Add linter

.github/workflows/ci.yml

@@ -22,6 +22,12 @@ jobs:
           go-version-file: go.mod
           cache: true
 
+      - name: Lint
+        uses: golangci/golangci-lint-action@v9
+        with:
+          version: v2.12.2
+          args: ./...
+
       - name: Check formatting
         run: |
           unformatted="$(gofmt -l .)"

.golangci.yml

@@ -0,0 +1,164 @@
+version: "2"
+run:
+  tests: true
+linters:
+  enable:
+    - asasalint
+    - asciicheck
+    - bidichk
+    - containedctx
+    - copyloopvar
+    - decorder
+    - depguard
+    - dogsled
+    - durationcheck
+    - embeddedstructfieldcheck
+    - errcheck
+    - errname
+    - errorlint
+    - exptostd
+    - fatcontext
+    - forbidigo
+    - ginkgolinter
+    - gocheckcompilerdirectives
+    - godoclint
+    - gochecknoinits
+    - gochecksumtype
+    - gocritic
+    - gosec
+    - gomoddirectives
+    - gomodguard_v2
+    - goprintffuncname
+    - govet
+    - grouper
+    - iface
+    - importas
+    - inamedparam
+    - ineffassign
+    - intrange
+    - iotamixing
+    - loggercheck
+    - misspell
+    - mirror
+    - modernize
+    - nakedret
+    - noctx
+    - nolintlint
+    - nosprintfhostport
+    - nilnesserr
+    - perfsprint
+    - predeclared
+    - reassign
+    - recvcheck
+    - revive
+    - rowserrcheck
+    - sloglint
+    - staticcheck
+    - testableexamples
+    - testifylint
+    - thelper
+    - unconvert
+    - unparam
+    - unused
+    - usestdlibvars
+    - unqueryvet
+    - usetesting
+    - whitespace
+    - wastedassign
+    - bodyclose
+    - makezero
+    - sqlclosecheck
+  settings:
+    forbidigo:
+      forbid:
+        - pattern: context\.Background()
+          msg: "do not use context.Background() in tests, use t.Context()"
+        - pattern: context\.TODO()
+          msg: "do not use context.TODO() in tests, use t.Context()"
+        - pattern: os\.MkdirTemp()
+          msg: "do not use os.MkdirTemp() in tests, use t.TempDir()"
+        - pattern: os\.Setenv()
+          msg: "do not use os.Setenv() in tests, use t.Setenv()"
+        - pattern: os\.Chdir()
+          msg: "do not use os.Chdir() in tests, use t.Chdir()"
+        - pattern: fmt\.Print.*()
+          msg: "do not use fmt.Print() or fmt.Println() in tests"
+    depguard:
+      rules:
+        old_yaml:
+          files:
+            - "**/*.go"
+          deny:
+            - pkg: gopkg.in/yaml.v3
+              desc: don't use deprecated gopkg.in/yaml.v3, use github.com/goccy/go-yaml instead
+        testify_is_for_tests:
+          files:
+            - "**/*.go"
+            - "!**/*_test.go"
+          deny:
+            - pkg: github.com/stretchr/testify
+              desc: don't use testify in production code
+    gocritic:
+      disabled-checks:
+        - dupImport
+        - hugeParam
+        - rangeValCopy
+        - unnamedResult
+        - appendAssign
+      enabled-tags:
+        - diagnostic
+        - style
+        - performance
+    revive:
+      rules:
+        - name: exported
+          arguments:
+            - checkPrivateReceivers
+        - name: package-comments
+          disabled: false
+    staticcheck:
+      checks:
+        - all
+    gosec:
+      excludes:
+        - G104
+        - G101
+        - G204
+        - G304
+        - G404
+        - G602
+        - G702
+        - G703
+        - G704
+  exclusions:
+    generated: lax
+    presets:
+      - comments
+      - std-error-handling
+    rules:
+      - path-except: _test\.go
+        linters:
+          - forbidigo
+      - path: _test\.go
+        linters:
+          - gosec
+issues:
+  max-same-issues: 3
+formatters:
+  enable:
+    - gci
+    - gofmt
+    - gofumpt
+  settings:
+    gci:
+      custom-order: true
+      sections:
+        - standard
+        - default
+        - prefix(github.com/rumpl/harness)
+    gofmt:
+      rewrite-rules:
+        - pattern: 'interface{}'
+          replacement: 'any'
+    gofumpt:
+      extra-rules: true

