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mirror of https://github.com/imjasonh/nescript synced 2026-07-08 08:55:38 +00:00
nescript/tests/emulator/screenshots/state_machine.png
Claude 81f3fd7de0
Add jsnes emulator harness and fix four codegen bugs it surfaced
Running the compiled example ROMs through a headless puppeteer +
local jsnes harness exposed four latent bugs that the
header-structure-only integration tests couldn't catch:

- src/asm/mod.rs: the first pass treated ANY instruction with
  `AddressingMode::Label` as a label definition, silently dropping
  every `JMP`/`JSR` to a label. Now only `NOP + Label` is a label
  def; other opcodes emit the opcode byte plus a 2-byte absolute
  fixup resolved in pass two. Without this, every example crashed
  with "invalid opcode at $1xxx" once the CPU fell through into
  the math runtime and hit an unbalanced `RTS`.

- src/ir/lowering.rs (lower_handler): handler-local `VarDecl`s
  (e.g. `var i: u8 = 0` inside a `while`) were pushed onto
  `current_locals` but the handler built its own throwaway
  `locals` list, so those var ids never got RAM addresses and
  every `LoadVar`/`StoreVar` for them silently emitted nothing.
  Seed `current_locals` with the state's declared locals and
  reuse it so `lower_statement`'s appends flow through to the
  `IrFunction`. Fixes the black screen in `arrays_and_functions`.

- src/ir/lowering.rs (global init): struct-literal initializers
  on globals (`var player: Player = Player { x: 120, ... }`) fell
  through to `eval_const`, which returned `None` for a
  non-literal, so no init code was emitted. Now the per-field
  synthetic globals each get their own `init_value`. Fixes the
  black screen in `structs_enums_for`.

- src/codegen/mod.rs: the legacy AST codegen was emitting
  `JSR __fn_poke` / treating `peek` as `LDA #0` for the hardware
  intrinsics. It only "worked" before because the broken
  assembler swallowed the bogus JSR. Handle `poke`/`peek` as
  direct STA/LDA to a compile-time-constant absolute address,
  matching the IR codegen's intrinsic path.

The harness lives in `tests/emulator/`: a tiny HTML page that
wraps the `jsnes` npm package, driven by a puppeteer script that
loads each ROM, runs ~180 frames, snapshots the canvas, and
records a smoke-test verdict (booted without a CPU crash, non-zero
pixels rendered, frames differ over time). `npm install && node
run_examples.mjs` from `tests/emulator/` runs the full sweep.

9/9 example ROMs now load, render, and animate where expected.
All 324 unit + 35 integration tests still pass.

https://claude.ai/code/session_014Z5y3Q9krLcAxYpZQJhZ5V
2026-04-12 18:46:58 +00:00

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