pim
d63ffd6a3a
Reusable, generics-based CLI extracted from vpp-evpn's cmd/evpnc: a declarative command tree (Node[C]) from which dispatch, '?'-help and TAB-completion are derived, an interactive Shell[C], dynamic slot resolvers (context-dependent via captured args), text-or-JSON output (Emit), and color helpers (Paint/Label/KV). Builds on Linux and OpenBSD (readline termios override). Includes a self-contained example and a design proposal under docs/. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
69 lines
2.2 KiB
Go
69 lines
2.2 KiB
Go
// SPDX-FileCopyrightText: (C) Copyright 2026 Pim van Pelt <pim@ipng.ch>
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// SPDX-License-Identifier: Apache-2.0
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//go:build openbsd
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package cli
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import (
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"os"
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"github.com/chzyer/readline"
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"golang.org/x/sys/unix"
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)
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// applyTermFuncs makes readline drive the terminal through golang.org/x/sys/unix.
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//
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// chzyer/readline's own termios handling (term_bsd.go) issues raw
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// syscall.Syscall6(SYS_IOCTL, ...) calls. OpenBSD forbids direct syscalls from
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// outside libc, so those return ENOSYS: readline's IsTerminal() then reports
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// false and the REPL silently degrades to a dumb line reader -- no prompt, no
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// tab completion. x/sys/unix performs the same ioctls through libc.
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//
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// The raw-mode flag set below is copied verbatim from readline's own MakeRaw
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// (term.go), and that match matters: it deliberately leaves OPOST enabled, so a
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// command's "\n" output is still translated to "\r\n". A full cfmakeraw (e.g.
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// golang.org/x/term.MakeRaw) clears OPOST and staircases multi-line output.
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// Only OpenBSD needs this; every other platform keeps readline's native path.
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func applyTermFuncs(cfg *readline.Config) {
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stdin := int(os.Stdin.Fd())
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stdout := int(os.Stdout.Fd())
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var saved *unix.Termios
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cfg.FuncIsTerminal = func() bool {
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_, err := unix.IoctlGetTermios(stdin, unix.TIOCGETA)
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return err == nil
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}
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cfg.FuncMakeRaw = func() error {
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old, err := unix.IoctlGetTermios(stdin, unix.TIOCGETA)
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if err != nil {
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return err
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}
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saved = old
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raw := *old
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raw.Iflag &^= unix.IGNBRK | unix.BRKINT | unix.PARMRK | unix.ISTRIP | unix.INLCR | unix.IGNCR | unix.ICRNL | unix.IXON
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// OPOST is intentionally left set (see the doc comment above).
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raw.Lflag &^= unix.ECHO | unix.ECHONL | unix.ICANON | unix.ISIG | unix.IEXTEN
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raw.Cflag &^= unix.CSIZE | unix.PARENB
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raw.Cflag |= unix.CS8
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raw.Cc[unix.VMIN] = 1
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raw.Cc[unix.VTIME] = 0
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return unix.IoctlSetTermios(stdin, unix.TIOCSETA, &raw)
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}
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cfg.FuncExitRaw = func() error {
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if saved == nil {
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return nil
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}
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err := unix.IoctlSetTermios(stdin, unix.TIOCSETA, saved)
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saved = nil
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return err
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}
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cfg.FuncGetWidth = func() int {
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ws, err := unix.IoctlGetWinsize(stdout, unix.TIOCGWINSZ)
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if err != nil || ws.Col == 0 {
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return 80 // sane default when the width can't be read
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}
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return int(ws.Col)
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}
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}
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