Files
browser/src/cli.zig
Halil Durak 604210fd8b cli: introduce variants
Also refactors parsing by moving value parsing functionality to `parseValue` function.
2026-04-27 16:05:40 +03:00

656 lines
28 KiB
Zig

// Copyright (C) 2023-2026 Lightpanda (Selecy SAS)
//
// Francis Bouvier <francis@lightpanda.io>
// Pierre Tachoire <pierre@lightpanda.io>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
const std = @import("std");
const Allocator = std.mem.Allocator;
const lp = @import("lightpanda");
const log = lp.log;
/// Comptime CLI builder that generates a tagged union parser from a
/// declarative command recipe. Each command becomes a union variant whose
/// payload is a struct with one field per option.
///
/// ## Command descriptor fields
///
/// - `name: []const u8` — canonical command name on the command line.
/// - `options: tuple` — tuple of option descriptors (see below). Use `.{}`
/// for none.
/// - `shared_options: tuple` (optional) — extra options merged into this
/// command. Useful for common flags shared across commands.
/// - `positional: struct` (optional) — a single positional argument with
/// `.name` and `.type`. Type must be an optional pointer-to-u8 slice
/// (e.g. `?[:0]const u8`). Positionals can appear anywhere in argv and
/// must be provided; a missing positional returns `error.MissingArgument`.
///
/// ## Option descriptor fields
///
/// - `name: []const u8` — snake_case field name. Both `--snake_case` and
/// `--kebab-case` are accepted on the command line.
/// - `type` — the Zig type of the parsed value (see supported types below).
/// - `default` (optional) — compile-time default when the flag is absent.
/// Rules vary by type; see the defaults section below.
/// - `multiple: bool` (optional) — when `true`, the field becomes a
/// `std.ArrayList(type)` and each occurrence appends. Not supported for
/// `bool` or packed-struct options.
/// - `validator: fn` (optional) — custom parse function that replaces the
/// built-in type switch. See the validator section below.
///
/// ## Supported types and their defaults
///
/// - `bool` — presence flips the field to the opposite of its `default`
/// (so a flag with `default = true` acts as a disable switch). Defaults
/// to `false` when no `default` is given. `?bool` is not allowed.
/// - Integers (`u8`, `u16`, `u31`, `usize`, etc.) — parsed with
/// `std.fmt.parseInt`. Requires `default` unless wrapped in `?`.
/// - `[]const u8`, `[:0]const u8` (and mutable variants) — string slices
/// duped from argv. Sentinel is preserved. Requires `default` unless `?`.
/// - Enums — parsed via `std.meta.stringToEnum`. Returns
/// `error.UnknownArgument` on a bad value. Requires `default` unless `?`.
/// - Packed structs of `bool` fields — parsed from a comma-separated list
/// (e.g. `--strip-mode js,css`). The literal `"full"` sets every field.
/// Unknown names return `error.UnknownArgument`. Requires `default`.
/// `multiple` is not supported.
/// - Optional types default to `null` when `default` is omitted.
///
/// ## Validators
///
/// A `validator` is a custom parse function that takes over argument
/// consumption for an option. Its signature depends on whether `multiple`
/// is set:
///
/// - Single: `fn (Allocator, *ArgIterator) !T` — returns the parsed value.
/// - Multiple: `fn (Allocator, *ArgIterator, *std.ArrayList(T)) !void` —
/// appends directly into the list.
///
/// When a validator is present, the built-in type switch is skipped entirely.
/// The validator owns advancing the iterator and is free to peek ahead.
