docs: add PGlite support

Kysely's built-in PGliteDialect uses the same introspector as PostgreSQL, so KyselyTypegenPostgresDialect works with it as-is.

.github/workflows/ci.yml

@@ -15,12 +15,12 @@ jobs:
       TZ: "Europe/Paris"
       DO_NOT_TRACK: "1"
     steps:
-      - uses: "actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd" # v6.0.2
+      - uses: "actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1" # v7.0.1
 
       - name: "Setup Node.js"
-        uses: "actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e" # v6.4.0
+        uses: "actions/setup-node@820762786026740c76f36085b0efc47a31fe5020" # v7.0.0
         with:
-          node-version: "24.15.0"
+          node-version: "24.16.0"
           cache: "npm"
       - run: "node --version"
 

.github/workflows/release.yml

@@ -17,15 +17,15 @@ jobs:
       pull-requests: "write"
       id-token: "write"
     steps:
-      - uses: "actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd" # v6.0.2
+      - uses: "actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1" # v7.0.1
         with:
           fetch-depth: 0
           persist-credentials: false
 
       - name: "Setup Node.js"
-        uses: "actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e" # v6.4.0
+        uses: "actions/setup-node@820762786026740c76f36085b0efc47a31fe5020" # v7.0.0
         with:
-          node-version: "24.15.0"
+          node-version: "24.16.0"
           registry-url: "https://registry.npmjs.org"
           package-manager-cache: false
 

README.md

@@ -16,7 +16,7 @@ Why `kysely-typegen` if there is already `kysely-codegen`? Comparison:
 | **Dependencies**              | 35 total                                 | 0 (no runtime dependencies)                                                         |
 | **Type**                      | CLI                                      | Library/Programmatic Usage                                                          |
 | **Code Size/Maintainability** | Heavy                                    | Lightweight/Simple and straightforward (string manipulation instead of complex AST) |
-| **Database Support**          | PostgreSQL, MySQL, SQLite, MSSQL, LibSQL | PostgreSQL, MySQL, SQLite (**can be easily extended to more**)                      |
+| **Database Support**          | PostgreSQL, MySQL, SQLite, MSSQL, LibSQL | PostgreSQL, PGlite, MySQL, SQLite (**can be easily extended to more**)              |
 
 `kysely-typegen` is a **library** (not a CLI), which means you are in control of where and how to run it, and is designed to be **extensible**, easy to add support for more database dialects.
 
@@ -79,6 +79,30 @@ export const database = new Kysely<DB>({ dialect })
 export const databaseTypegen = new KyselyTypegenPostgresDialect({ database })
 ```
 
+#### PGlite
+
+[PGlite](https://pglite.dev/) is PostgreSQL compiled to WebAssembly that runs in-process. Use Kysely's built-in [`PGliteDialect`](https://kysely-org.github.io/kysely-apidoc/classes/PGliteDialect.html) with `KyselyTypegenPostgresDialect`: PGlite is introspected exactly like PostgreSQL. Because `kysely-typegen` is a library, it can introspect the PGlite instance your application already uses, which a CLI cannot do.
+
+```sh
+npm install @electric-sql/pglite
+```
+
+```ts
+// database.ts
+import { PGlite } from "@electric-sql/pglite"
+import { Kysely, PGliteDialect } from "kysely"
+import { KyselyTypegenPostgresDialect } from "kysely-typegen/postgres"
+
+import type { DB } from "./codegen.ts"
+
+const dialect = new PGliteDialect({
+  pglite: new PGlite(process.env["DATABASE_PATH"] ?? "./pgdata"),
+})
+
+export const database = new Kysely<DB>({ dialect })
+export const databaseTypegen = new KyselyTypegenPostgresDialect({ database })
+```
+
 #### MySQL
 
 ```sh
@@ -168,6 +192,19 @@ const rows = await database.selectFrom("User").selectAll().execute()
 
 Fully type-safe queries derived from your actual database schema.
 
