dialect

Documentation

Overview

Package dialect holds one package per shell the substrate imitates.

Nothing here is imported by syntax or interp, and that is the point. The substrate defines the *questions* — a grammar flag, a semantics axis, a diagnostic value — and each shell answers them in its own package. Adding a shell adds a directory; it does not touch the core.

Each package exports the same four functions, one per vector:

Dialect()     what parses
Semantics()   what it means where the shells conflict
Diagnostics() how failure is reported
Style()       how a formatter lays it back out

Style is the newest and the thinnest, because most of what a formatter decides is not a shell's to decide. It earns its place on one question: zsh's brace-spelled bodies parse to the tree the keyword spelling parses to, so nothing but a dialect's stated preference can say which spelling a formatter writes back. docs/spec/style.md holds the measurements.

No shell is defined in terms of another. Every preset starts from syntax.POSIX or interp.PosixSemantics — the standard, which is not a shell and has no successors — and overrides only what was measured to differ. Deriving zsh from bash, which is what this replaced, once silently gave zsh bash's answer for whether a readonly reassignment is fatal; zsh's own answer is the opposite, and nothing caught it until something exercised it. A preset that inherits from a sibling inherits its future mistakes too.