claudecode/claudecode.go

@@ -58,11 +58,11 @@ func normalizeModel(model string) string {
 func (p *provider) PrintCommand(prompt string) string {
 	modelFlag := ""
 	if p.model != "" {
-		modelFlag = fmt.Sprintf(" --model %s", harness.ShellEscape(p.model))
+		modelFlag = " --model " + harness.ShellEscape(p.model)
 	}
 	effortFlag := ""
 	if p.effort != "" {
-		effortFlag = fmt.Sprintf(" --effort %s", p.effort)
+		effortFlag = " --effort " + string(p.effort)
 	}
 	return fmt.Sprintf(
 		"claude --print --verbose --dangerously-skip-permissions --include-partial-messages --output-format stream-json%s%s -p %s",

claudecode/claudecode_test.go

@@ -2,6 +2,7 @@ package claudecode
 
 import (
 	"encoding/json"
+	"slices"
 	"strings"
 	"testing"
 
@@ -95,42 +96,42 @@ func TestInteractiveArgs(t *testing.T) {
 		if args[0] != "claude" {
 			t.Errorf("args[0] = %q, want claude", args[0])
 		}
-		if !contains(args, "claude-sonnet-4-6") || !contains(args, "--model") {
+		if !slices.Contains(args, "claude-sonnet-4-6") || !slices.Contains(args, "--model") {
 			t.Errorf("args missing model: %v", args)
 		}
 	})
 
 	t.Run("strips anthropic provider prefix from model", func(t *testing.T) {
 		p := New("anthropic/claude-opus-4-6")
 		args := p.InteractiveArgs("")
-		if !contains(args, "claude-opus-4-6") {
+		if !slices.Contains(args, "claude-opus-4-6") {
 			t.Errorf("args missing normalized model: %v", args)
 		}
-		if contains(args, "anthropic/claude-opus-4-6") {
+		if slices.Contains(args, "anthropic/claude-opus-4-6") {
 			t.Errorf("args should not pass provider/model form to claude: %v", args)
 		}
 	})
 
 	t.Run("includes effort when set", func(t *testing.T) {
 		p := New("claude-opus-4-6", WithEffort(EffortLow))
 		args := p.InteractiveArgs("")
-		if !contains(args, "--effort") || !contains(args, "low") {
+		if !slices.Contains(args, "--effort") || !slices.Contains(args, "low") {
 			t.Errorf("args missing effort: %v", args)
 		}
 	})
 
 	t.Run("omits model when empty", func(t *testing.T) {
 		p := New("")
 		args := p.InteractiveArgs("")
-		if contains(args, "--model") {
+		if slices.Contains(args, "--model") {
 			t.Errorf("args should not contain model: %v", args)
 		}
 	})
 
 	t.Run("omits effort when not set", func(t *testing.T) {
 		p := New("claude-opus-4-6")
 		args := p.InteractiveArgs("")
-		if contains(args, "--effort") {
+		if slices.Contains(args, "--effort") {
 			t.Errorf("args should not contain --effort: %v", args)
 		}
 	})
@@ -367,15 +368,6 @@ func jsonStr(v any) string {
 	return string(b)
 }
 
-func contains(ss []string, s string) bool {
-	for _, v := range ss {
-		if v == s {
-			return true
-		}
-	}
-	return false
-}
-
 func assertEqual(t *testing.T, got, want []harness.Event) {
 	t.Helper()
 	if len(got) != len(want) {

claudecode/parse.go

@@ -7,14 +7,6 @@ import (
 	"github.com/rumpl/harness"
 )
 
