feat: add AnonymousExprError (#1816)

narwhals/_arrow/expr.py

@@ -15,6 +15,7 @@
 from narwhals._expression_parsing import reuse_series_implementation
 from narwhals.dependencies import get_numpy
 from narwhals.dependencies import is_numpy_array
+from narwhals.exceptions import AnonymousExprError
 from narwhals.exceptions import ColumnNotFoundError
 from narwhals.typing import CompliantExpr
 from narwhals.utils import Implementation
@@ -390,12 +391,9 @@ def clip(self: Self, lower_bound: Any | None, upper_bound: Any | None) -> Self:
     def over(self: Self, keys: list[str]) -> Self:
         def func(df: ArrowDataFrame) -> list[ArrowSeries]:
             if self._output_names is None:
-                msg = (
-                    "Anonymous expressions are not supported in over.\n"
-                    "Instead of `nw.all()`, try using a named expression, such as "
-                    "`nw.col('a', 'b')`\n"
-                )
-                raise ValueError(msg)
+                msg = ".over"
+                raise AnonymousExprError.from_expr_name(msg)
+
             tmp = df.group_by(*keys, drop_null_keys=False).agg(self)
             tmp = df.select(*keys).join(
                 tmp, how="left", left_on=keys, right_on=keys, suffix="_right"

narwhals/_arrow/expr_name.py

@@ -3,6 +3,8 @@
 from typing import TYPE_CHECKING
 from typing import Callable
 
+from narwhals.exceptions import AnonymousExprError
+
 if TYPE_CHECKING:
     from typing_extensions import Self
 
@@ -17,12 +19,8 @@ def keep(self: Self) -> ArrowExpr:
         root_names = self._compliant_expr._root_names
 
         if root_names is None:
-            msg = (
-                "Anonymous expressions are not supported in `.name.keep`.\n"
-                "Instead of `nw.all()`, try using a named expression, such as "
-                "`nw.col('a', 'b')`\n"
-            )
-            raise ValueError(msg)
+            msg = ".name.keep"
+            raise AnonymousExprError.from_expr_name(msg)
 
         return self._compliant_expr.__class__(
             lambda df: [
@@ -42,12 +40,8 @@ def map(self: Self, function: Callable[[str], str]) -> ArrowExpr:
         root_names = self._compliant_expr._root_names
 
         if root_names is None:
-            msg = (
-                "Anonymous expressions are not supported in `.name.map`.\n"
-                "Instead of `nw.all()`, try using a named expression, such as "
-                "`nw.col('a', 'b')`\n"
-            )
-            raise ValueError(msg)
+            msg = ".name.map"
+            raise AnonymousExprError.from_expr_name(msg)
 
         output_names = [function(str(name)) for name in root_names]
 
@@ -68,12 +62,8 @@ def map(self: Self, function: Callable[[str], str]) -> ArrowExpr:
     def prefix(self: Self, prefix: str) -> ArrowExpr:
         root_names = self._compliant_expr._root_names
         if root_names is None:
-            msg = (
-                "Anonymous expressions are not supported in `.name.prefix`.\n"
-                "Instead of `nw.all()`, try using a named expression, such as "
-                "`nw.col('a', 'b')`\n"
-            )
-            raise ValueError(msg)
+            msg = ".name.prefix"
+            raise AnonymousExprError.from_expr_name(msg)
 
         output_names = [prefix + str(name) for name in root_names]
         return self._compliant_expr.__class__(
@@ -93,12 +83,8 @@ def prefix(self: Self, prefix: str) -> ArrowExpr:
     def suffix(self: Self, suffix: str) -> ArrowExpr:
         root_names = self._compliant_expr._root_names
         if root_names is None:
-            msg = (
-                "Anonymous expressions are not supported in `.name.suffix`.\n"
-                "Instead of `nw.all()`, try using a named expression, such as "
-                "`nw.col('a', 'b')`\n"
-            )
-            raise ValueError(msg)
+            msg = ".name.suffix"
+            raise AnonymousExprError.from_expr_name(msg)
 
         output_names = [str(name) + suffix for name in root_names]
 
@@ -120,12 +106,8 @@ def to_lowercase(self: Self) -> ArrowExpr:
         root_names = self._compliant_expr._root_names
 
         if root_names is None:
-            msg = (
-                "Anonymous expressions are not supported in `.name.to_lowercase`.\n"
-                "Instead of `nw.all()`, try using a named expression, such as "
-                "`nw.col('a', 'b')`\n"
-            )
-            raise ValueError(msg)
+            msg = ".name.to_lowercase"
+            raise AnonymousExprError.from_expr_name(msg)
         output_names = [str(name).lower() for name in root_names]
 
         return self._compliant_expr.__class__(
@@ -146,12 +128,8 @@ def to_uppercase(self: Self) -> ArrowExpr:
         root_names = self._compliant_expr._root_names
 
         if root_names is None:
-            msg = (
-                "Anonymous expressions are not supported in `.name.to_uppercase`.\n"
-                "Instead of `nw.all()`, try using a named expression, such as "
-                "`nw.col('a', 'b')`\n"
-            )
-            raise ValueError(msg)
+            msg = ".name.to_uppercase"
+            raise AnonymousExprError.from_expr_name(msg)
         output_names = [str(name).upper() for name in root_names]
 
         return self._compliant_expr.__class__(

narwhals/_arrow/group_by.py

@@ -9,6 +9,7 @@
 
 from narwhals._expression_parsing import is_simple_aggregation
 from narwhals._expression_parsing import parse_into_exprs
+from narwhals.exceptions import AnonymousExprError
 from narwhals.utils import generate_temporary_column_name
 from narwhals.utils import remove_prefix
 
