introduce Serialized<O>

introduce ValueNode.serialized.

introduce eb.valSerialized.

introduce sql.valSerialized.

fix json-traversal test suite.

fix null handling @ compiler.

rename to `valJson`.

add instructions in errors.

typings test inserts.

call the new type `Json` instead, to not introduce a breaking change.

add missing json column @ Getting Started.

add `appendSerializedValue`.

site/docs/getting-started/Summary.tsx

@@ -2,11 +2,7 @@ import Admonition from '@theme/Admonition'
 import CodeBlock from '@theme/CodeBlock'
 import Link from '@docusaurus/Link'
 import { IUseADifferentDatabase } from './IUseADifferentDatabase'
-import {
-  PRETTY_DIALECT_NAMES,
-  type Dialect,
-  type PropsWithDialect,
-} from './shared'
+import { type Dialect, type PropsWithDialect } from './shared'
 
 const dialectSpecificCodeSnippets: Record<Dialect, string> = {
   postgresql: `    await db.schema.createTable('person')
@@ -17,6 +13,7 @@ const dialectSpecificCodeSnippets: Record<Dialect, string> = {
       .addColumn('created_at', 'timestamp', (cb) =>
         cb.notNull().defaultTo(sql\`now()\`)
       )
+      .addColumn('metadata', 'jsonb', (cb) => cb.notNull())
       .execute()`,
   mysql: `    await db.schema.createTable('person')
       .addColumn('id', 'integer', (cb) => cb.primaryKey().autoIncrement())
@@ -26,6 +23,7 @@ const dialectSpecificCodeSnippets: Record<Dialect, string> = {
       .addColumn('created_at', 'timestamp', (cb) =>
         cb.notNull().defaultTo(sql\`now()\`)
       )
+      .addColumn('metadata', 'json', (cb) => cb.notNull())
       .execute()`,
   // TODO: Update line 42's IDENTITY once identity(1,1) is added to core.
   mssql: `    await db.schema.createTable('person')
@@ -36,6 +34,7 @@ const dialectSpecificCodeSnippets: Record<Dialect, string> = {
       .addColumn('created_at', 'datetime', (cb) =>
         cb.notNull().defaultTo(sql\`GETDATE()\`)
       )
+      .addColumn('metadata', sql\`nvarchar(max)\`, (cb) => cb.notNull())
       .execute()`,
   sqlite: `    await db.schema.createTable('person')
       .addColumn('id', 'integer', (cb) => cb.primaryKey().autoIncrement().notNull())
@@ -45,6 +44,7 @@ const dialectSpecificCodeSnippets: Record<Dialect, string> = {
       .addColumn('created_at', 'timestamp', (cb) =>
         cb.notNull().defaultTo(sql\`current_timestamp\`)
       )
+      .addColumn('metadata', 'text', (cb) => cb.notNull())
       .execute()`,
 }
 
@@ -107,6 +107,12 @@ ${dialectSpecificCodeSnippet}
       first_name: 'Jennifer',
       last_name: 'Aniston',
       gender: 'woman',
+      metadata: sql.valJson({
+        login_at: new Date().toISOString(),
+        ip: null,
+        agent: null,
+        plan: 'free',
+      }),
     })
   })
     

site/docs/getting-started/_types.mdx

@@ -10,7 +10,7 @@ import {
   ColumnType,
   Generated,
   Insertable,
-  JSONColumnType,
+  Json,
   Selectable,
   Updateable,
 } from 'kysely'
@@ -45,12 +45,10 @@ export interface PersonTable {
   // can never be updated:
   created_at: ColumnType<Date, string | undefined, never>
 
-  // You can specify JSON columns using the `JSONColumnType` wrapper.
-  // It is a shorthand for `ColumnType<T, string, string>`, where T
-  // is the type of the JSON object/array retrieved from the database,
-  // and the insert and update types are always `string` since you're
-  // always stringifying insert/update values.
-  metadata: JSONColumnType<{
+  // You can specify JSON columns using the `Json` wrapper.
+  // When inserting/updating values of such columns, you're required to wrap the
+  // values with `eb.valJson` or `sql.valJson`.
+  metadata: Json<{
     login_at: string
     ip: string | null
     agent: string | null

src/expression/expression-builder.ts

@@ -69,7 +69,7 @@ import {
   ValTuple5,
 } from '../parser/tuple-parser.js'
 import { TupleNode } from '../operation-node/tuple-node.js'
-import { Selectable } from '../util/column-type.js'
+import { Selectable, Serialized } from '../util/column-type.js'
 import { JSONPathNode } from '../operation-node/json-path-node.js'
 import { KyselyTypeError } from '../util/type-error.js'
 import {
@@ -78,6 +78,7 @@ import {
 } from '../parser/data-type-parser.js'
 import { CastNode } from '../operation-node/cast-node.js'
 import { SelectFrom } from '../parser/select-from-parser.js'
+import { ValueNode } from '../operation-node/value-node.js'
 
 export interface ExpressionBuilder<DB, TB extends keyof DB> {
   /**
@@ -511,6 +512,44 @@ export interface ExpressionBuilder<DB, TB extends keyof DB> {
     value: VE,
   ): ExpressionWrapper<DB, TB, ExtractTypeFromValueExpression<VE>>
 