-// parseStreamLine handles a single Claude Code stream-json line without
-// retaining cross-line state. Provider.ParseStreamLine uses a stateful parser
-// so it can de-duplicate Claude's partial stream events from the full message
-// snapshots that follow them.
-func parseStreamLine(line string) []harness.Event {
-	return newParser().parseLine(line)
-}
-
 type parser struct {
 	blocks                     map[int]*streamBlock
 	streamedTextSinceAssistant bool
@@ -340,9 +332,5 @@ func join(ss []string) string {
 	if len(ss) == 1 {
 		return ss[0]
 	}
-	out := ""
-	for _, s := range ss {
-		out += s
-	}
-	return out
+	return strings.Join(ss, "")
 }

cmd/harness-example/main.go

@@ -55,7 +55,6 @@ func main() {
 	}
 
 	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
-	defer cancel()
 
 	fmt.Fprintf(os.Stderr, "provider: %s\n", p.Name())
 	fmt.Fprintf(os.Stderr, "prompt:   %s\n\n", prompt)
@@ -87,6 +86,7 @@ func main() {
 			}
 		}
 	})
+	cancel()
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "error: %v\n", err)
 		os.Exit(1)

codex/codex.go

@@ -22,7 +22,7 @@ func (p *provider) Name() string { return "codex" }
 func (p *provider) PrintCommand(prompt string) string {
 	modelFlag := ""
 	if p.model != "" {
-		modelFlag = fmt.Sprintf(" -m %s", harness.ShellEscape(p.model))
+		modelFlag = " -m " + harness.ShellEscape(p.model)
 	}
 	return fmt.Sprintf(
 		"codex exec --json --dangerously-bypass-approvals-and-sandbox%s %s",

codex/codex_test.go

@@ -2,6 +2,7 @@ package codex
 
 import (
 	"encoding/json"
+	"slices"
 	"strings"
 	"testing"
 
@@ -59,15 +60,15 @@ func TestInteractiveArgs(t *testing.T) {
 		if args[0] != "codex" {
 			t.Errorf("args[0] = %q, want codex", args[0])
 		}
-		if !contains(args, "gpt-5.4-mini") || !contains(args, "--model") {
+		if !slices.Contains(args, "gpt-5.4-mini") || !slices.Contains(args, "--model") {
 			t.Errorf("args missing model: %v", args)
 		}
 	})
 
 	t.Run("omits model when empty", func(t *testing.T) {
 		p := New("")
 		args := p.InteractiveArgs("")
-		if contains(args, "--model") {
+		if slices.Contains(args, "--model") {
 			t.Errorf("args should not contain model: %v", args)
 		}
 	})
@@ -233,15 +234,6 @@ func jsonStr(v any) string {
 	return string(b)
 }
 
-func contains(ss []string, s string) bool {
-	for _, v := range ss {
-		if v == s {
-			return true
-		}
-	}
-	return false
-}
-
 func assertEqual(t *testing.T, got, want []harness.Event) {
 	t.Helper()
 	if len(got) != len(want) {

dockeragent/dockeragent_test.go

@@ -2,6 +2,7 @@ package dockeragent
 
 import (
 	"encoding/json"
+	"slices"
 	"strings"
 	"testing"
 
@@ -53,7 +54,7 @@ func TestInteractiveArgs(t *testing.T) {
 	if args[0] != "docker-agent" {
 		t.Errorf("args[0] = %q, want docker-agent", args[0])
 	}
-	if !contains(args, "coder") || !contains(args, "--yolo") {
+	if !slices.Contains(args, "coder") || !slices.Contains(args, "--yolo") {
 		t.Errorf("args missing image or --yolo: %v", args)
 	}
 }
@@ -262,15 +263,6 @@ func jsonStr(v any) string {
 	return string(b)
 }
 
-func contains(ss []string, s string) bool {
-	for _, v := range ss {
-		if v == s {
-			return true
-		}
-	}
-	return false
-}
-
 func assertEqual(t *testing.T, got, want []harness.Event) {
 	t.Helper()
 	if len(got) != len(want) {