zig/src-self-hosted/arg.zig

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const std = @import("std");
const debug = std.debug;
const mem = std.mem;
const Allocator = mem.Allocator;
const ArrayList = std.ArrayList;
const HashMap = std.HashMap;
fn trimStart(slice: []const u8, ch: u8) []const u8 {
var i: usize = 0;
for (slice) |b| {
if (b != '-') break;
i += 1;
}
return slice[i..];
}
fn argInAllowedSet(maybe_set: ?[]const []const u8, arg: []const u8) bool {
if (maybe_set) |set| {
for (set) |possible| {
if (mem.eql(u8, arg, possible)) {
return true;
}
}
return false;
} else {
return true;
}
}
// Modifies the current argument index during iteration
fn readFlagArguments(allocator: *Allocator, args: []const []const u8, required: usize, allowed_set: ?[]const []const u8, index: *usize) !FlagArg {
switch (required) {
0 => return FlagArg{ .None = undefined }, // TODO: Required to force non-tag but value?
1 => {
if (index.* + 1 >= args.len) {
return error.MissingFlagArguments;
}
index.* += 1;
const arg = args[index.*];
if (!argInAllowedSet(allowed_set, arg)) {
return error.ArgumentNotInAllowedSet;
}
return FlagArg{ .Single = arg };
},
else => |needed| {
var extra = ArrayList([]const u8).init(allocator);
errdefer extra.deinit();
var j: usize = 0;
while (j < needed) : (j += 1) {
if (index.* + 1 >= args.len) {
return error.MissingFlagArguments;
}
index.* += 1;
const arg = args[index.*];
if (!argInAllowedSet(allowed_set, arg)) {
return error.ArgumentNotInAllowedSet;
}
try extra.append(arg);
}
return FlagArg{ .Many = extra };
},
}
}
const HashMapFlags = HashMap([]const u8, FlagArg, std.hash.Fnv1a_32.hash, mem.eql_slice_u8);
// A store for querying found flags and positional arguments.
pub const Args = struct {
flags: HashMapFlags,
positionals: ArrayList([]const u8),
pub fn parse(allocator: *Allocator, comptime spec: []const Flag, args: []const []const u8) !Args {
var parsed = Args{
.flags = HashMapFlags.init(allocator),
.positionals = ArrayList([]const u8).init(allocator),
};
var i: usize = 0;
next: while (i < args.len) : (i += 1) {
const arg = args[i];
if (arg.len != 0 and arg[0] == '-') {
// TODO: hashmap, although the linear scan is okay for small argument sets as is
for (spec) |flag| {
if (mem.eql(u8, arg, flag.name)) {
const flag_name_trimmed = trimStart(flag.name, '-');
const flag_args = readFlagArguments(allocator, args, flag.required, flag.allowed_set, &i) catch |err| {
switch (err) {
error.ArgumentNotInAllowedSet => {
std.debug.warn("argument '{}' is invalid for flag '{}'\n", args[i], arg);
std.debug.warn("allowed options are ");
for (??flag.allowed_set) |possible| {
std.debug.warn("'{}' ", possible);
}
std.debug.warn("\n");
},
error.MissingFlagArguments => {
std.debug.warn("missing argument for flag: {}\n", arg);
},
else => {},
}
return err;
};
if (flag.mergable) {
var prev = if (parsed.flags.get(flag_name_trimmed)) |entry| entry.value.Many else ArrayList([]const u8).init(allocator);
// MergeN creation disallows 0 length flag entry (doesn't make sense)
switch (flag_args) {
FlagArg.None => unreachable,
FlagArg.Single => |inner| try prev.append(inner),
FlagArg.Many => |inner| try prev.appendSlice(inner.toSliceConst()),
}
_ = try parsed.flags.put(flag_name_trimmed, FlagArg{ .Many = prev });
} else {
_ = try parsed.flags.put(flag_name_trimmed, flag_args);
}
continue :next;
}
}
// TODO: Better errors with context, global error state and return is sufficient.
std.debug.warn("could not match flag: {}\n", arg);
return error.UnknownFlag;
} else {
try parsed.positionals.append(arg);
}
}
return parsed;
}
pub fn deinit(self: *Args) void {
self.flags.deinit();
self.positionals.deinit();
}
// e.g. --help
pub fn present(self: *Args, name: []const u8) bool {
return self.flags.contains(name);
}
// e.g. --name value
pub fn single(self: *Args, name: []const u8) ?[]const u8 {
if (self.flags.get(name)) |entry| {
switch (entry.value) {
FlagArg.Single => |inner| {
return inner;
},
else => @panic("attempted to retrieve flag with wrong type"),
}
} else {
return null;
}
}
// e.g. --names value1 value2 value3
pub fn many(self: *Args, name: []const u8) ?[]const []const u8 {
if (self.flags.get(name)) |entry| {
switch (entry.value) {
FlagArg.Many => |inner| {
return inner.toSliceConst();
},
else => @panic("attempted to retrieve flag with wrong type"),
}
} else {
return null;
}
}
};
// Arguments for a flag. e.g. arg1, arg2 in `--command arg1 arg2`.
const FlagArg = union(enum) {
None,
Single: []const u8,
Many: ArrayList([]const u8),
};
// Specification for how a flag should be parsed.
pub const Flag = struct {
name: []const u8,
required: usize,
mergable: bool,
allowed_set: ?[]const []const u8,
pub fn Bool(comptime name: []const u8) Flag {
return ArgN(name, 0);
}
pub fn Arg1(comptime name: []const u8) Flag {
return ArgN(name, 1);
}
pub fn ArgN(comptime name: []const u8, comptime n: usize) Flag {
return Flag{
.name = name,
.required = n,
.mergable = false,
.allowed_set = null,
};
}
pub fn ArgMergeN(comptime name: []const u8, comptime n: usize) Flag {
if (n == 0) {
@compileError("n must be greater than 0");
}
return Flag{
.name = name,
.required = n,
.mergable = true,
.allowed_set = null,
};
}
pub fn Option(comptime name: []const u8, comptime set: []const []const u8) Flag {
return Flag{
.name = name,
.required = 1,
.mergable = false,
.allowed_set = set,
};
}
};
test "parse arguments" {
const spec1 = comptime []const Flag{
Flag.Bool("--help"),
Flag.Bool("--init"),
Flag.Arg1("--build-file"),
Flag.Option("--color", []const []const u8{
"on",
"off",
"auto",
}),
Flag.ArgN("--pkg-begin", 2),
Flag.ArgMergeN("--object", 1),
Flag.ArgN("--library", 1),
};
const cliargs = []const []const u8{
"build",
"--help",
"pos1",
"--build-file",
"build.zig",
"--object",
"obj1",
"--object",
"obj2",
"--library",
"lib1",
"--library",
"lib2",
"--color",
"on",
"pos2",
};
var args = try Args.parse(std.debug.global_allocator, spec1, cliargs);
debug.assert(args.present("help"));
debug.assert(!args.present("help2"));
debug.assert(!args.present("init"));
debug.assert(mem.eql(u8, ??args.single("build-file"), "build.zig"));
debug.assert(mem.eql(u8, ??args.single("color"), "on"));
const objects = ??args.many("object");
debug.assert(mem.eql(u8, objects[0], "obj1"));
debug.assert(mem.eql(u8, objects[1], "obj2"));
debug.assert(mem.eql(u8, ??args.single("library"), "lib2"));
const pos = args.positionals.toSliceConst();
debug.assert(mem.eql(u8, pos[0], "build"));
debug.assert(mem.eql(u8, pos[1], "pos1"));
debug.assert(mem.eql(u8, pos[2], "pos2"));
}