SNOW-1871198: Add support for snowflake.snowpark.functions.from_json

Author: sfc-gh-jrose

src/snowflake/snowpark/functions.py

@@ -202,6 +202,7 @@
     ColumnOrName,
     ColumnOrSqlExpr,
     LiteralType,
+    type_string_to_type_object,
 )
 from snowflake.snowpark._internal.udf_utils import check_decorator_args
 from snowflake.snowpark._internal.utils import (
@@ -6479,6 +6480,52 @@ def parse_json(e: ColumnOrName, _emit_ast: bool = True) -> Column:
     return builtin("parse_json", _emit_ast=_emit_ast)(c)
 
 
+@publicapi
+def from_json(
+    e: ColumnOrName, schema: Union[str, DataType], _emit_ast: bool = True
+) -> Column:
+    """Parses a column contains a JSON string value into a column of the type specified by schema.
+    Schema can be defined as a DataType object or as a compatible type string.
+
+    Example::
+
+        >>> from snowflake.snowpark.types import MapType, StringType
+        >>> df = session.create_dataframe([('{"key": "value"}',),], schema=["a"])
+        >>> df.select(from_json(df.a, MapType(StringType(), StringType()))).show()
+        ----------------------
+        |"from_json(""A"")"  |
+        ----------------------
+        |{                   |
+        |  "key": "value"    |
+        |}                   |
+        ----------------------
+        <BLANKLINE>
+
+    Example::
+
+        >>> df = session.create_dataframe([('[1, 2, 3]',),], schema=["b"])
+        >>> df.select(from_json(df.b, "array<integer>")).show()
+        ----------------------
+        |"from_json(""B"")"  |
+        ----------------------
+        |[                   |
+        |  1,                |
+        |  2,                |
+        |  3                 |
+        |]                   |
+        ----------------------
+        <BLANKLINE>
+    """
+    c = _to_col_if_str(e, "from_json")
+    if isinstance(schema, str):
+        schema = type_string_to_type_object(schema)
+    return (
+        parse_json(e, _emit_ast=False)
+        .cast(schema, _emit_ast=False)
+        .alias(f"from_json({c.get_name()})", _emit_ast=False)
+    )
+
+
 @publicapi
 def parse_xml(e: ColumnOrName, _emit_ast: bool = True) -> Column:
     """Parse the value of the specified column as a JSON string and returns the