///
/// ## Example
///
/// ```zig
/// const StripMode = packed struct(u2) {
/// js: bool = false,
/// css: bool = false,
/// };
///
/// const WaitUntil = enum { load, domcontentloaded, networkidle };
///
/// const CommonOptions = .{
/// .{ .name = "verbose", .type = bool },
/// .{ .name = "log_level", .type = ?log.Level },
/// .{ .name = "timeout", .type = u31, .default = 30 },
/// };
///
/// const Cli = cli.Builder(.{
/// .{
/// .name = "serve",
/// .options = .{
/// .{ .name = "host", .type = []const u8, .default = "127.0.0.1" },
/// .{ .name = "port", .type = u16, .default = 9222 },
/// },
/// .shared_options = CommonOptions,
/// },
/// .{
/// .name = "fetch",
/// .positional = .{ .name = "url", .type = ?[:0]const u8 },
/// .options = .{
/// .{ .name = "dump", .type = ?DumpFormat, .validator = dumpValidator },
/// .{ .name = "strip_mode", .type = StripMode, .default = .{} },
/// .{ .name = "wait_until", .type = ?WaitUntil },
/// .{ .name = "extra_header", .type = []const u8, .multiple = true },
/// },
/// .shared_options = CommonOptions,
/// },
/// .{ .name = "version", .options = .{} },
/// .{ .name = "help", .options = .{} },
/// });
///
/// const _, const cmd = try Cli.parse(arena);
/// switch (cmd) {
/// .serve => |opts| listen(opts.host, opts.port),
/// .fetch => |opts| fetch(opts.url.?, opts.dump),
/// .version => printVersion(),
/// .help => printHelp(),
/// }
/// ```
pub fn Builder(comptime commands: anytype) type {
return struct {
const Self = @This();
/// Enum type for provided commands.
pub const Enum = blk: {
var enum_fields: [commands.len]std.builtin.Type.EnumField = undefined;
for (commands, 0..) |command, i| {
enum_fields[i] = .{ .name = command.name, .value = i };
}
break :blk @Type(.{
.@"enum" = .{
.decls = &.{},
.fields = &enum_fields,
.is_exhaustive = true,
.tag_type = std.math.IntFittingRange(0, commands.len),
},
});
};
/// Creates an array of `StructField` out of given options.
fn optionsToStructFields(comptime options: anytype) [options.len]std.builtin.Type.StructField {
var fields: [options.len]std.builtin.Type.StructField = undefined;
inline for (options, 0..) |option, j| {
// Whether prefer `ArrayList` for the option.
const is_multiple = @hasField(@TypeOf(option), "multiple") and option.multiple;
// Whether option has a default value.
const has_default = @hasField(@TypeOf(option), "default");
const T = if (is_multiple) std.ArrayList(option.type) else option.type;
const default = blk: {
if (is_multiple) {
// We currently don't allow default values for lists.
if (has_default) {
@compileError("`default` is not allowed for lists");
}
// Multiples are always initialized the same.
break :blk @as(*const anyopaque, @ptrCast(&@as(T, .{})));
}
switch (@typeInfo(option.type)) {
.optional => |optional| {
if (optional.child == bool) {
@compileError("?bool is not supported, prefer enum");
}
// If type is an optional type without default value, prefer null.
if (!has_default) {
break :blk @as(*const anyopaque, @ptrCast(&@as(T, null)));
}
// We have default value for an optional.
break :blk @as(*const anyopaque, @ptrCast(&@as(T, option.default)));
},
.bool => {
// Prefer `false` if no default.
const default = if (has_default) option.default else false;
break :blk @as(*const anyopaque, @ptrCast(&@as(T, default)));
},
inline else => {
if (!has_default) {
@compileError("option `" ++ option.name ++ "` is not optional type and has no default value");
}
break :blk @as(*const anyopaque, @ptrCast(&@as(T, option.default)));
},
}
};
fields[j] = .{
.name = option.name,
.type = T,
.default_value_ptr = default,
.is_comptime = false,
.alignment = @alignOf(T),
};
}
return fields;
}
/// Union type for provided commands.
