Go Standards

Severity System

• •MUST -- Enforced by CI/review. Violations block merge.
• •SHOULD -- Strong recommendations. Deviations require rationale in PR.
• •CAN -- Allowed without extra approval. Use when beneficial.

1 -- Before Coding

• •BP-1 (MUST) Ask clarifying questions for ambiguous requirements.
• •BP-2 (MUST) Draft and confirm an approach (API shape, data flow, failure modes) before writing code.
• •BP-3 (SHOULD) When >2 approaches exist, list pros/cons and rationale.
• •BP-4 (SHOULD) Define testing strategy (unit/integration) and observability signals up front.

2 -- Modules and Dependencies

• •MD-1 (SHOULD) Prefer stdlib; introduce deps only with clear payoff; track transitive size and licenses.
• •MD-2 (CAN) Use govulncheck for dependency auditing and updates.

3 -- Code Style

• •CS-1 (MUST) Enforce gofmt and go vet on all code.
• •CS-2 (MUST) Avoid stutter in names: package kv; type Store not KVStore in kv.
• •CS-3 (SHOULD) Small interfaces near consumers; prefer composition over inheritance.
• •CS-4 (SHOULD) Avoid reflection on hot paths; prefer generics when it clarifies and speeds.
• •CS-5 (MUST) Use input structs for functions receiving more than 2 arguments. Context is always a separate first parameter, never in the input struct.
• •CS-6 (SHOULD) Declare function input structs immediately before the function that consumes them.
• •CS-7 (MUST) Use any instead of interface{}.
• •CS-8 (SHOULD) Avoid else; use early return, continue, or break.
• •CS-9 (MUST) Import grouping order: stdlib, third-party, org, local. Separate with blank lines.
• •CS-10 (SHOULD) Reduce nesting with early returns. Handle the error case first, then continue with the happy path.
• •CS-11 (SHOULD) Reduce scope of variables; declare closest to first use.
• •CS-12 (SHOULD) Use raw string literals to avoid escaping.
• •CS-13 (MUST) Use field names in struct initialization (no positional).
• •CS-14 (SHOULD) Group similar declarations together.
• •CS-15 (SHOULD) Prefer strconv over fmt for string/number conversions.
• •CS-16 (SHOULD) Nil is a valid slice; don't return empty slices just to avoid nil.
• •CS-17 (SHOULD) Use "time" package types properly; never use raw int for durations.
• •CS-18 (SHOULD) Use field tags in marshaled structs (JSON, TOML, etc.).

// CS-5: Input struct for 3+ arguments (context stays outside)
type WalkInput struct {
    Root       string
    MaxDepth   int
    IgnoreFile string
}

func Walk(ctx context.Context, in WalkInput) ([]FileDescriptor, error) {
    // ...
}

// CS-9: Import ordering
import (
    "context"
    "fmt"
    "os"

    "github.com/spf13/cobra"
    "golang.org/x/sync/errgroup"

    "github.com/raven/raven/internal/config"
    "github.com/raven/raven/internal/discovery"
)

// CS-8: Early return instead of else
func process(fd FileDescriptor) error {
    if fd.IsBinary {
        return ErrSkipped
    }
    // happy path continues at top level
    return nil
}

4 -- Errors

• •ERR-1 (MUST) Wrap with %w and context: fmt.Errorf("open %s: %w", path, err).
• •ERR-2 (MUST) Use errors.Is/errors.As for control flow; never match error strings.
• •ERR-3 (SHOULD) Define sentinel errors in the package; document their behavior.
• •ERR-4 (CAN) Use context.WithCancelCause and context.Cause for propagating error causes.
• •ERR-5 (MUST) Handle errors once: log OR return, never both.
• •ERR-6 (MUST) Do not panic; return errors instead. Panics are reserved for truly unrecoverable programmer bugs.
• •ERR-7 (SHOULD) Prefer errors.New for simple static errors; custom types for errors needing fields.
• •ERR-8 (SHOULD) Use %w when callers need Is/As; use %v to intentionally break the error chain.
• •ERR-9 (MUST) Handle type assertion failures with comma-ok pattern.

