nice65

Code formatter for CC65 assembly (WIP).

Requirements:

• Python 3.x
• Lark

Features:

• Makes ugly code less ugly
• Fixes indentation and letter cases (mnemonics, registers)
• Understands weird labels, such as colon-less (C64 style) and unnamed (:, :+++)
• Preserves indentation level of comments
• Supports basic macros
• Skips files with ; nice65: ignore comment
• Tested with C64 Kernal/Basic and my 6502-based SBC ROM code

Improvements to do:

• Complex macros
• Proper formatting of arithmetic expressions

Notes:

• Colon-less label mode (-l) breaks macros due to ambiguity of the syntax. Use this option only with legacy code that contains no macros (such as C64 source code).

Installation

pip install nice65

Example usage

# Reformat and print to STDOUT
nice65 samples/example.s

# Modify file in-place
nice65 samples/example.s -m

# Write result to another file
nice65 samples/example.s -o samples/clean.s
# or
nice65 samples/example.s > samples/clean.s

# Recursively reformat all files in directory with extension ".s"
nice65 ./samples/ -r

# Recursively reformat all files in directory with extension ".asm"
nice65 ./samples/ -r -p '*.asm'

Before:

.macro ldax aa, bb ; do stuff
lda aa
ldx bb ; load bb
.endmacro

four .set 9
var = 1337 + four
four .set 4

.macro push_all
    phA
    phX
    PHy
.endmacro

.data
foo:.byte 1

.code
;  Fill zeropage with zeroes
fill:
   ; save registers
   push_all

@start: ldax #0, #0
@again: sta     $00   ,x      ;Yeah, we can use stz, but I just need some code to test nice65!
   inx
bne @again  ; Repeat

  ; Do unnecessary throwaway stuff to test expressions
  ;
  lda #<($42  +  %10101010- (foo*2))
  cmp foo+2
  jmp :+
: lda $1234

@ridiculously_long_label_just_for_the_sake_of_it:PLX
pla

end:rts

After:

.macro  ldax aa, bb     ; do stuff
        LDA aa
        LDX bb          ; load bb
.endmacro

four    .set 9
var = 1337 + four
four    .set 4

.macro  push_all
        PHA
        PHX
        PHY
.endmacro

.data
foo:    .byte 1

.code
; Fill zeropage with zeroes
fill:
        ; save registers
        push_all

    @start:
        ldax #0, #0
    @again:
        STA $00, X      ; Yeah, we can use stz, but I just need some code to test nice65!
        INX
        BNE @again      ; Repeat

        ; Do unnecessary throwaway stuff to test expressions
        ;
        LDA #<($42 + %10101010 - (foo * 2))
        CMP foo + 2
        JMP :+
    :   LDA $1234

    @ridiculously_long_label_just_for_the_sake_of_it:
        PLX
        PLA

end:    RTS

Using with Vim

:nnoremap <M-r> :%! nice65 -<CR>

Using with NeoVim

If you want to be fancy, here's an example on how to have nice65 configured as code formatter for NeoVim with null-ls:

1. Make sure you have the following neovim plugins installed:

   • maxbane/vim-asm_ca65 - sets filetype for CA65 buffers
   • jose-elias-alvarez/null-ls.nvim - allows to run custom scripts as language servers

2. Add configuration:

   local null_ls = require("null-ls")
   null_ls.setup({
       on_attach = on_attach, -- Remove this line if you don't use on_attach
   })
   null_ls.register({
       method = null_ls.methods.FORMATTING,
       filetypes = { 'asm_ca65' },
       generator = null_ls.formatter({
           command = 'nice65',
           args = {'-'},
           to_stdin = true,
           from_stdout = true,
       }),
   })

3. Trigger the formatting:

   :lua vim.lsp.buf.format()