pub const Union = blk: {
var union_fields: [commands.len]std.builtin.Type.UnionField = undefined;
for (commands, 0..) |command, i| {
const Command = @TypeOf(command);
const options = command.options;
const fields = optionsToStructFields(options) ++
(if (@hasField(Command, "shared_options"))
optionsToStructFields(command.shared_options)
else
.{}) ++
(if (@hasField(Command, "positional"))
[1]std.builtin.Type.StructField{
.{
.name = command.positional.name,
.type = command.positional.type,
.default_value_ptr = @ptrCast(&@as(command.positional.type, null)),
.is_comptime = false,
.alignment = @alignOf(command.positional.type),
},
}
else
.{});
const T = @Type(.{
.@"struct" = .{
.decls = &.{},
.fields = &fields,
.is_tuple = false,
.layout = .auto,
},
});
union_fields[i] = .{ .name = command.name, .type = T, .alignment = @alignOf(T) };
}
break :blk @Type(.{
.@"union" = .{
.decls = &.{},
.fields = &union_fields,
.layout = .auto,
.tag_type = Enum,
},
});
};
/// Parses executable name, command and options via single call.
pub fn parse(allocator: Allocator) !struct { []const u8, Union } {
var args = try std.process.argsWithAllocator(allocator);
defer args.deinit();
const exec_name = std.fs.path.basename(args.next().?);
const cmd_str: []const u8 = args.next() orelse "serve";
inline for (commands) |command| {
// Match a command.
if (std.mem.eql(u8, cmd_str, command.name)) {
return .{ exec_name, try parseCommand(allocator, command, &args) };
}
}
// Last resort, try sniffing.
const command_enum = try sniffCommand(cmd_str);
// `help` takes no arguments; short-circuit so the sniffed flag
// isn't re-parsed as an unknown option.
if (command_enum == .help) {
return .{ exec_name, .{ .help = .{} } };
}
// "cmd_str" wasn't a command but an option. We can't reset args, but
// we can create a new one. Not great, but this fallback is temporary
// as we transition to this command mode approach.
args.deinit();
args = try std.process.argsWithAllocator(allocator);
// Skip the `exec_name`.
_ = args.skip();
inline for (commands) |command| {
if (std.mem.eql(u8, @tagName(command_enum), command.name)) {
return .{ exec_name, try parseCommand(allocator, command, &args) };
}
}
unreachable;
}
/// Try to sniff the command out of given option.
/// Only exists for legacy reasons; hence hardcoded.
fn sniffCommand(cmd_str: []const u8) error{UnknownCommand}!Enum {
if (std.mem.startsWith(u8, cmd_str, "--") == false) {
return .fetch;
}
// Fetch heuristics.
inline for (.{
"--dump",
"--strip-mode",
"--strip_mode",
"--with-base",
"--with_base",
"--with-frames",
"--with_frames",
}) |heuristic| {
if (std.mem.eql(u8, cmd_str, heuristic)) {
return .fetch;
}
}
// Serve heuristics.
inline for (.{
"--host",
"--port",
"--timeout",
}) |heuristic| {
if (std.mem.eql(u8, cmd_str, heuristic)) {
return .serve;
}
}
// Legacy `--help` flag maps to the `help` command.
if (std.mem.eql(u8, cmd_str, "--help")) {
return .help;
}
return error.UnknownCommand;
}
/// Returns the type for validator function.
pub fn ValidatorFn(comptime T: type, comptime is_multiple: bool) type {
if (is_multiple) {
return *const fn (Allocator, *std.process.ArgIterator, *std.ArrayList(T)) anyerror!void;
}
return *const fn (Allocator, *std.process.ArgIterator) anyerror!T;
}
/// Turns a snake_case string to kebab-case in comptime.
fn toKebabCase(comptime str: []const u8) [str.len]u8 {
var output: [str.len]u8 = str[0..str.len].*;
for (&output) |*c| if (c.* == '_') {
c.* = '-';
};
return output;
}
fn parseValue(
allocator: Allocator,
args: *std.process.ArgIterator,
/// Pointer to field; *T.
target: anytype,
/// `Option` doesn't have a concrete type; this field expects:
/// ```zig
/// Option{
/// .name = "option_name",
/// .type = T,
/// .multiple = ?bool,
/// .validator = ?ValidatorFn(T, is_multiple),
/// };
/// ```
option: anytype,
) !void {
const kebab_cased = "--" ++ comptime toKebabCase(option.name);
const OptionType = @TypeOf(option);
const is_multiple = @hasField(OptionType, "multiple") and option.multiple;
const has_validator = @hasField(OptionType, "validator");
// Prefer validator for parsing if provided.