+  /**
+   * Returns a value expression that will be serialized before being passed to the database.
+   *
+   * This can be used to pass in an object/array value when inserting/updating a
+   * value to a column defined with `Json`.
+   *
+   * Default serializer function is `JSON.stringify`.
+   *
+   * ### Example
+   *
+   * ```ts
+   * import { GeneratedAlways, Json } from 'kysely'
+   *
+   * interface Database {
+   *   person: {
+   *     id: GeneratedAlways<number>
+   *     name: string
+   *     experience: Json<{ title: string; company: string }[]>
+   *     preferences: Json<{ locale: string; timezone: string }>
+   *     profile: Json<{ email_verified: boolean }>
+   *   }
+   * }
+   *
+   * const result = await db
+   *   .insertInto('person')
+   *   .values(({ valJson }) => ({
+   *     name: 'Jennifer Aniston',
+   *     experience: valJson([{ title: 'Software Engineer', company: 'Google' }]), // ✔️
+   *     preferences: valJson({ locale: 'en' }), // ❌ missing `timezone`
+   *     profile: JSON.stringify({ email_verified: true }), // ❌ doesn't match `Serialized<{ email_verified }>`
+   *   }))
+   *   .execute()
+   * ```
+   */
+  valJson<O extends object | null>(
+    obj: O,
+  ): ExpressionWrapper<DB, TB, Serialized<O>>
+
   /**
    * Creates a tuple expression.
    *
@@ -1140,6 +1179,14 @@ export function createExpressionBuilder<DB, TB extends keyof DB>(
       return new ExpressionWrapper(parseValueExpression(value))
     },
 
+    valJson<O extends object | null>(
+      value: O,
+    ): ExpressionWrapper<DB, TB, Serialized<O>> {
+      return new ExpressionWrapper(
+        ValueNode.create(value, { serialized: true }),
+      )
+    },
+
     refTuple(
       ...values: ReadonlyArray<ReferenceExpression<any, any>>
     ): ExpressionWrapper<DB, TB, any> {

src/operation-node/value-node.ts

@@ -5,6 +5,7 @@ export interface ValueNode extends OperationNode {
   readonly kind: 'ValueNode'
   readonly value: unknown
   readonly immediate?: boolean
+  readonly serialized?: boolean
 }
 
 /**
@@ -15,9 +16,10 @@ export const ValueNode = freeze({
     return node.kind === 'ValueNode'
   },
 
-  create(value: unknown): ValueNode {
+  create(value: unknown, props?: { serialized?: boolean }): ValueNode {
     return freeze({
       kind: 'ValueNode',
+      ...props,
       value,
     })
   },

src/query-compiler/default-query-compiler.ts

@@ -502,6 +502,8 @@ export class DefaultQueryCompiler
   protected override visitValue(node: ValueNode): void {
     if (node.immediate) {
       this.appendImmediateValue(node.value)
+    } else if (node.serialized) {
+      this.appendSerializedValue(node.value)
     } else {
       this.appendValue(node.value)
     }
@@ -1667,6 +1669,14 @@ export class DefaultQueryCompiler
     this.append(this.getCurrentParameterPlaceholder())
   }
 
+  protected appendSerializedValue(parameter: unknown): void {
+    if (parameter === null) {
+      this.appendValue(null)
+    } else {
+      this.appendValue(JSON.stringify(parameter))
+    }
+  }
+
   protected getLeftIdentifierWrapper(): string {
     return '"'
   }

src/raw-builder/sql.ts

@@ -6,6 +6,7 @@ import { ValueNode } from '../operation-node/value-node.js'
 import { parseStringReference } from '../parser/reference-parser.js'
 import { parseTable } from '../parser/table-parser.js'
 import { parseValueExpression } from '../parser/value-parser.js'
+import { Serialized } from '../util/column-type.js'
 import { createQueryId } from '../util/query-id.js'
 import { RawBuilder, createRawBuilder } from './raw-builder.js'
 
@@ -120,6 +121,17 @@ export interface Sql {
    */
   val<V>(value: V): RawBuilder<V>
 
+  /**
+   * `sql.valJson(value)` is a shortcut for:
+   *
+   * ```ts
+   * sql<Serialized<ValueType>>`${serializerFn(obj)}`
+   * ```
+   *
+   * Default serializer function is `JSON.stringify`.
+   */
+  valJson<O extends object | null>(value: O): RawBuilder<Serialized<O>>
+
   /**
    * @deprecated Use {@link Sql.val} instead.
    */
@@ -398,6 +410,15 @@ export const sql: Sql = Object.assign(
       })
     },
 
