Dear sir, you have built a compiler (2022)

Original Article ↗ Hacker News Discussion ↗

What the discussion sees the article as describing

  • Many relate it to the inner-platform effect: rebuilding a general-purpose language or platform inside an app (templating, config, workflow) until it’s essentially a compiler.
  • Some note similar dynamics in web tech: SPAs, canvases, and WebAssembly can become “platforms inside platforms”.

How people accidentally build compilers

  • Common paths:
    • Template engines that gain conditionals, loops, and complex expression syntax.
    • Configuration formats that grow predicates, workflows, and data transformations.
    • “Simple” domain languages (forms, onboarding, workflows) that accumulate logic.
  • Several report real projects where thousands of lines of bespoke logic were thrown away and replaced by simpler templates or plain code.

Is building a compiler / DSL a bad thing?

  • One camp: it’s fine or even good, as long as it’s intentional, scoped, and you understand compiler basics (lexing, parsing, ASTs, semantic checks).
  • Another camp: if you don’t realize early you’re writing a compiler, you almost always end up with an unmaintainable mess.
  • Some recommend writing toy compilers to get intuition before doing this “for real”.

Build vs buy and dependency choices

  • Strong disagreement:
    • Some see homegrown systems as the worst disasters; prefer robust, battle-tested libraries.
    • Others say third‑party deps, toolchains, and transitive bloat have been their biggest pain, and prefer small in‑house solutions.
  • Several frame “when to build on top vs from scratch” as a key senior skill, with no easy metric; both over‑engineering and over‑dependency can backfire.

Config, scripting, and “everything is a compiler”

  • Many observe that rich config languages, YAML + templating (Helm, Kustomize), Kubernetes manifests, Yocto builds, and similar systems are effectively compilers or language workbenches.
  • Alternatives discussed: embed established languages (Lua, JS, Python) instead of inventing new DSLs; or use safer config-as-code systems (e.g., Dhall, Starlark).
  • Some argue every non-trivial config parser is a mini-compiler; the question is how explicit and well‑engineered you make it.