if (has_validator) {
const validator = option.validator;
if (is_multiple) {
// Pass the list.
try @call(.auto, validator, .{ allocator, args, target });
} else {
// Receive the value from return.
const v = try @call(.auto, validator, .{ allocator, args });
target.* = v;
}
return;
}
// Extract type info.
const T = option.type;
const option_info = blk: {
const info = @typeInfo(T);
// If wrapped in optional, prefer the child type.
if (info == .optional) break :blk @typeInfo(info.optional.child);
break :blk info;
};
// Parse by type.
return switch (option_info) {
.int => |int| {
const Int = std.meta.Int(int.signedness, int.bits);
const str = args.next() orelse return error.MissingArgument;
const v = std.fmt.parseInt(Int, str, 10) catch |err| {
switch (err) {
error.Overflow => log.fatal(.app, "range overflow", .{ .arg = kebab_cased, .value = str }),
error.InvalidCharacter => log.fatal(.app, "invalid character", .{ .arg = kebab_cased, .value = str }),
}
return error.InvalidArgument;
};
if (is_multiple) {
// Push to ArrayList.
try target.append(allocator, v);
} else {
target.* = v;
}
},
.pointer => |pointer| {
const not_u8_slice = pointer.child != u8 or pointer.size != .slice;
if (not_u8_slice) {
@compileError("Only []u8, []const u8, [:sentinel]u8 and [:sentinel]const u8 pointers are supported");
}
const v = blk: {
const str = args.next() orelse return error.MissingArgument;
// DupeZ branch.
if (comptime pointer.sentinel()) |sentinel| {
const buf = try allocator.alignedAlloc(u8, .fromByteUnits(pointer.alignment), str.len + 1);
@memcpy(buf[0..str.len], str);
buf[str.len] = sentinel;
break :blk buf[0..str.len :sentinel];
}
// Dupe branch.
const buf = try allocator.alignedAlloc(u8, .fromByteUnits(pointer.alignment), str.len);
@memcpy(buf, str);
break :blk buf;
};
if (is_multiple) {
try target.append(allocator, v);
} else {
target.* = v;
}
},
.@"struct" => |_struct| {
// Don't support multiple for structs for now.
if (is_multiple) {
@compileError("multiple option is not supported for structs");
}
const not_packed = _struct.layout != .@"packed";
if (not_packed) {
@compileError("only packed structs are allowed");
}
const str = args.next() orelse return error.MissingArgument;
if (std.mem.eql(u8, str, "full")) {
// "full" sets all the fields of packed struct.
const Int = _struct.backing_integer orelse @compileError("packed struct must provide a backing integer");
target.* = @bitCast(@as(Int, std.math.maxInt(Int)));
} else {
// Parse given args.
var it = std.mem.tokenizeScalar(u8, str, ',');
outer: while (it.next()) |part| {
const trimmed = std.mem.trim(u8, part, &std.ascii.whitespace);
inline for (_struct.fields) |f| {
lp.assert(f.type == bool, "all fields of packed struct must be boolean", .{
.option = option.name,
.field = f.name,
});
if (std.mem.eql(u8, trimmed, @as([]const u8, f.name))) {
@field(target, f.name) = true;
continue :outer;
}
}
// Invalid option choice.
log.fatal(.app, "invalid option choice", .{ .arg = kebab_cased, .value = trimmed });
return error.InvalidArgument;
}
}
},
.@"enum" => {
const E = switch (@typeInfo(T)) {
.optional => |optional| optional.child,
inline else => T,
};
const str = args.next() orelse return error.MissingArgument;
const v = std.meta.stringToEnum(E, str) orelse {
log.fatal(.app, "invalid option choice", .{ .arg = kebab_cased, .value = str });
return error.InvalidArgument;
};
if (is_multiple) {
try target.append(allocator, v);
} else {
target.* = v;
}
},
.bool => {
if (is_multiple) {
@compileError("multiple option is not supported for booleans");
}
const default = blk: {
if (@hasField(@TypeOf(option), "default")) {
break :blk option.default;
}
break :blk false;
};
// Set opposite of the default.
