add test;

changes are necessary only in postgres driver
 it's the only one where typeorm support default value for json fields

src/drivers/MssqlDriver.ts

@@ -520,6 +520,6 @@ WHERE TABLE_TYPE='BASE TABLE' and TABLE_SCHEMA in (${schema}) AND TABLE_CATALOG
             defaultValue = defaultValue.slice(1, -1);
         }
 
-        return `() => \`${defaultValue}\``;
+        return `() => "${defaultValue}"`;
     }
 }

src/drivers/MysqlDriver.ts

@@ -530,6 +530,6 @@ export default class MysqlDriver extends AbstractDriver {
             return `() => ['${defaultValue.split(",").join("','")}']`;
         }
 
-        return `() => \`${defaultValue}\``;
+        return `() => "'${defaultValue}'"`;
     }
 }

src/drivers/OracleDriver.ts

@@ -417,6 +417,6 @@ export default class OracleDriver extends AbstractDriver {
             defaultVal = defaultVal.slice(0, -1);
         }
 
-        return `() => \`${defaultVal}\``;
+        return `() => "${defaultVal}"`;
     }
 }

src/drivers/PostgresDriver.ts

@@ -103,7 +103,8 @@ export default class PostgresDriver extends AbstractDriver {
                     const defaultValue = generated
                         ? undefined
                         : PostgresDriver.ReturnDefaultValueFunction(
-                              resp.column_default
+                              resp.column_default,
+                              resp.data_type
                           );
 
                     const columnTypes = this.MatchColumnTypes(
@@ -648,7 +649,8 @@ export default class PostgresDriver extends AbstractDriver {
     }
 
     private static ReturnDefaultValueFunction(
-        defVal: string | null
+        defVal: string | null,
+        dataType: string
     ): string | undefined {
         let defaultValue = defVal;
         if (!defaultValue) {
@@ -656,6 +658,9 @@ export default class PostgresDriver extends AbstractDriver {
         }
         defaultValue = defaultValue.replace(/'::[\w ]*/, "'");
 
-        return `() => \`${defaultValue}\``;
+        if (["json", "jsonb"].some(x => x === dataType)) {
+            return `${defaultValue.slice(1, defaultValue.length - 1)}`;
+        }
+        return `() => "${defaultValue}"`;
     }
 }

src/drivers/SqliteDriver.ts

@@ -437,6 +437,6 @@ export default class SqliteDriver extends AbstractDriver {
             return undefined;
         }
 
-        return `() => \`${defVal}\``;
+        return `() => "${defVal}"`;
     }
 }

test/integration/github-issues/248/entity/Post.ts

@@ -0,0 +1,22 @@
+import { PrimaryGeneratedColumn, Column, Entity, OneToOne, JoinColumn, Index } from "typeorm";
+
+@Entity("Post")
+export class Post {
+
+    @PrimaryGeneratedColumn()
+    id: number;
+
+    @Column("json", {
+        default: { type: null, values: true }
+    })
+    data: object;
+
+    @Column("jsonb", {
+        default: { type: null, values: true }
+    })
+    data2: object;
+
+    @Column()
+    text: string;
+
+}

test/integration/runTestsFromPath.test.ts

@@ -132,6 +132,10 @@ function runTestForMultipleDrivers(
                 return dbDrivers.filter(dbDriver =>
                     ["mysql", "mariadb"].includes(dbDriver)
                 );
+            case "248":
+                return dbDrivers.filter(dbDriver =>
+                    dbDriver === "postgres"
+                );
             default:
                 return dbDrivers;
         }