year == 2000) & (datum.sex == 1))
             chart.transform_filter(year=2000, sex=1)
         """
-        if depr_filter := constraints.pop("filter", None):
+        if depr_filter := t.cast(Any, constraints.pop("filter", None)):
             utils.deprecated_warn(
                 "Passing `filter` as a keyword is ambiguous.\n\n"
                 "Use a positional argument for `<5.5.0` behavior.\n"
@@ -3089,9 +3089,9 @@ def transform_filter(
                 version="5.5.0",
             )
             if utils.is_undefined(predicate):
-                predicate = t.cast(Any, depr_filter)
+                predicate = depr_filter
             else:
-                more_predicates = *more_predicates, t.cast(Any, depr_filter)
+                more_predicates = *more_predicates, depr_filter
         cond = _parse_when(predicate, *more_predicates, empty=empty, **constraints)
         pred = cond.get("test", cond)
         return self._add_transform(core.FilterTransform(filter=pred))

From d640933ce1db795a0c2dd3814f761d47cb221d96 Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Mon, 4 Nov 2024 13:08:05 +0000
Subject: [PATCH 16/17] refactor: Remove `pred` assignment

I added this while trying to resolve a different typing issue, purely to see what was inferred
---
 altair/vegalite/v5/api.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index 15880fc85..6eb6b7d63 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -3093,8 +3093,7 @@ def transform_filter(
             else:
                 more_predicates = *more_predicates, depr_filter
         cond = _parse_when(predicate, *more_predicates, empty=empty, **constraints)
-        pred = cond.get("test", cond)
-        return self._add_transform(core.FilterTransform(filter=pred))
+        return self._add_transform(core.FilterTransform(filter=cond.get("test", cond)))
 
     def transform_flatten(
         self,

From 2d57d6ec74f868eb08811602475d7beb2a57fd8a Mon Sep 17 00:00:00 2001
From: dangotbanned <125183946+dangotbanned@users.noreply.github.com>
Date: Mon, 4 Nov 2024 13:17:14 +0000
Subject: [PATCH 17/17] docs(typing): Update `_FieldEqualType`

Think this makes it clearer how each of these align
---
 altair/vegalite/v5/api.py | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index 6eb6b7d63..115fe7e3c 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -543,11 +543,18 @@ def check_fields_and_encodings(parameter: Parameter, field_name: str) -> bool:
 
 
 _FieldEqualType: TypeAlias = Union["IntoExpression", Parameter, SchemaBase]
-"""Permitted types for equality checks on field values:
+"""
+Permitted types for equality checks on field values.
+
+Applies to the following context(s):
+
+    import altair as alt
 
-- `datum.field == ...`
-- `FieldEqualPredicate(equal=...)`
-- `when(**constraints=...)`
+    alt.datum.field == ...
+    alt.FieldEqualPredicate(field="field", equal=...)
+    alt.when(field=...)
+    alt.when().then().when(field=...)
+    alt.Chart.transform_filter(field=...)
 """