feat: add MySQL support

Adds `KyselyTypegenMySQLDialect`, exported from `kysely-typegen/mysql`.

src/mysql.ts

@@ -0,0 +1,102 @@
+import { sql } from "kysely"
+
+import type { IntrospectedEnums } from "./index.ts"
+import { KyselyTypegenDialect } from "./index.ts"
+
+export class KyselyTypegenMySQLDialect extends KyselyTypegenDialect {
+  // Keys are lowercase values returned by information_schema.COLUMNS.DATA_TYPE,
+  // which is what Kysely's MysqlIntrospector forwards as column.dataType.
+  public override readonly scalars: Record<string, string> = {
+    bigint: "Int8",
+    binary: "Buffer",
+    bit: "string",
+    blob: "Buffer",
+    bool: "boolean",
+    boolean: "boolean",
+    char: "string",
+    date: "Timestamp",
+    datetime: "Timestamp",
+    decimal: "Numeric",
+    double: "number",
+    enum: "string",
+    float: "number",
+    int: "number",
+    json: "Json",
+    longblob: "Buffer",
+    longtext: "string",
+    mediumblob: "Buffer",
+    mediumint: "number",
+    mediumtext: "string",
+    numeric: "Numeric",
+    set: "string",
+    smallint: "number",
+    text: "string",
+    time: "string",
+    timestamp: "Timestamp",
+    tinyblob: "Buffer",
+    tinyint: "number",
+    tinytext: "string",
+    varbinary: "Buffer",
+    varchar: "string",
+    year: "number",
+  }
+
+  protected override async introspectEnums(): Promise<IntrospectedEnums> {
+    const rows = await this.database
+      .withoutPlugins()
+      .selectFrom("information_schema.columns as columns")
+      .select([
+        "columns.TABLE_NAME as tableName",
+        "columns.COLUMN_NAME as columnName",
+        "columns.COLUMN_TYPE as columnType",
+      ])
+      .where("columns.TABLE_SCHEMA", "=", sql`database()`)
+      .where("columns.DATA_TYPE", "in", ["enum", "set"])
+      .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))
+    }
+    return { named: [], inline }
+  }
+}
+
+/**
+ * Parses MySQL `enum(...)` / `set(...)` column type definitions into the list of declared values. MySQL doubles single quotes inside string literals.
+ *
+ * @example
+ * parseMysqlEnumColumnType("enum('a','b','c''d')") // ["a", "b", "c'd"]
+ */
+const parseMysqlEnumColumnType = (columnType: string): string[] => {
+  const open = columnType.indexOf("(")
+  const close = columnType.lastIndexOf(")")
+  if (open === -1 || close === -1 || close <= open) {
+    return []
+  }
+  const inner = columnType.slice(open + 1, close)
+  const values: string[] = []
+  let current = ""
+  let insideString = false
+  for (let index = 0; index < inner.length; index++) {
+    const character = inner[index]
+    if (insideString) {
+      if (character === "'" && inner[index + 1] === "'") {
+        current += "'"
+        index++
+        continue
+      }
+      if (character === "'") {
+        insideString = false
+        values.push(current)
+        current = ""
+        continue
+      }
+      current += character
+    } else if (character === "'") {
+      insideString = true
+    }
+  }
+  return values
+}