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F3.2: std.cli minimal subcommand + flag parser over explicit []string

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Extend std/cli.sx with a zero-heap argument parser that the caller drives
over a logical argv ([]string), separate from the F3.1 os_args accessor.

Grammar: <group> <command> [--flag VALUE | --bool]... [--json] [-- rest...]
  - (group, command) dispatched against a caller-provided Command table;
    no match -> error.UnknownCommand.
  - value-taking vs boolean flags fixed by each command's FlagSpec list;
    --json is a reserved global boolean surfaced as parsed.json.
  - `--` or the first bare operand ends flag parsing; the remainder is
    parsed.rest (operand views).

Heap discipline (heap-discipline.md): zero heap, zero copy. group/command/
flag values/rest are all VIEWS into args. Parsed is a by-value stack struct;
flag presence/values live in a fixed [16]FlagValue inline array indexed by
spec position (no per-flag allocation, no context.allocator). The flag-spec
list and command table are caller storage passed as views.

Failure surfacing (no silent skip): unknown command, unknown flag, a
value-flag missing its value, and an absent required flag each raise a
specific CliError variant; a caller-owned Diag records the offending token
(index + view) before each raise, since error tags carry no data.

examples/0717 drives the parser over explicit []string vectors: a valid
group/command/--flag/--bool/--json case (asserting parsed values + that
values are views into argv), subcommand dispatch, `--`/bare-operand
separators, and the five failure variants each asserted via destructure +
Diag. zig build && zig build test && run_examples.sh green (385 passed).
This commit is contained in:
agra
2026-06-04 06:13:09 +03:00
parent 8c96290801
commit 17b437ecfb
5 changed files with 412 additions and 0 deletions
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241
library/modules/std/cli.sx
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@@ -92,3 +92,244 @@ os_args :: (buf: []string) -> []string {
}
}
}
// =====================================================================
// Argument PARSER — subcommand dispatch + `--flag` over an EXPLICIT
// logical argv (F3.2).
//
// `parse(args, commands, diag)` reads a caller-supplied logical argument
// vector `[]string` — NOT the process argv. (Mapping process argv ->
// logical args, e.g. dropping the `sx run prog.sx` prefix, is the
// consumer's job; see the `os_args` note above and F3.1.) The grammar:
//
// <group> <command> [--flag VALUE | --bool]... [--json] [-- rest...]
//
// - args[0] is the GROUP, args[1] the COMMAND. The (group, command)
// pair is matched against the caller's `commands` table; no match is
// `error.UnknownCommand`.
// - `--name VALUE` sets a value-taking flag to a VIEW of the next token;
// `--name` alone records a boolean flag's presence. Which is which is
// fixed by the matched command's `FlagSpec` list.
// - `--json` is a RESERVED global boolean mode flag, always recognized
// (commands do not declare it); it surfaces as `parsed.json`.
// - `--` ends flag parsing; the tokens after it become `parsed.rest`
// (operand VIEWS). The first bare (non `--`-prefixed) token likewise
// ends flag parsing and, with the remainder, becomes `parsed.rest`.
// - Only long `--flags` are recognized; a single-dash token (`-v`, `-`)
// is treated as a bare operand. A value-taking flag accepts any next
// token that is not itself a long flag (so `--n -5` gives value "-5").
//
// FAILURE SURFACING (no silent skip): an unknown command, an unknown
// flag, a value-flag missing its value, or an absent required flag each
// raise a meaningful `CliError` on the error channel — never a silent
// default. Because error tags carry no data, the caller-owned `diag`
// records the offending token (its `args` index + a VIEW of it) before
// the raise, so the caller can report exactly which token failed.
//
// HEAP DISCIPLINE (binding, see heap-discipline.md): zero heap, zero copy.
// - group / command / every flag value / every `rest` operand are VIEWS
// (slices) into the caller's `args` — never copied.
// - `Parsed` is a by-value STACK struct the caller binds (like
// `hash.init()`); flag presence/values live in a FIXED-capacity inline
// array `[16]FlagValue` (at most 16 flags per command), indexed
// positionally by the matched command's spec — no per-flag allocation.
// - The flag-spec list and the command table are caller storage passed
// as VIEWS. Nothing here touches `context.allocator`.
//
// Usage:
//
// flags : []FlagSpec = .[
// FlagSpec.{ name = "out", takes_value = true, required = true },
// FlagSpec.{ name = "verbose", takes_value = false, required = false },
// ];
// cmds : []Command = .[ Command.{ group = "ci", command = "publish", flags = flags } ];
// d : Diag = .{};
// p := try parse(args, cmds, @d);
// // p.group == "ci"; p.command == "publish";
// // p.value_of("out"); p.is_set("verbose"); p.json; p.rest