+### Column comments
+
+Column comments (`COMMENT ON COLUMN` in PostgreSQL, `COMMENT '...'` in MySQL) are emitted as JSDoc above the column, so they show up in your editor on hover:
+
+```ts
+export interface Users {
+  /** Contact email address. */
+  email: string | null
+}
+```
+
+SQLite has no column comments, so none are generated.
+
 ## Extending to other database dialects
 
 `kysely-typegen` ships with `KyselyTypegenPostgresDialect`, `KyselyTypegenMySQLDialect`, and `KyselyTypegenSQLiteDialect`, but you can add support for any database by extending the abstract `KyselyTypegenDialect` class.

package.json

@@ -41,23 +41,24 @@
     "release": "semantic-release"
   },
   "devDependencies": {
-    "@testcontainers/mysql": "12.0.0",
-    "@testcontainers/postgresql": "12.0.0",
-    "@types/better-sqlite3": "7.6.13",
-    "@types/node": "25.9.1",
-    "@types/pg": "8.20.0",
-    "better-sqlite3": "12.10.0",
-    "kysely": "0.29.2",
-    "kysely-postgres-js": "3.0.0",
-    "mysql2": "3.22.3",
-    "oxfmt": "0.51.0",
-    "oxlint": "1.66.0",
-    "oxlint-tsgolint": "0.23.0",
-    "pg": "8.21.0",
+    "@electric-sql/pglite": "0.5.8",
+    "@testcontainers/mysql": "12.2.0",
+    "@testcontainers/postgresql": "12.2.0",
+    "@types/better-sqlite3": "9.6.0",
+    "@types/node": "26.6.4",
+    "@types/pg": "8.23.1",
+    "better-sqlite3": "13.0.3",
+    "kysely": "0.29.6",
+    "kysely-postgres-js": "5.0.1",
+    "mysql2": "3.24.5",
+    "oxfmt": "0.71.0",
+    "oxlint": "1.86.0",
+    "oxlint-tsgolint": "7.0.2003",
+    "pg": "8.23.1",
     "postgres": "3.4.9",
-    "semantic-release": "25.0.3",
-    "tsdown": "0.22.0",
-    "typescript": "6.0.3"
+    "semantic-release": "25.0.9",
+    "tsdown": "0.23.0",
+    "typescript": "7.0.2"
   },
   "peerDependencies": {
     "kysely": ">=0.29.0"

src/_test/__snapshots__/mysql.test.ts.snapshot

@@ -62,10 +62,16 @@ exports[`typegen MySQL > generate types matching snapshot 1`] = `
     "}",
     "",
     "export interface Orders {",
+    "  /**",
+    "   * Total amount in cents.",
+    "   *",
+    "   * Excludes taxes.",
+    "   */",
     "  amountCents: number",
     "  createdAt: Generated<Timestamp>",
     "  currency: Generated<\\"EUR\\" | \\"GBP\\" | \\"USD\\">",
     "  id: Generated<Int8>",
+    "  /** Free text, may contain *\\\\/ characters. */",
     "  note: string | null",
     "  status: Generated<\\"cancelled\\" | \\"paid\\" | \\"pending\\" | \\"shipped\\">",
     "  userId: number",
@@ -73,6 +79,7 @@ exports[`typegen MySQL > generate types matching snapshot 1`] = `
     "",
     "export interface Users {",
     "  createdAt: Generated<Timestamp>",
+    "  /** Contact email address. */",
     "  email: string | null",
     "  id: Generated<number>",
     "  isActive: Generated<number>",

