fix: enable explicitly inserting IDENTITY values into mssql

Allow explicit insertion of preset values for mssql IDENTITY columns. These are the equivalent to
auto-incrementing primary keys in MySQL, but require special conditional treatment.

Closes: typeorm#2199 for mssql

src/query-builder/InsertQueryBuilder.ts

@@ -335,6 +335,19 @@ export class InsertQueryBuilder<Entity> extends QueryBuilder<Entity> {
             query += ` RETURNING ${returningExpression}`;
         }
 
+
+        // Inserting a specific value for an auto-increment primary key in mssql requires enabling IDENTITY_INSERT
+        // IDENTITY_INSERT can only be enabled for tables where there is an IDENTITY column and only if there is a value to be inserted (i.e. supplying DEFAULT is prohibited if IDENTITY_INSERT is enabled)
+        if (this.connection.driver instanceof SqlServerDriver
+            && this.expressionMap.mainAlias!.hasMetadata
+            && this.expressionMap.mainAlias!.metadata.columns
+                .filter((column) => this.expressionMap.insertColumns.length > 0 ? this.expressionMap.insertColumns.indexOf(column.propertyPath) !== -1 : column.isInsert)
+                .some((column) => column.isPrimary && column.isGenerated && column.generationStrategy === "increment"
+                    && this.getValueSets().some((valueSet) => column.getEntityValue(valueSet) !== undefined && column.getEntityValue(valueSet) !== null))
+        ) {
+            query = `SET IDENTITY_INSERT ${tableName} ON; ${query}; SET IDENTITY_INSERT ${tableName} OFF`;
+        }
+
         return query;
     }
 
@@ -360,7 +373,8 @@ export class InsertQueryBuilder<Entity> extends QueryBuilder<Entity> {
                 && !(this.connection.driver instanceof OracleDriver)
                 && !(this.connection.driver instanceof AbstractSqliteDriver)
                 && !(this.connection.driver instanceof MysqlDriver)
-                && !(this.connection.driver instanceof AuroraDataApiDriver))
+                && !(this.connection.driver instanceof AuroraDataApiDriver)
+                && !(this.connection.driver instanceof SqlServerDriver && this.getValueSets().some((valueSet) => column.getEntityValue(valueSet) !== undefined && column.getEntityValue(valueSet) !== null)))
                 return false;
 
             return true;

test/github-issues/2199/issue-2199.ts

@@ -4,12 +4,12 @@ import { Connection } from "../../../src/connection/Connection";
 import { closeTestingConnections, createTestingConnections, reloadTestingDatabases } from "../../utils/test-utils";
 import { Bar } from "./entity/Bar";
 
-describe("github issues > #2199 - Inserting value for @PrimaryGeneratedColumn() for mysql and sqlite", () => {
+describe("github issues > #2199 - Inserting value for @PrimaryGeneratedColumn() for mysql, sqlite and mssql", () => {
 
     let connections: Connection[];
     before(async () => connections = await createTestingConnections({
         entities: [__dirname + "/entity/*{.js,.ts}"],
-        enabledDrivers: ["mysql", "mariadb", "sqlite"],
+        enabledDrivers: ["mysql", "mariadb", "sqlite", "mssql"],
         schemaCreate: true,
         dropSchema: true
     }));