Implement EF.Function.JsonPathExists (#3770)

Closes #3733

Author: roji

src/EFCore.PG/Query/Internal/NpgsqlSqlTranslatingExpressionVisitor.cs

@@ -402,6 +402,44 @@ protected override Expression VisitMethodCall(MethodCallExpression methodCallExp
                         _ => throw new UnreachableException()
                     });
             }
+
+            // We translate EF.Functions.JsonPathExists here and not in a method translator since we need to support JsonPathExists over
+            // complex and owned JSON properties, which requires special handling.
+            case nameof(RelationalDbFunctionsExtensions.JsonPathExists)
+                when declaringType == typeof(RelationalDbFunctionsExtensions)
+                    && @object is null
+                    && arguments is [_, var json, var path]:
+            {
+                if (Translate(path) is not SqlExpression translatedPath)
+                {
+                    return QueryCompilationContext.NotTranslatedExpression;
+                }
+
+#pragma warning disable EF1001 // TranslateProjection() is pubternal
+                var translatedJson = TranslateProjection(json) switch
+                {
+                    // The JSON argument is a scalar string property
+                    SqlExpression scalar => scalar,
+
+                    // The JSON argument is a complex or owned JSON property
+                    RelationalStructuralTypeShaperExpression { ValueBufferExpression: JsonQueryExpression { JsonColumn: var c } } => c,
+
+                    _ => null
+                };
+#pragma warning restore EF1001
+
+                return translatedJson is null
+                    ? QueryCompilationContext.NotTranslatedExpression
+                    : _sqlExpressionFactory.Function(
+                        "JSON_EXISTS",
+                        [translatedJson, translatedPath],
+                        nullable: true,
+                        // Note that JSON_EXISTS() does propagate nullability; however, our query pipeline assumes that if
+                        // arguments propagate nullability, that's the *only* reason for the function to return null; this means that
+                        // if the arguments are non-nullable, the IS NOT NULL wrapping check can be optimized away.
+                        argumentsPropagateNullability: [false, false],
+                        typeof(bool));
+            }
         }
 
         return QueryCompilationContext.NotTranslatedExpression;

test/EFCore.PG.FunctionalTests/Query/JsonDomQueryTest.cs

@@ -504,8 +504,7 @@ public void JsonExists()
     {
         using var ctx = CreateContext();
         var count = ctx.JsonbEntities.Count(
-            e =>
-                NpgsqlJsonDbFunctionsExtensions.JsonExists(EF.Functions, e.CustomerElement.GetProperty("Statistics"), "Visits"));
+            e => EF.Functions.JsonExists(e.CustomerElement.GetProperty("Statistics"), "Visits"));
 
         Assert.Equal(2, count);
         AssertSql(

test/EFCore.PG.FunctionalTests/Query/JsonPocoQueryTest.cs

@@ -613,8 +613,7 @@ public void JsonExists()
     {
         using var ctx = CreateContext();
         var count = ctx.JsonbEntities.Count(
-            e =>
-                NpgsqlJsonDbFunctionsExtensions.JsonExists(EF.Functions, e.Customer.Statistics, "Visits"));
+            e => EF.Functions.JsonExists(e.Customer.Statistics, "Visits"));
 
         Assert.Equal(2, count);
         AssertSql(

test/EFCore.PG.FunctionalTests/Query/JsonStringQueryTest.cs

@@ -194,7 +194,7 @@ public void JsonExists()
     {
         using var ctx = CreateContext();
 
-        var count = ctx.JsonEntities.Count(e => NpgsqlJsonDbFunctionsExtensions.JsonExists(EF.Functions, e.CustomerJsonb, "Age"));
+        var count = ctx.JsonEntities.Count(e => EF.Functions.JsonExists(e.CustomerJsonb, "Age"));
 
         Assert.Equal(2, count);
 

test/EFCore.PG.FunctionalTests/Query/Translations/JsonTranslationsNpgsqlTest.cs

@@ -9,28 +9,43 @@ public JsonTranslationsNpgsqlTest(JsonTranslationsQueryNpgsqlFixture fixture, IT
         Fixture.TestSqlLoggerFactory.SetTestOutputHelper(testOutputHelper);
     }
 
+    [MinimumPostgresVersion(17, 0)]
     public override async Task JsonPathExists_on_scalar_string_column()
     {
-        // TODO: #3733
-        await AssertTranslationFailed(base.JsonPathExists_on_scalar_string_column);
+        await base.JsonPathExists_on_scalar_string_column();
 
-        AssertSql();
+        AssertSql(
+            """
+SELECT j."Id", j."JsonString", j."JsonComplexType", j."JsonOwnedType"
+FROM "JsonEntities" AS j
+WHERE JSON_EXISTS(j."JsonString", '$.OptionalInt')
+""");
     }
 
+    [MinimumPostgresVersion(17, 0)]
     public override async Task JsonPathExists_on_complex_property()
     {
-        // TODO: #3733
-        await AssertTranslationFailed(base.JsonPathExists_on_complex_property);
+        await base.JsonPathExists_on_complex_property();
 
-        AssertSql();
+        AssertSql(
+            """
+SELECT j."Id", j."JsonString", j."JsonComplexType", j."JsonOwnedType"
+FROM "JsonEntities" AS j
+WHERE JSON_EXISTS(j."JsonComplexType", '$.OptionalInt')
+""");
     }
 
+    [MinimumPostgresVersion(17, 0)]
     public override async Task JsonPathExists_on_owned_entity()
     {
-        // TODO: #3733
-        await AssertTranslationFailed(base.JsonPathExists_on_owned_entity);
+        await base.JsonPathExists_on_owned_entity();
 
-        AssertSql();
+        AssertSql(
+            """
+SELECT j."Id", j."JsonString", j."JsonComplexType", j."JsonOwnedType"
+FROM "JsonEntities" AS j
+WHERE JSON_EXISTS(j."JsonOwnedType", '$.OptionalInt')
+""");
     }
 
     public class JsonTranslationsQueryNpgsqlFixture : JsonTranslationsQueryFixtureBase, ITestSqlLoggerFactory