// ERR-1 + ERR-3: Sentinel errors and wrapping
var (
    ErrSkipped   = errors.New("file skipped")
    ErrBudgetExc = errors.New("token budget exceeded")
)

func processFile(path string) error {
    data, err := os.ReadFile(path)
    if err != nil {
        return fmt.Errorf("read %s: %w", path, err)
    }
    // ...
    return nil
}

// ERR-9: Type assertion with comma-ok
val, ok := msg.(tea.KeyMsg)
if !ok {
    return m, nil
}

5 -- Concurrency

• •CC-1 (MUST) The sender closes channels; receivers never close.
• •CC-2 (MUST) Tie goroutine lifetime to a context.Context; prevent leaks.
• •CC-3 (MUST) Protect shared state with sync.Mutex/atomic; no "probably safe" races.
• •CC-4 (SHOULD) Use errgroup for fan-out work; cancel on first error.
• •CC-5 (CAN) Prefer buffered channels only with documented rationale (throughput/back-pressure).
• •CC-6 (MUST) Never fire-and-forget goroutines. Every goroutine must be tracked and joined.

// CC-2 + CC-4: errgroup with context cancellation
func walkParallel(ctx context.Context, paths []string) ([]FileDescriptor, error) {
    g, ctx := errgroup.WithContext(ctx)
    g.SetLimit(runtime.NumCPU())

    var mu sync.Mutex
    var results []FileDescriptor

    for _, p := range paths {
        g.Go(func() error {
            fd, err := processPath(ctx, p)
            if err != nil {
                return fmt.Errorf("process %s: %w", p, err)
            }
            mu.Lock()
            results = append(results, fd)
            mu.Unlock()
            return nil
        })
    }

    if err := g.Wait(); err != nil {
        return nil, err
    }
    return results, nil
}

6 -- Contexts

• •CTX-1 (MUST) ctx context.Context is always the first parameter; never store ctx in structs.
• •CTX-2 (MUST) Propagate non-nil ctx; honor Done, deadlines, and timeouts.
• •CTX-3 (CAN) Expose WithX(ctx) helpers that derive deadlines from config.

// CTX-1: Context is always first, before the input struct
func (s *Scanner) Scan(ctx context.Context, in ScanInput) ([]Finding, error) {
    select {
    case <-ctx.Done():
        return nil, ctx.Err()
    default:
    }
    // proceed with scan...
}

7 -- Testing

• •T-1 (MUST) Table-driven tests; deterministic and hermetic by default.
• •T-2 (MUST) Run -race in CI; add t.Cleanup for teardown.
• •T-3 (SHOULD) Mark safe tests with t.Parallel().
• •T-4 (SHOULD) Split success and error test paths into separate test functions.
• •T-5 (SHOULD) Use testify: require for fatal assertions, assert for soft checks.
• •T-6 (MUST) Document only public interfaces, types, functions, methods.

// T-1 + T-5: Table-driven test with testify
func TestTokenizer_Count(t *testing.T) {
    tests := []struct {
        name    string
        content string
        want    int
    }{
        {name: "empty", content: "", want: 0},
        {name: "single word", content: "hello", want: 1},
        {name: "go function", content: "func main() {}", want: 5},
    }
    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            t.Parallel()
            got, err := tokenizer.Count(tt.content)
            require.NoError(t, err)
            assert.Equal(t, tt.want, got)
        })
    }
}

8 -- Logging and Observability

• •OBS-1 (MUST) Structured logging with slog; use levels and consistent field names.
• •OBS-2 (SHOULD) Correlate logs, metrics, and traces via request IDs from context.

slog.Info("pipeline stage complete",
    "stage", "discovery",
    "files", len(results),
    "duration", elapsed,
)

9 -- Performance

• •PERF-1 (MUST) Measure before optimizing: pprof, go test -bench, benchstat.
• •PERF-2 (SHOULD) Avoid allocations on hot paths; reuse buffers; prefer bytes/strings APIs.
• •PERF-3 (CAN) Add microbenchmarks for critical functions and track regressions in CI.
• •PERF-4 (SHOULD) Specify container capacity; pre-allocate slices and maps when size is known.