target.* = !default;
},
else => unreachable,
};
}
/// Parses the command with its options.
fn parseCommand(
allocator: Allocator,
command: anytype,
args: *std.process.ArgIterator,
) !Union {
const Command = @FieldType(Union, command.name);
var c = Command{};
const options = blk: {
if (@hasField(@TypeOf(command), "shared_options")) {
break :blk command.options ++ command.shared_options;
}
break :blk command.options;
};
iter_args: while (args.next()) |option_name| {
inline for (options) |option| {
// We allow both `--my-option` and `--my_option` variants;
// assuming given `option` struct prefer snake_case for `name`.
// Match an option.
if (std.mem.eql(u8, option_name, "--" ++ option.name) or
std.mem.eql(u8, option_name, "--" ++ comptime toKebabCase(option.name)))
{
try parseValue(allocator, args, &@field(c, option.name), option);
continue :iter_args;
}
const is_multiple = @hasField(@TypeOf(option), "multiple") and option.multiple;
// Parse for variants if there are.
const has_variants = @hasField(@TypeOf(option), "variants");
if (has_variants) {
inline for (option.variants) |variant| {
if (std.mem.eql(u8, option_name, "--" ++ variant.name) or
std.mem.eql(u8, option_name, "--" ++ comptime toKebabCase(variant.name)))
{
const opts = blk: {
if (@hasField(@TypeOf(variant), "validator")) {
break :blk .{
.name = variant.name,
.type = option.type,
.multiple = is_multiple,
.validator = variant.validator,
};
}
break :blk .{ .name = variant.name, .type = option.type, .multiple = is_multiple };
};
try parseValue(allocator, args, &@field(c, option.name), opts);
continue :iter_args;
}
}
}
}
// Encountered an option we don't know of.
if (std.mem.startsWith(u8, option_name, "--")) {
log.fatal(.app, "unknown argument", .{ .mode = command.name, .arg = option_name });
return error.UnknownOption;
}
// Parse positional arg if provided; can be given out of order:
//
// lightpanda fetch --wait-ms 2_000 "https://lightpanda.io" --dump "html"
// ---------------------------------^
if (comptime @hasField(@TypeOf(command), "positional")) {
const positional = command.positional;
// Already given one.
if (@field(c, positional.name) != null) {
return error.TooManyPositionalArguments;
}
// The positional must be an optional type.
const info = @typeInfo(@typeInfo(positional.type).optional.child);
const str = @as([]const u8, option_name);
switch (info) {
.pointer => |pointer| {
const not_u8_slice = pointer.child != u8 or pointer.size != .slice;
if (not_u8_slice) {
@compileError("Only []u8, []const u8, [:sentinel]u8 and [:sentinel]const u8 pointers are supported");
}
const v = blk: {
// DupeZ branch.
if (comptime pointer.sentinel()) |sentinel| {
const buf = try allocator.alignedAlloc(u8, .fromByteUnits(pointer.alignment), str.len + 1);
@memcpy(buf[0..str.len], str);
buf[str.len] = sentinel;
break :blk buf[0..str.len :sentinel];
}
// Dupe branch.
const buf = try allocator.alignedAlloc(u8, .fromByteUnits(pointer.alignment), str.len);
@memcpy(buf, str);
break :blk buf;
};
@field(c, positional.name) = v;
},
inline else => @compileError("not supported"),
}
} else {
log.fatal(.app, "unknown argument", .{ .mode = command.name, .arg = option_name });
return error.UnknownOption;
}
}
// A non-optional positional that is still null after parsing is missing.
if (comptime @hasField(@TypeOf(command), "positional")) {
const is_optional = @typeInfo(command.positional.type) == .optional;
if (!is_optional and @field(c, command.positional.name) == null) {
return error.MissingArgument;
}
}
return @unionInit(Union, command.name, c);
}
};
}