src/_test/__snapshots__/postgres.test.ts.snapshot

@@ -1,3 +1,121 @@
+exports[`typegen PGlite > generate types matching snapshot 1`] = `
+{
+  "lines": [
+    "// This file was automatically generated by \`kysely-typegen\`.",
+    "// Do not edit this file manually.",
+    "",
+    "import type { ColumnType } from \\"kysely\\"",
+    "",
+    "export type Generated<T> = T extends ColumnType<infer S, infer I, infer U> ? ColumnType<S, I | undefined, U> : ColumnType<T, T | undefined, T>",
+    "",
+    "export type Timestamp = ColumnType<Date, Date | string, Date | string>",
+    "",
+    "export type Numeric = ColumnType<string, number | string, number | string>",
+    "",
+    "export type Int8 = ColumnType<string, bigint | number | string, bigint | number | string>",
+    "",
+    "export type Json = JsonValue",
+    "",
+    "export type JsonArray = JsonValue[]",
+    "",
+    "export interface JsonObject {",
+    "  [x: string]: JsonValue | undefined",
+    "}",
+    "",
+    "export type JsonPrimitive = boolean | number | string | null",
+    "",
+    "export type JsonValue = JsonArray | JsonObject | JsonPrimitive",
+    "",
+    "export type Currency = \\"EUR\\" | \\"GBP\\" | \\"USD\\"",
+    "",
+    "export type OrderStatus = \\"cancelled\\" | \\"paid\\" | \\"pending\\" | \\"shipped\\"",
+    "",
+    "export type UserRole = \\"admin\\" | \\"guest\\" | \\"member\\"",
+    "",
+    "export interface AllTypes {",
+    "  colBit: string",
+    "  colBool: boolean",
+    "  colBoolDefault: Generated<boolean>",
+    "  colBoolNullable: boolean | null",
+    "  colBox: string",
+    "  colBpchar: string",
+    "  colBytea: Buffer",
+    "  colCidr: string",
+    "  colDate: Timestamp",
+    "  colFloat4: number",
+    "  colFloat8: number",
+    "  colInet: string",
+    "  colInt2: number",
+    "  colInt4: number",
+    "  colInt8: Int8",
+    "  colJson: Json",
+    "  colJsonb: Json",
+    "  colJsonbDefault: Generated<Json>",
+    "  colLine: string",
+    "  colLseg: string",
+    "  colMacaddr: string",
+    "  colMoney: string",
+    "  colNumeric: Numeric",
+    "  colOid: number",
+    "  colPath: string",
+    "  colPoint: unknown",
+    "  colPolygon: string",
+    "  colText: string",
+    "  colTextNullable: string | null",
+    "  colTime: string",
+    "  colTimestamp: Timestamp",
+    "  colTimestampDefault: Generated<Timestamp>",
+    "  colTimestamptz: Timestamp",
+    "  colTimetz: string",
+    "  colTsquery: string",
+    "  colTsvector: string",
+    "  colUuid: string",
+    "  colVarbit: string",
+    "  colVarchar: string",
+    "  colXml: string",
+    "  createdAt: Generated<Timestamp>",
+    "  id: Generated<string>",
+    "  updatedAt: Timestamp | null",
+    "}",
+    "",
+    "export interface Orders {",
+    "  /**",
+    "   * Total amount in cents.",
+    "   *",
+    "   * Excludes taxes.",
+    "   */",
+    "  amountCents: number",
+    "  createdAt: Generated<Timestamp>",
+    "  currency: Generated<Currency>",
+    "  id: Generated<Int8>",
+    "  /** Free text, may contain *\\\\/ characters. */",
+    "  note: string | null",
+    "  status: Generated<OrderStatus>",
+    "  userId: string",
+    "}",
+    "",
+    "export interface Users {",
+    "  createdAt: Generated<Timestamp>",
+    "  /** Contact email address. */",
+    "  email: string | null",
+    "  id: Generated<string>",
+    "  isActive: Generated<boolean>",
+    "  role: Generated<UserRole>",
+    "  username: string",
+    "}",
+    "",
+    "export interface DB {",
+    "  AllTypes: AllTypes",
+    "  Orders: Orders",
+    "  Users: Users",
+    "}"
+  ],
+  "tablesCount": 3,
+  "enumsCount": 3,
+  "inlineEnumsCount": 0
+}
+`;
+
 exports[`typegen PostgreSQL > generate types matching snapshot (kysely-postgres-js) 1`] = `
 {
   "lines": [
@@ -79,10 +197,16 @@ exports[`typegen PostgreSQL > generate types matching snapshot (kysely-postgres-
     "}",
     "",
     "export interface Orders {",
+    "  /**",
+    "   * Total amount in cents.",
+    "   *",
+    "   * Excludes taxes.",
+    "   */",
     "  amountCents: number",
     "  createdAt: Generated<Timestamp>",
     "  currency: Generated<Currency>",
     "  id: Generated<Int8>",
+    "  /** Free text, may contain *\\\\/ characters. */",
     "  note: string | null",
     "  status: Generated<OrderStatus>",
     "  userId: string",
@@ -90,6 +214,7 @@ exports[`typegen PostgreSQL > generate types matching snapshot (kysely-postgres-
     "",
     "export interface Users {",
     "  createdAt: Generated<Timestamp>",
+    "  /** Contact email address. */",
     "  email: string | null",
     "  id: Generated<string>",
     "  isActive: Generated<boolean>",
@@ -190,10 +315,16 @@ exports[`typegen PostgreSQL > generate types matching snapshot (pg) 1`] = `
     "}",
     "",
     "export interface Orders {",
+    "  /**",
+    "   * Total amount in cents.",
+    "   *",
+    "   * Excludes taxes.",
+    "   */",
     "  amountCents: number",
     "  createdAt: Generated<Timestamp>",
     "  currency: Generated<Currency>",
     "  id: Generated<Int8>",
+    "  /** Free text, may contain *\\\\/ characters. */",
     "  note: string | null",
     "  status: Generated<OrderStatus>",
     "  userId: string",
@@ -201,6 +332,7 @@ exports[`typegen PostgreSQL > generate types matching snapshot (pg) 1`] = `
     "",
     "export interface Users {",
     "  createdAt: Generated<Timestamp>",
+    "  /** Contact email address. */",
     "  email: string | null",
     "  id: Generated<string>",
     "  isActive: Generated<boolean>",