// PERF-4: Pre-allocate with known capacity
files := make([]FileDescriptor, 0, len(paths))
tierMap := make(map[string]int, len(files))

10 -- Configuration

• •CFG-1 (MUST) Config via env/flags; validate on startup; fail fast on invalid config.
• •CFG-2 (MUST) Treat config as immutable after init; pass explicitly, not via globals.
• •CFG-3 (SHOULD) Provide sane defaults and clear documentation.

11 -- APIs and Boundaries

• •API-1 (MUST) Document exported items: // Foo does ...; keep exported surface minimal.
• •API-2 (MUST) Accept interfaces where variation is needed; return concrete types unless abstraction is required.
• •API-3 (SHOULD) Keep functions small, orthogonal, and composable.
• •API-4 (SHOULD) Avoid embedding types in public structs (leaks implementation).
• •API-5 (CAN) Use functional options pattern for extensibility.
• •API-6 (MUST) Verify interface compliance at compile time.
• •API-7 (SHOULD) Avoid mutable globals. If unavoidable, protect with mutex.
• •API-8 (SHOULD) Avoid init(). Prefer explicit initialization.
• •API-9 (MUST) Exit only in main(). All other code returns errors.

// API-6: Compile-time interface compliance
var _ discovery.Walker = (*FileWalker)(nil)

// API-5: Functional options
type Option func(*Server)

func WithLogger(l *slog.Logger) Option {
    return func(s *Server) { s.logger = l }
}

func WithTimeout(d time.Duration) Option {
    return func(s *Server) { s.timeout = d }
}

func NewServer(addr string, opts ...Option) *Server {
    s := &Server{addr: addr, timeout: 30 * time.Second}
    for _, opt := range opts {
        opt(s)
    }
    return s
}

12 -- Security

• •SEC-1 (MUST) Validate inputs; set explicit I/O timeouts; prefer TLS everywhere.
• •SEC-2 (MUST) Never log secrets; manage secrets outside code (env/secret manager).
• •SEC-3 (SHOULD) Limit filesystem/network access by default; principle of least privilege.
• •SEC-4 (CAN) Add fuzz tests for untrusted inputs (redaction patterns, config parsing).

13 -- CI/CD

• •CI-1 (MUST) Lint, vet, test (-race), and build on every PR; cache modules/builds.
• •CI-2 (MUST) Reproducible builds with -trimpath; embed version via -ldflags "-X main.version=$TAG".

14 -- Tooling Gates

• •G-1 (MUST) go vet ./... passes.
• •G-2 (MUST) golangci-lint run passes with project config.
• •G-3 (MUST) go test -race ./... passes.

15 -- Defensive Coding

• •DC-1 (MUST) Copy slices and maps at package boundaries; do not hold references to caller data.
• •DC-2 (SHOULD) Zero-value mutexes are valid; never use pointer to mutex.
• •DC-3 (SHOULD) Defer to clean up resources (files, locks, connections).
• •DC-4 (SHOULD) Channel size is one or none; document rationale for larger buffers.
• •DC-5 (SHOULD) Start enums at one; reserve zero value for "unset".

// DC-1: Copy slices at boundaries
func (c *Config) SetIgnorePatterns(patterns []string) {
    c.patterns = make([]string, len(patterns))
    copy(c.patterns, patterns)
}

// DC-5: Enums start at one
type Tier int

const (
    TierUnset Tier = iota // 0 = unset/invalid
    TierCritical          // 1
    TierImportant         // 2
    TierNormal            // 3
)