The way I do it is pretty dumb. We have files like src/test/_template.test.ts that are valid TS, that our codegen commands like `notion new test` regex-replace

The way I do it is pretty dumb. We have files like src/test/_template.test.ts that are valid TS, that our codegen commands like `notion new test` regex-replace to “instantiate” the template. The convention we follow is to name replacement targets with double underscores. No need for some kind of specialized template library - just regex & replaceAll. The scripts that consume our templates are mostly very simple ~15 line affairs but there are a few very complex, 1000+ line affairs that use the Typescript type checker API to codegen model classes and test data generators from hand-written interface types. Those things read ASTs but writing ASTs seems like a huge waste of time to me. AST is only nice if you need to very carefully morph existing code, and even then I usually end up doing a string replacement of an AST node’s position in its original file. In all that code I think the only thing that writes using an AST is import statement stuff. Luckily that super complex stuff runs on every commit so it can’t break. It’s the one-off codegen commands like “make me a new component” or “make me an integration test” that are in danger of going stale, and even those we could write some CI tests for like “make a new thingy, check that it typechecks”. Anyways here’s a full example template file: /*__FILE_METADATA__*/ /* ================================================================================ __TEMPLATE_CLASS_NAME__. Docs: https://dev.notion.so/notion/Record-Framework-1f41f97e1cc746628a6af57ba75d75ad THIS IS FILE IS PARTIALLY GENERATED. ONLY EDIT THE EDITABLE REGION BELOW. __GENERATED_BY__ __GENERATED_FROM__ ================================================================================ */ import type { /*__VALUE_IMPORT__*/ BlockValue as __VALUE_TYPE__, /*__TABLE_IMPORT__*/ BlockTable as __TABLE__, } from /*__SCHEMA_IMPORT__*/ "../schemas/Block" import { Model } from "./Model" /*__REMOVE_LINE__*/ // : Value <Value> as __MODEL__<Value> | undefined <- Conform to template args in RecordStore. /** * This class is generated from {@link __VALUE_TYPE__}. * To customize, edit the section in {@link __TEMPLATE_CLASS_NAME__} below. */ abstract class Generated__TEMPLATE_CLASS_NAME__< Value extends __VALUE_TYPE__ = __VALUE_TYPE__ > extends Model<Value, __TABLE__> { /*__REMOVE_LINE__*/ __BODY__: undefined // Put the goods here. } /** * Read and interpret the data of a __RECORD__ record. */ export class __TEMPLATE_CLASS_NAME__< Value extends __VALUE_TYPE__ = __VALUE_TYPE__ > extends Generated__TEMPLATE_CLASS_NAME__<Value> { /*__USER_EDITABLE_SECTION__*/ }