src/_test/mysql.test.ts

@@ -117,7 +117,9 @@ const createSchema = async (database: Kysely<any>): Promise<void> => {
     .addColumn("username", "varchar(50)", (column) => {
       return column.notNull().unique()
     })
-    .addColumn("email", "text")
+    .addColumn("email", "text", (column) => {
+      return column.modifyEnd(sql`comment ${sql.lit("Contact email address.")}`)
+    })
     .addColumn("role", sql`enum('admin','member','guest')`, (column) => {
       return column.notNull().defaultTo("member")
     })
@@ -144,9 +146,13 @@ const createSchema = async (database: Kysely<any>): Promise<void> => {
       return column.notNull().defaultTo("EUR")
     })
     .addColumn("amountCents", "integer", (column) => {
-      return column.notNull()
+      return column
+        .notNull()
+        .modifyEnd(sql`comment ${sql.lit("Total amount in cents.\n\nExcludes taxes.")}`)
+    })
+    .addColumn("note", "text", (column) => {
+      return column.modifyEnd(sql`comment ${sql.lit("Free text, may contain */ characters.")}`)
     })
-    .addColumn("note", "text")
     .addColumn("createdAt", "timestamp", (column) => {
       return column.notNull().defaultTo(sql`current_timestamp`)
     })

src/_test/postgres.test.ts

@@ -1,6 +1,7 @@
+import { PGlite } from "@electric-sql/pglite"
 import type { StartedPostgreSqlContainer } from "@testcontainers/postgresql"
 import { PostgreSqlContainer } from "@testcontainers/postgresql"
-import { Kysely, PostgresDialect, sql } from "kysely"
+import { Kysely, PGliteDialect, PostgresDialect, sql } from "kysely"
 import { PostgresJSDialect } from "kysely-postgres-js"
 import { after, before, describe, it } from "node:test"
 import pg from "pg"
@@ -195,6 +196,16 @@ const createSchema = async (database: Kysely<any>): Promise<void> => {
       return column.notNull().defaultTo(sql`now()`)
     })
     .execute()
+
+  await sql`comment on column ${sql.ref("Users.email")} is ${sql.lit("Contact email address.")}`.execute(
+    database,
+  )
+  await sql`comment on column ${sql.ref("Orders.amountCents")} is ${sql.lit("Total amount in cents.\n\nExcludes taxes.")}`.execute(
+    database,
+  )
+  await sql`comment on column ${sql.ref("Orders.note")} is ${sql.lit("Free text, may contain */ characters.")}`.execute(
+    database,
+  )
 }
 
