address PR comments

Author: Michael Lee

sqlglot/dialects/databricks.py

@@ -5,8 +5,6 @@
 
 from sqlglot import exp, transforms, jsonpath, parser
 from sqlglot.dialects.dialect import (
-    array_append_sql,
-    build_array_append_with_null_propagation,
     date_delta_sql,
     build_date_delta,
     timestamptrunc_sql,
@@ -57,7 +55,6 @@ class Parser(Spark.Parser):
 
         FUNCTIONS = {
             **Spark.Parser.FUNCTIONS,
-            "ARRAY_APPEND": build_array_append_with_null_propagation,
             "GETDATE": exp.CurrentTimestamp.from_arg_list,
             "DATEADD": build_date_delta(exp.DateAdd),
             "DATE_ADD": build_date_delta(exp.DateAdd),
@@ -105,7 +102,6 @@ class Generator(Spark.Generator):
 
         TRANSFORMS = {
             **Spark.Generator.TRANSFORMS,
-            exp.ArrayAppend: array_append_sql,
             exp.DateAdd: date_delta_sql("DATEADD"),
             exp.DateDiff: date_delta_sql("DATEDIFF"),
             exp.DatetimeAdd: lambda self, e: self.func(

sqlglot/dialects/dialect.py

@@ -1356,22 +1356,41 @@ def build_array_append_with_null_propagation(args: t.List) -> exp.ArrayAppend:
     )
 
 
-def array_append_sql(self: Generator, expression: exp.ArrayAppend) -> str:
+def array_append_with_null_propagation_sql(self: Generator, expression: exp.ArrayAppend) -> str:
     """
     Transpile ARRAY_APPEND to dialects that propagate NULL values by default.
     When transpiling from a dialect that does not propagate NULLs like DuckDB/Postgres,
     explicitly handle the NULL case using COALESCE.
     """
-    if expression.args.get("null_propagation"):
-        return self.func("ARRAY_APPEND", expression.this, expression.expression)
+    this = expression.this
+    if not expression.args.get("null_propagation"):
+        this = exp.Coalesce(expressions=[expression.this, exp.Array(expressions=[])])
 
     return self.func(
         "ARRAY_APPEND",
-        exp.Coalesce(expressions=[expression.this, exp.Array(expressions=[])]),
+        this,
         expression.expression,
     )
 
 
+def array_append_without_null_propagation_sql(self: Generator, expression: exp.ArrayAppend) -> str:
+    """
+    Transpile ARRAY_APPEND to dialects that do not propagate NULL values by default.
+    When transpiling from a dialect that propagates NULLs like Databricks/Spark/Snowflake,
+    explicitly handle the NULL case using CASE.
+    """
+    func_sql = self.func("LIST_APPEND", expression.this, expression.expression)
+
+    if not expression.args.get("null_propagation"):
+        return func_sql
+
+    if_expr = exp.If(
+        this=exp.Is(this=expression.this, expression=exp.Null()), true=exp.Null(), false=func_sql
+    )
+
+    return self.sql(if_expr)
+
+
 def var_map_sql(
     self: Generator, expression: exp.Map | exp.VarMap, map_func_name: str = "MAP"
 ) -> str:

sqlglot/dialects/snowflake.py

@@ -6,7 +6,7 @@
 from sqlglot.dialects.dialect import (
     Dialect,
     NormalizationStrategy,
-    array_append_sql,
+    array_append_with_null_propagation_sql,
     build_array_append_with_null_propagation,
     build_timetostr_or_tochar,
     build_like,
@@ -1497,7 +1497,7 @@ class Generator(generator.Generator):
             exp.ArgMin: rename_func("MIN_BY"),
             exp.Array: transforms.preprocess([transforms.inherit_struct_field_names]),
             exp.ArrayConcat: lambda self, e: self.arrayconcat_sql(e, name="ARRAY_CAT"),
-            exp.ArrayAppend: array_append_sql,
+            exp.ArrayAppend: array_append_with_null_propagation_sql,
             exp.ArrayContains: lambda self, e: self.func(
                 "ARRAY_CONTAINS",
                 e.expression

sqlglot/dialects/spark.py

@@ -4,7 +4,7 @@
 
 from sqlglot import exp
 from sqlglot.dialects.dialect import (
-    array_append_sql,
+    array_append_with_null_propagation_sql,
     build_array_append_with_null_propagation,
     rename_func,
     build_like,
@@ -208,7 +208,7 @@ class Generator(Spark2.Generator):
             exp.ArrayConstructCompact: lambda self, e: self.func(
                 "ARRAY_COMPACT", self.func("ARRAY", *e.expressions)
             ),
-            exp.ArrayAppend: array_append_sql,
+            exp.ArrayAppend: array_append_with_null_propagation_sql,
             exp.BitwiseAndAgg: rename_func("BIT_AND"),
             exp.BitwiseOrAgg: rename_func("BIT_OR"),
             exp.BitwiseXorAgg: rename_func("BIT_XOR"),