Generate runtime types from .ts file generated by kysely-codegen.

kysely-runtime.js

import { readFile, writeFile } from "node:fs/promises";
import { normalize } from "node:path";
import { inspect } from "node:util";
import { Project } from "ts-morph";

async function tryReadFile(path) {
    try {
        return await readFile(path, { encoding: "utf-8" });
    } catch {
        return null;
    }
}

/**
 * Generate runtime types from kysely-codegen file and write them to an output file.
 * @param {object} options
 * @param {string} options.srcFile - The path to the kysely-codegen file containing type definitions to generate runtime types for.
 * @param {string} options.outFile - The path to write the generated runtime types to.
 * @param {string} options.typesImport - The path to import types from, relative to outFile.
 */
export async function kyselyRuntimeTypes({ srcFile, outFile, typesImport }) {
    if (normalize(srcFile) === normalize(outFile)) {
        throw new Error(`Attempting to overwrite source file at "${srcFile}".\n`);
    }

    const banner = `/** Generated by ts-morph script do not edit. */\n\n`;
    const file = await tryReadFile(outFile);

    if (file && !file.startsWith(banner)) {
        throw new Error(`Attempting to overwrite non-generated file at "${outFile}".\n`);
    }

    const dbJs = {};
    const project = new Project().addSourceFileAtPath(srcFile);
    const dbType = project.getInterfaceOrThrow("DB");

    for (const prop of dbType.getProperties()) {
        const propName = prop.getName();
        dbJs[propName] = project
            .getInterfaceOrThrow(prop.getFirstChildByKindOrThrow(180).getText())
            .getProperties()
            .map((prop) => prop.getName());
    }

    let output = `${banner}`;
    output += `import type { DB } from '${typesImport}';\n\n`;
    output += "type DBDummy = {\n";
    output += "  readonly [K in keyof DB]: ReadonlyArray<keyof DB[K]>;\n";
    output += "}\n\n";

    output += `export const dbDummy: DBDummy = ${inspect(dbJs, { showHidden: false, compact: false })} as const;`;

    await writeFile(outFile, output, { encoding: "utf-8" });
}