0xferrous
Foundry trace folding in eth.nvim.
Posted on :: 195 Words :: Tags: neovim , plugin , development , lua , ethereum , blockchain , web3

A new feature added to eth.nvim that allows folding foundry traces' output

Problem

Some traces are too huge to be comfortable navigating in the terminal even with a pager. Folding irrelevant subcall traces can make it more manageable.

Solution

Ideal solution would be a interactive traces explorer built right into foundry, but we are going to leave that feature contribution for another day. For now I solved the problem using neovim's foldexpr.

Commands added

  • :EthTraceFoldEnable to enable folding
  • :EthTraceFoldDisable to disable folding
  • :EthTraceFoldToggle to toggle folding

How It Works

  • Fold level derives from each line’s left prefix after stripping ANSI:
    • Ignore leading whitespace.
    • Count │ as nesting depth.
    • If the prefix contains ├ or └, add +1 (branch line).
    • Lines without these prefixes get depth 0.
  • The plugin sets buffer-local:
    • foldmethod=expr
    • foldexpr=v:lua.require'eth-nvim.trace'.foldexpr(v:lnum)
    • foldtext=v:lua.require'eth-nvim.trace'.foldtext()
  • ANSI-safe: strip_ansi removes SGR/CSI sequences so colored traces still fold correctly.

Quick Start

  • Enable in the current buffer: :EthTraceFoldEnable
  • Toggle: :EthTraceFoldToggle
  • Use zM/zR to close/open all folds and za to toggle a fold under the cursor.
  • Programmatic control:
    • require('eth-nvim').enable_trace_folds()
    • require('eth-nvim').disable_trace_folds()
    • require('eth-nvim').toggle_trace_folds()

Example Depths:

  │ ├─ call A → depth 2
  │ │ └─ return → depth 3
  └─ final → depth 1