@@ -61,12 +62,8 @@ def agg(
         )
         for expr in exprs:
             if expr._output_names is None:
-                msg = (
-                    "Anonymous expressions are not supported in group_by.agg.\n"
-                    "Instead of `nw.all()`, try using a named expression, such as "
-                    "`nw.col('a', 'b')`\n"
-                )
-                raise ValueError(msg)
+                msg = "group_by.agg"
+                raise AnonymousExprError.from_expr_name(msg)
 
         return agg_arrow(
             self._grouped,

narwhals/_dask/expr.py

@@ -16,6 +16,7 @@
 from narwhals._dask.utils import narwhals_to_native_dtype
 from narwhals._expression_parsing import infer_new_root_output_names
 from narwhals._pandas_like.utils import native_to_narwhals_dtype
+from narwhals.exceptions import AnonymousExprError
 from narwhals.exceptions import ColumnNotFoundError
 from narwhals.exceptions import InvalidOperationError
 from narwhals.typing import CompliantExpr
@@ -690,12 +691,8 @@ def gather_every(self: Self, n: int, offset: int = 0) -> NoReturn:
     def over(self: Self, keys: list[str]) -> Self:
         def func(df: DaskLazyFrame) -> list[Any]:
             if self._output_names is None:
-                msg = (
-                    "Anonymous expressions are not supported in over.\n"
-                    "Instead of `nw.all()`, try using a named expression, such as "
-                    "`nw.col('a', 'b')`\n"
-                )
-                raise ValueError(msg)
+                msg = "over"
+                raise AnonymousExprError.from_expr_name(msg)
 
             if df._native_frame.npartitions == 1:  # pragma: no cover
                 tmp = df.group_by(*keys, drop_null_keys=False).agg(self)

narwhals/_dask/expr_name.py

@@ -3,6 +3,8 @@
 from typing import TYPE_CHECKING
 from typing import Callable
 
+from narwhals.exceptions import AnonymousExprError
+
 if TYPE_CHECKING:
     from typing_extensions import Self
 
@@ -17,12 +19,8 @@ def keep(self: Self) -> DaskExpr:
         root_names = self._compliant_expr._root_names
 
         if root_names is None:
-            msg = (
-                "Anonymous expressions are not supported in `.name.keep`.\n"
-                "Instead of `nw.all()`, try using a named expression, such as "
-                "`nw.col('a', 'b')`\n"
-            )
-            raise ValueError(msg)
+            msg = ".name.keep"
+            raise AnonymousExprError.from_expr_name(msg)
 
         return self._compliant_expr.__class__(
             lambda df: [
@@ -43,12 +41,8 @@ def map(self: Self, function: Callable[[str], str]) -> DaskExpr:
         root_names = self._compliant_expr._root_names
 
         if root_names is None:
-            msg = (
-                "Anonymous expressions are not supported in `.name.map`.\n"
-                "Instead of `nw.all()`, try using a named expression, such as "
-                "`nw.col('a', 'b')`\n"
-            )
-            raise ValueError(msg)
+            msg = ".name.map"
+            raise AnonymousExprError.from_expr_name(msg)
 
         output_names = [function(str(name)) for name in root_names]
 
@@ -70,12 +64,8 @@ def map(self: Self, function: Callable[[str], str]) -> DaskExpr:
     def prefix(self: Self, prefix: str) -> DaskExpr:
         root_names = self._compliant_expr._root_names
         if root_names is None:
-            msg = (
-                "Anonymous expressions are not supported in `.name.prefix`.\n"
-                "Instead of `nw.all()`, try using a named expression, such as "
-                "`nw.col('a', 'b')`\n"
-            )
-            raise ValueError(msg)
+            msg = ".name.prefix"
+            raise AnonymousExprError.from_expr_name(msg)
 
         output_names = [prefix + str(name) for name in root_names]
         return self._compliant_expr.__class__(
@@ -96,12 +86,8 @@ def prefix(self: Self, prefix: str) -> DaskExpr:
     def suffix(self: Self, suffix: str) -> DaskExpr:
         root_names = self._compliant_expr._root_names
         if root_names is None:
-            msg = (
-                "Anonymous expressions are not supported in `.name.suffix`.\n"
-                "Instead of `nw.all()`, try using a named expression, such as "
-                "`nw.col('a', 'b')`\n"
-            )
-            raise ValueError(msg)
+            msg = ".name.suffix"
+            raise AnonymousExprError.from_expr_name(msg)
 
         output_names = [str(name) + suffix for name in root_names]
 
