go-pcore — Puppet's Pcore type system in pure Go, no cgo

go-pcore is a pure-Go (no cgo) reimplementation of Pcore, the data-type and value model that underpins Puppet, Hiera and Facter values. It gives a Go program the Puppet type calculus — a type model, a type parser (Parse(string) (Type, error)), a value model, and the load-bearing operations: IsInstance (value ∈ type), IsAssignable (subtype), Infer, Generalize, CommonType, and the rich-data ToData / FromData serialization. Type names and semantics track Puppet's Puppet::Pops::Types, so it is a drop-in for Puppet type expressions. It is the foundational type layer for go-puppet and go-ruby-puppet — differential in spirit with the Puppet spec, 100% coverage, CI green across 6 arches.

Type model ready

The Pcore type calculus as Go types: scalar (Integer[min,max], Float, Numeric, String[min,max], Boolean, Undef, Default, Scalar, ScalarData, Data, Any), collection (Array, Hash, Tuple, Struct, Collection) and abstract (Variant, Optional, NotUndef, Enum, Pattern, Regexp, Type, Sensitive), plus Timestamp / Timespan / Binary.

Type parser ready

Parse(string) (Type, error) — a lexer + recursive-descent parser for the Pcore type grammar, matching Puppet’s spelling. Every Type.String() is canonical and round-trips: Parse(t.String()) reproduces t.

Value model ready

Plain Go scalars (bool, int64, float64, string), []Value arrays and *Hash, plus wrappers — Undef, Default, Sensitive (redacts on String() and on serialization), Regexp, Binary, Timestamp, Timespan.

Operations ready

The load-bearing lattice: IsInstance(t, v) (value ∈ type), IsAssignable(a, b) (subtype), Infer(v) (a value’s most specific type), Generalize and CommonType. The assignability arms are covered exhaustively by tests.

Rich-data serialization ready

ToData / FromData implement Pcore’s rich-data protocol (the __ptype / __pvalue tagging): round-trippable through the data-only tree, with Sensitive redacted by design.

Type aliases & TypeSet ready

Named, recursive type aliases and TypeSet (grouped, referenceable type definitions) via a Loader type environment, resolved transparently through Parse / IsInstance / IsAssignable / Infer. Timestamp / Timespan range parameters, SemVer / SemVerRange, Init, Object, Runtime, URI, Iterable / Iterator, Error and Callable are implemented too.

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 Puppet's Pcore type system in pure Go, cgo disabled, so it cross-compiles and embeds anywhere. Every Type.String() is canonical and round-trips through Parse; the assignability lattice is covered exhaustively by tests. It is a standalone, reusable module and the type layer for the sibling org github.com/go-puppet.