Fix JSON operations directly on the root (column)

Fixes npgsql#1415
roji · Jun 12, 2020 · eda8129 · eda8129
1 parent 91c2432
commit eda8129
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Showing 3 changed files with 41 additions and 13 deletions.
diff --git a/src/EFCore.PG/Query/ExpressionTranslators/Internal/NpgsqlJsonDomTranslator.cs b/src/EFCore.PG/Query/ExpressionTranslators/Internal/NpgsqlJsonDomTranslator.cs
@@ -76,15 +76,20 @@ public virtual SqlExpression Translate(SqlExpression instance, MethodInfo method
                 return null;
             }
 
+            // The root of the JSON expression is a ColumnExpression. We wrap that with an empty traversal
+            // expression (col #>> '{}'); subsequent traversals will gradually append the path into that.
+            // Note that it's possible to call methods such as GetString() directly on the root, and the
+            // empty traversal is necessary to properly convert it to a text.
+            instance = instance is ColumnExpression columnExpression
+                ? _sqlExpressionFactory.JsonTraversal(
+                    columnExpression, returnsText: false, typeof(string), mapping)
+                : instance;
+
             if (method == GetProperty || method == ArrayIndexer)
             {
-                // The first time we see a JSON traversal it's on a column - create a JsonTraversalExpression.
-                // Traversals on top of that get appended into the same expression.
-                return instance is ColumnExpression columnExpression
-                    ? _sqlExpressionFactory.JsonTraversal(columnExpression, arguments, false, typeof(string), mapping)
-                    : instance is PostgresJsonTraversalExpression prevPathTraversal
-                        ? prevPathTraversal.Append(_sqlExpressionFactory.ApplyDefaultTypeMapping(arguments[0]))
-                        : null;
+                return instance is PostgresJsonTraversalExpression prevPathTraversal
+                    ? prevPathTraversal.Append(_sqlExpressionFactory.ApplyDefaultTypeMapping(arguments[0]))
+                    : null;
             }
 
             if (GetMethods.Contains(method.Name) &&

diff --git a/src/EFCore.PG/Query/Internal/NpgsqlSqlExpressionFactory.cs b/src/EFCore.PG/Query/Internal/NpgsqlSqlExpressionFactory.cs
@@ -96,6 +96,13 @@ public virtual PostgresILikeExpression ILike(
             [CanBeNull] SqlExpression escapeChar = null)
             => (PostgresILikeExpression)ApplyDefaultTypeMapping(new PostgresILikeExpression(match, pattern, escapeChar, null));
 
+        public virtual PostgresJsonTraversalExpression JsonTraversal(
+            [NotNull] SqlExpression expression,
+            bool returnsText,
+            [NotNull] Type type,
+            [CanBeNull] RelationalTypeMapping typeMapping = null)
+            => JsonTraversal(expression, Array.Empty<SqlExpression>(), returnsText, type, typeMapping);
+
         public virtual PostgresJsonTraversalExpression JsonTraversal(
             [NotNull] SqlExpression expression,
             [NotNull] IEnumerable<SqlExpression> path,

diff --git a/test/EFCore.PG.FunctionalTests/Query/JsonDomQueryTest.cs b/test/EFCore.PG.FunctionalTests/Query/JsonDomQueryTest.cs
@@ -347,6 +347,19 @@ WHERE CAST(j.""CustomerElement""#>>'{Statistics,Nested,SomeNullableGuid}' AS uui
 LIMIT 2");
         }
 
+        [Fact] // #1415
+        public void Where_root_value()
+        {
+            using var ctx = CreateContext();
+            _ = ctx.JsonbEntities.Single(e => e.CustomerElement.GetString() == "foo");
+
+            AssertSql(
+                @"SELECT j.""Id"", j.""CustomerDocument"", j.""CustomerElement""
+FROM ""JsonbEntities"" AS j
+WHERE j.""CustomerElement""#>>'{}' = 'foo'
+LIMIT 2");
+        }
+
         #region Functions
 
         [Fact]
@@ -501,15 +514,16 @@ public JsonDomQueryContext(DbContextOptions options) : base(options) {}
 
             public static void Seed(JsonDomQueryContext context)
             {
-                var customer1 = CreateCustomer1();
-                var customer2 = CreateCustomer2();
+                var (customer1, customer2, customer3) = (CreateCustomer1(), CreateCustomer2(), CreateCustomer3());
 
                 context.JsonbEntities.AddRange(
-                    new JsonbEntity { Id = 1, CustomerDocument = customer1, CustomerElement = customer1.RootElement},
-                    new JsonbEntity { Id = 2, CustomerDocument = customer2, CustomerElement = customer2.RootElement});
+                    new JsonbEntity { Id = 1, CustomerDocument = customer1, CustomerElement = customer1.RootElement },
+                    new JsonbEntity { Id = 2, CustomerDocument = customer2, CustomerElement = customer2.RootElement },
+                    new JsonbEntity { Id = 3, CustomerDocument = customer3, CustomerElement = customer3.RootElement });
                 context.JsonEntities.AddRange(
-                    new JsonEntity { Id = 1, CustomerDocument = customer1, CustomerElement = customer1.RootElement},
-                    new JsonEntity { Id = 2, CustomerDocument = customer2, CustomerElement = customer2.RootElement});
+                    new JsonEntity { Id = 1, CustomerDocument = customer1, CustomerElement = customer1.RootElement },
+                    new JsonEntity { Id = 2, CustomerDocument = customer2, CustomerElement = customer2.RootElement },
+                    new JsonEntity { Id = 3, CustomerDocument = customer3, CustomerElement = customer3.RootElement });
                 context.SaveChanges();
 
                 static JsonDocument CreateCustomer1() => JsonDocument.Parse(@"
@@ -572,6 +586,8 @@ static JsonDocument CreateCustomer2() => JsonDocument.Parse(@"
                         }
                     ]
                 }");
+
+                static JsonDocument CreateCustomer3() => JsonDocument.Parse(@"""foo""");
             }
         }