@@ -124,12 +110,8 @@ def to_lowercase(self: Self) -> DaskExpr:
         root_names = self._compliant_expr._root_names
 
         if root_names is None:
-            msg = (
-                "Anonymous expressions are not supported in `.name.to_lowercase`.\n"
-                "Instead of `nw.all()`, try using a named expression, such as "
-                "`nw.col('a', 'b')`\n"
-            )
-            raise ValueError(msg)
+            msg = ".name.to_lowercase"
+            raise AnonymousExprError.from_expr_name(msg)
         output_names = [str(name).lower() for name in root_names]
 
         return self._compliant_expr.__class__(
@@ -151,12 +133,8 @@ def to_uppercase(self: Self) -> DaskExpr:
         root_names = self._compliant_expr._root_names
 
         if root_names is None:
-            msg = (
-                "Anonymous expressions are not supported in `.name.to_uppercase`.\n"
-                "Instead of `nw.all()`, try using a named expression, such as "
-                "`nw.col('a', 'b')`\n"
-            )
-            raise ValueError(msg)
+            msg = ".name.to_uppercase"
+            raise AnonymousExprError.from_expr_name(msg)
         output_names = [str(name).upper() for name in root_names]
 
         return self._compliant_expr.__class__(

narwhals/_dask/group_by.py

@@ -8,6 +8,7 @@
 
 from narwhals._expression_parsing import is_simple_aggregation
 from narwhals._expression_parsing import parse_into_exprs
+from narwhals.exceptions import AnonymousExprError
 from narwhals.utils import remove_prefix
 
 if TYPE_CHECKING:
@@ -110,12 +111,8 @@ def agg(
         output_names: list[str] = copy(self._keys)
         for expr in exprs:
             if expr._output_names is None:
-                msg = (
-                    "Anonymous expressions are not supported in group_by.agg.\n"
-                    "Instead of `nw.all()`, try using a named expression, such as "
-                    "`nw.col('a', 'b')`\n"
-                )
-                raise ValueError(msg)
+                msg = "group_by.agg"
+                raise AnonymousExprError.from_expr_name(msg)
 
             output_names.extend(expr._output_names)
 

narwhals/_duckdb/group_by.py

@@ -4,6 +4,7 @@
 from typing import TYPE_CHECKING
 
 from narwhals._expression_parsing import parse_into_exprs
+from narwhals.exceptions import AnonymousExprError
 
 if TYPE_CHECKING:
     from narwhals._duckdb.dataframe import DuckDBLazyFrame
@@ -33,12 +34,8 @@ def agg(
         output_names: list[str] = copy(self._keys)
         for expr in exprs:
             if expr._output_names is None:  # pragma: no cover
-                msg = (
-                    "Anonymous expressions are not supported in group_by.agg.\n"
-                    "Instead of `nw.all()`, try using a named expression, such as "
-                    "`nw.col('a', 'b')`\n"
-                )
-                raise ValueError(msg)
+                msg = "group_by.agg"
+                raise AnonymousExprError.from_expr_name(msg)
 
             output_names.extend(expr._output_names)
 

narwhals/_pandas_like/expr.py

@@ -16,6 +16,7 @@
 from narwhals._pandas_like.utils import rename
 from narwhals.dependencies import get_numpy
 from narwhals.dependencies import is_numpy_array
+from narwhals.exceptions import AnonymousExprError
 from narwhals.exceptions import ColumnNotFoundError
 from narwhals.typing import CompliantExpr
 
@@ -399,12 +400,8 @@ def func(df: PandasLikeDataFrame) -> list[PandasLikeSeries]:
                     self._output_names is None or self._root_names is None
                 ):  # pragma: no cover
                     # Technically unreachable, but keep this for safety
-                    msg = (
-                        "Anonymous expressions are not supported in over.\n"
-                        "Instead of `nw.all()`, try using a named expression, such as "
-                        "`nw.col('a', 'b')`\n"
-                    )
-                    raise ValueError(msg)
+                    msg = "over"
+                    raise AnonymousExprError.from_expr_name(msg)
 
                 reverse = self._kwargs.get("reverse", False)
                 if reverse:
@@ -452,12 +449,8 @@ def func(df: PandasLikeDataFrame) -> list[PandasLikeSeries]:
 
             def func(df: PandasLikeDataFrame) -> list[PandasLikeSeries]:
                 if self._output_names is None:
-                    msg = (
-                        "Anonymous expressions are not supported in over.\n"
-                        "Instead of `nw.all()`, try using a named expression, such as "
-                        "`nw.col('a', 'b')`\n"
-                    )
-                    raise ValueError(msg)
+                    msg = "over"
+                    raise AnonymousExprError.from_expr_name(msg)
                 tmp = df.group_by(*keys, drop_null_keys=False).agg(self)
                 tmp = df.select(*keys).join(
                     tmp, how="left", left_on=keys, right_on=keys, suffix="_right"