// =====================================================================
// The parser's failure contract. The first four are INPUT errors a caller
// reacts to; `TooManyFlags` rejects a command that declares more flags than
// the inline `Parsed.values` array holds (16) — never a silent truncation.
CliError :: error { UnknownCommand, UnknownFlag, MissingValue, MissingRequired, TooManyFlags }
// One flag's contract: its long name (without the `--`), whether it takes
// a value, and whether it must be present. Caller-owned; passed as a view.
FlagSpec :: struct {
name: string;
takes_value: bool;
required: bool;
}
// One command's contract: a (group, command) pair and its flag specs (a
// VIEW into caller storage).
Command :: struct {
group: string;
command: string;
flags: []FlagSpec;
}
// A parsed flag slot, positionally matched to a `FlagSpec`. `value` is a
// VIEW into `args`, meaningful only for a value-taking flag that was set.
// Defaults make a whole `Parsed` zero-initializable via `.{}`.
FlagValue :: struct {
set: bool = false;
value: string = "";
}
// The offending token on the error path. The caller owns a stack `Diag`
// and passes it by pointer; the parser writes it before any raise because
// error tags carry no data. `index` is the position in `args`, or -1 when
// the failure names a flag rather than an input token (a missing required
// flag sets `token` to the flag name).
Diag :: struct {
index: s64 = -1;
token: string = "";
}
// The parse result — a by-value stack struct. group / command / flag
// values / rest are all VIEWS into `args`.
Parsed :: struct {
group: string;
command: string;
cmd_index: s64;
json: bool;
rest: []string;
spec: []FlagSpec; // view of the matched command's flag specs
values: [16]FlagValue; // fixed inline storage, indexed by spec position
// Presence of a declared flag (boolean or value-taking). False for an
// undeclared name.
is_set :: (self: *Parsed, name: string) -> bool {
j := 0;
while j < self.spec.len {
if self.spec[j].name == name { return self.values[j].set; }
j += 1;
}
return false;
}
// The VIEW value of a value-taking flag, or "" if absent/undeclared.
// Use `is_set` to distinguish "absent" from "present, empty value".
value_of :: (self: *Parsed, name: string) -> string {
j := 0;
while j < self.spec.len {
if self.spec[j].name == name { return self.values[j].value; }
j += 1;
}
return "";
}
}
// True for a long-option token (`--x`). A single dash or a bare word is
// not a flag. Exactly `--` is the separator, tested before this.
is_long_flag :: (s: string) -> bool {
return s.len >= 2 and s[0] == 45 and s[1] == 45; // 45 = '-'
}
// Parse `args` (the logical argv) against the `commands` table, writing
// the offending token into `diag` on the error path. See the section
// header for grammar, failure contract, and heap discipline.
parse :: (args: []string, commands: []Command, diag: *Diag) -> (Parsed, !CliError) {
// ── Dispatch: match (args[0], args[1]) against the command table ──
if args.len < 2 {
diag.index = if args.len == 0 then -1 else 0;
diag.token = if args.len == 0 then "" else args[0];
raise error.UnknownCommand;
}
group := args[0];
command := args[1];
ci := -1;
k := 0;
while k < commands.len {
if commands[k].group == group and commands[k].command == command { ci = k; break; }
k += 1;
}
if ci < 0 {
diag.index = 1;
diag.token = command;
raise error.UnknownCommand;
}
spec := commands[ci].flags;
if spec.len > 16 {
diag.index = -1;
diag.token = command;
raise error.TooManyFlags;
}
// ── Result skeleton ──
// Clear ALL 16 `values` slots (not just the spec prefix): the whole
// struct must be live before it is returned by value. `rest` is an
// empty slice until a `--`/operand sets it.
result : Parsed = ---;
result.group = group;
result.command = command;
result.cmd_index = ci;
result.json = false;
result.spec = spec;
result.rest = args[args.len ..];
j := 0;
while j < 16 {
result.values[j].set = false;
result.values[j].value = "";
j += 1;
}
// ── Flags ──
i := 2;
while i < args.len {
tok := args[i];
if tok == "--" { // explicit separator: rest follows
result.rest = args[i + 1 ..];
break;
}
if !is_long_flag(tok) { // first bare operand ends flag parsing
result.rest = args[i ..];
break;
}
name := tok[2 ..];
if name == "json" { // reserved global mode flag
result.json = true;
i += 1;
continue;
}
si := -1;
s := 0;
while s < spec.len {
if spec[s].name == name { si = s; break; }
s += 1;
}
if si < 0 {
diag.index = i;
diag.token = tok;
raise error.UnknownFlag;
}
if spec[si].takes_value {
if i + 1 >= args.len or is_long_flag(args[i + 1]) {
diag.index = i;
diag.token = tok;
raise error.MissingValue;
}
result.values[si].set = true;
result.values[si].value = args[i + 1]; // VIEW into args
i += 2;
} else {
result.values[si].set = true;
i += 1;
}
}
// ── Required-flag check ──
r := 0;
while r < spec.len {
if spec[r].required and !result.values[r].set {
diag.index = -1;
diag.token = spec[r].name;
raise error.MissingRequired;
}
r += 1;
}
return result;
}