+    valJson<O extends object | null>(value: O): RawBuilder<Serialized<O>> {
+      return createRawBuilder({
+        queryId: createQueryId(),
+        rawNode: RawNode.createWithChild(
+          ValueNode.create(value, { serialized: true }),
+        ),
+      })
+    },
+
     value<V>(value: V): RawBuilder<V> {
       return this.val(value)
     },

src/util/column-type.ts

@@ -67,9 +67,37 @@ export type Generated<S> = ColumnType<S, S | undefined, S>
  */
 export type GeneratedAlways<S> = ColumnType<S, never, never>
 
+/**
+ * A shortcut for defining type-safe JSON columns. Inserts/updates require passing
+ * values that are wrapped with `eb.valJson` or `sql.valJson` instead of `JSON.stringify`.
+ */
+export type Json<
+  SelectType extends object | null,
+  InsertType extends Serialized<SelectType> | Extract<null, SelectType> =
+    | Serialized<SelectType>
+    | Extract<null, SelectType>,
+  UpdateType extends Serialized<SelectType> | Extract<null, SelectType> =
+    | Serialized<SelectType>
+    | Extract<null, SelectType>,
+> = ColumnType<SelectType, InsertType, UpdateType>
+
+/**
+ * A symbol that is used to brand serialized objects/arrays.
+ * @internal
+ */
+declare const SerializedBrand: unique symbol
+
+/**
+ * A type that is used to brand serialized objects/arrays.
+ */
+export type Serialized<O extends object | null> = O & {
+  readonly [SerializedBrand]: '⚠️ When you insert into or update columns of type `Json` (or similar), you should wrap your JSON value with `eb.valJson` or `sql.valJson`, instead of `JSON.stringify`. ⚠️'
+}
+
 /**
  * A shortcut for defining JSON columns, which are by default inserted/updated
  * as stringified JSON strings.
+ * @deprecated Use {@link Json} instead.
  */
 export type JSONColumnType<
   SelectType extends object | null,

test/node/src/json-traversal.test.ts

@@ -1,6 +1,6 @@
 import {
   ColumnDefinitionBuilder,
-  JSONColumnType,
+  Json,
   ParseJSONResultsPlugin,
   SqlBool,
   sql,
@@ -732,9 +732,9 @@ async function initJSONTest<D extends BuiltInDialect>(
   let db = testContext.db.withTables<{
     person_metadata: {
       person_id: number
-      website: JSONColumnType<{ url: string }>
-      nicknames: JSONColumnType<string[]>
-      profile: JSONColumnType<{
+      website: Json<{ url: string }>
+      nicknames: Json<string[]>
+      profile: Json<{
         auth: {
           roles: string[]
           last_login?: { device: string }
@@ -744,12 +744,12 @@ async function initJSONTest<D extends BuiltInDialect>(
         avatar: string | null
         tags: string[]
       }>
-      experience: JSONColumnType<
+      experience: Json<
         {
           establishment: string
         }[]
       >
-      schedule: JSONColumnType<{ name: string; time: string }[][][]>
+      schedule: Json<{ name: string; time: string }[][][]>
     }
   }>()
 
@@ -798,20 +798,20 @@ async function insertDefaultJSONDataSet(ctx: TestContext) {
 
   await ctx.db
     .insertInto('person_metadata')
-    .values(
+    .values((eb) =>
       people
         .filter((person) => person.first_name && person.last_name)
         .map((person, index) => ({
           person_id: person.id,
-          website: JSON.stringify({
+          website: eb.valJson({
             url: `https://www.${person.first_name!.toLowerCase()}${person.last_name!.toLowerCase()}.com`,
           }),
-          nicknames: JSON.stringify([
+          nicknames: eb.valJson([
             `${person.first_name![0]}.${person.last_name![0]}.`,
             `${person.first_name} the Great`,
             `${person.last_name} the Magnificent`,
           ]),
-          profile: JSON.stringify({
+          profile: eb.valJson({
             tags: ['awesome'],
             auth: {
               roles: ['contributor', 'moderator'],
@@ -823,12 +823,12 @@ async function insertDefaultJSONDataSet(ctx: TestContext) {
             },
             avatar: null,
           }),
-          experience: JSON.stringify([
+          experience: eb.valJson([
             {
               establishment: 'The University of Life',
             },
           ]),
-          schedule: JSON.stringify([[[{ name: 'Gym', time: '12:15' }]]]),
+          schedule: sql.valJson([[[{ name: 'Gym', time: '12:15' }]]]),
         })),
     )
     .execute()