 describe("typegen PostgreSQL", () => {
@@ -266,3 +277,36 @@ describe("typegen PostgreSQL", () => {
     })
   })
 })
+
+describe("typegen PGlite", () => {
+  let database: Kysely<any>
+
+  before(async () => {
+    database = new Kysely<any>({
+      dialect: new PGliteDialect({
+        pglite: new PGlite(),
+      }),
+    })
+    await createSchema(database)
+  })
+
+  after(async () => {
+    await database.destroy()
+  })
+
+  it("generate types matching snapshot", async (testContext) => {
+    // Arrange - Given
+    const databaseTypegen = new KyselyTypegenPostgresDialect({ database })
+
+    // Act - When
+    const result = await databaseTypegen.typegen()
+
+    // Assert - Then
+    testContext.assert.snapshot({
+      lines: result.lines,
+      tablesCount: result.tables.length,
+      enumsCount: result.enums.length,
+      inlineEnumsCount: result.inlineEnums.size,
+    })
+  })
+})

src/index.ts

@@ -73,6 +73,24 @@ export abstract class KyselyTypegenDialect {
     return scalars[dataType] ?? "unknown"
   }
 
+  protected formatColumnComment(comment: string): string[] {
+    const trimmedComment = comment.trim()
+    if (trimmedComment.length === 0) {
+      return []
+    }
+    const lines = trimmedComment.replaceAll("*/", "*\\/").split(/\r?\n/u)
+    if (lines.length === 1) {
+      return [`  /** ${lines[0]} */`]
+    }
+    return [
+      "  /**",
+      ...lines.map((line) => {
+        return line.length === 0 ? "   *" : `   * ${line}`
+      }),
+      "   */",
+    ]
+  }
+
   public getTablesTypegen(
     tables: TableMetadata[],
     enums: EnumMetadata[],
@@ -94,6 +112,9 @@ export abstract class KyselyTypegenDialect {
         if (column.hasDefaultValue || column.isAutoIncrementing) {
           columnType = `Generated<${columnType}>`
         }
+        if (column.comment != null) {
+          result.push(...this.formatColumnComment(column.comment))
+        }
         result.push(`  ${column.name}: ${columnType}`)
       }
       result.push("}", "")
@@ -146,14 +167,16 @@ export abstract class KyselyTypegenDialect {
     tables: TableMetadata[]
   }> {
     const [tables, { enums, inlineEnums }] = await Promise.all([this.getTables(), this.getEnums()])
-    const lines: string[] = [...PREAMBLE_LINES]
-    lines.push(...this.getEnumsTypegen(enums))
-    lines.push(...this.getTablesTypegen(tables, enums, inlineEnums))
-    lines.push("export interface DB {")
-    for (const table of tables) {
-      lines.push(`  ${table.name}: ${table.name}`)
-    }
-    lines.push("}")
+    const lines: string[] = [
+      ...PREAMBLE_LINES,
+      ...this.getEnumsTypegen(enums),
+      ...this.getTablesTypegen(tables, enums, inlineEnums),
+      "export interface DB {",
+      ...tables.map((table) => {
+        return `  ${table.name}: ${table.name}`
+      }),
+      "}",
+    ]
     return { lines, enums, inlineEnums, tables }
   }
 }

src/mysql.ts

@@ -52,12 +52,12 @@ export class KyselyTypegenMySQLDialect extends KyselyTypegenDialect {
       ])
       .where("columns.TABLE_SCHEMA", "=", sql`database()`)
       .where("columns.DATA_TYPE", "in", ["enum", "set"])
+      .$castTo<{ tableName: string; columnName: string; columnType: string }>()
       .execute()
 
     const inline = new Map<string, string[]>()
     for (const row of rows) {
-      const data = row as { tableName: string; columnName: string; columnType: string }
-      inline.set(`${data.tableName}.${data.columnName}`, parseMysqlEnumColumnType(data.columnType))
+      inline.set(`${row.tableName}.${row.columnName}`, parseMysqlEnumColumnType(row.columnType))
     }
     return { named: [], inline }
   }