zig-best-practices

Zig Best Practices

Follows type-first, functional, and error handling patterns from CLAUDE.md. This skill covers Zig-specific idioms only.

Type System Patterns

Tagged unions for mutually exclusive states — prevents invalid combinations that a struct with multiple nullable fields would allow:

const RequestState = union(enum) {
    idle,
    loading,
    success: []const u8,
    failure: anyerror,
};

Explicit error sets — documents exactly what can fail; anyerror hides failure modes:

const ParseError = error{ InvalidSyntax, UnexpectedToken, EndOfInput };
fn parse(input: []const u8) ParseError!Ast { ... }

Distinct types for domain IDs — compiler prevents mixing up different ID types:

const UserId = enum(u64) { _ };
const OrderId = enum(u64) { _ };

Comptime validation — catch invalid configurations at compile time, not runtime:

fn Buffer(comptime size: usize) type {
    if (size == 0) @compileError("buffer size must be greater than 0");
    return struct { data: [size]u8 = undefined, len: usize = 0 };
}

Memory Management

• Pass allocators explicitly to every function that allocates; no global allocator state.
• Place defer resource.deinit() immediately after acquisition — keeps cleanup co-located with creation.
• Use errdefer for cleanup on error paths; defer for unconditional cleanup.
• Use arena allocators for batch/temporary work; they free everything at once.
• Use std.testing.allocator in tests — reports leaks with stack traces.

fn createResource(allocator: std.mem.Allocator) !*Resource {
    const resource = try allocator.create(Resource);
    errdefer allocator.destroy(resource);  // runs only on error
    resource.* = try initializeResource();
    return resource;
}

Key Conventions

• Prefer const over var; prefer slices over raw pointers.
• Prefer comptime T: type over anytype; explicit types produce clearer errors. Use anytype only for genuinely polymorphic cases (callbacks, std.debug.print-style).
• Exhaustive switch: include an else returning an error or unreachable for truly impossible cases.
• Use std.log.scoped(.module_name) for namespaced logging; define a module-level const log constant.
• Larger cohesive files are idiomatic — tests alongside implementation, comptime generics at file scope.