Groups & width-fitting ready
Groups print flat when they fit and break at their breakables when they overflow maxwidth — the exact break_outmost_groups / depth-bucketed GroupQueue algorithm MRI uses, so nested groups break outermost-first.
go-ruby-prettyprint is a pure-Go (no cgo) reimplementation of Ruby's prettyprint — the Wadler/Lindig pretty-printing engine that lays out a stream of text, breakable separators and groups into a width-constrained, nicely indented document. It is a byte-identical port of MRI's prettyprint.rb: each group prints on one line when it fits within maxwidth and is otherwise broken at its breakable points, nesting preserved — without any Ruby runtime. This is the layout engine only — groups, breakables, nesting and the depth-bucketed group queue; the pp object inspector that uses it stays host-side in rbgo. It is the layout backend for go-embedded-ruby, bound by rbgo as a native module just like go-ruby-yaml and go-ruby-marshal — differential-tested against MRI, 100% coverage, CI green across 6 arches and 3 OSes.
Breakables ready
breakable(sep, width) line-break hints that emit their separator when the line is not broken, with the width argument for multibyte or proportional separators.
Nesting & indentation ready
nest(indent) and the group(indent, …) indent argument, with a pluggable genspace block for the indentation string (default DefaultGenSpace — n ASCII spaces).
Open/close text & fill mode ready
group(indent, open, close) wrapping the block in bracketing text counted toward the fit decision, and fill_breakable, where each break is decided individually.
Single-line formatter ready
singleline_format, where breakables become their separator text and nothing ever breaks — plus custom newline and custom maxwidth, matching MRI’s PrettyPrint.new / PrettyPrint.format signatures.
Differential oracle & coverage ready
A shared corpus run through both this package and a generated PrettyPrint.format / singleline_format script, output asserted identical; deterministic ruby-free golden + white-box tests alone hold 100% coverage, gofmt + go vet clean, green across all six 64-bit Go arches and three OSes.
- ready capability complete (exit criteria met, nothing material left)
- active in progress (substantial work shipped, not yet finished)
- planned not started yet (or downstream by design)
A faithful port of Ruby's PrettyPrint layout engine in pure Go, cgo disabled, so it cross-compiles and embeds anywhere. It implements the deterministic Wadler/Lindig algorithm — the buffer, the group stack and the depth-bucketed group queue — so groups print flat when they fit and break outermost-first when they overflow, with nesting and fill mode. Validated differentially against the system ruby binary. It is the layout engine only; the pp object walker that emits text/group/breakable calls stays host-side. A standalone, reusable module bound into the sibling org github.com/go-embedded-ruby.