[Repo Assist] refactor: extract SortedSetKeys and atomicWriteFile to eliminate code duplication (#8042)

🤖 *This is an automated PR from Repo Assist.*

Addresses duplicate code patterns identified in #8021, specifically
sub-issues #8022 and #8023.

## What Changed

### 1. `strutil.SortedSetKeys` — new utility (closes #8022)

Added `SortedSetKeys(set map[string]struct{}) []string` to
`internal/strutil/strutil.go`. This eliminates the identical 5-line
map-to-sorted-slice block that appeared in three places:

- `internal/urlutil/domains.go` (×2: `ExtractURLDomainsFromValue`,
`ExtractURLDomains`)
- `internal/logger/observed_url_domains_logger.go` (×1: `writeToFile`)

### 2. `atomicWriteFile` — shared logger helper + bug fix (closes #8023)

Added `atomicWriteFile(filePath string, data []byte, perm os.FileMode)
error` to `internal/logger/common.go`. This helper:

- Writes data atomically via temp-file + rename
- Includes the `os.IsNotExist` guard on cleanup that was **already
present** in `observed_url_domains_logger.go` but **missing** in
`tools_logger.go` (latent bug fixed)
- Logs a WARNING on unexpected cleanup failures

Both `ToolsLogger.writeToFile` and
`ObservedURLDomainsLogger.writeToFile` now delegate to this helper.

## Root Cause

The `writeToFile` methods in `tools_logger.go` and
`observed_url_domains_logger.go` were written independently and diverged
in error handling. The `os.Remove` call in `tools_logger.go` silently
discarded cleanup errors, while `observed_url_domains_logger.go`
correctly guarded against `os.IsNotExist`. `atomicWriteFile` adopts the
correct variant for both callers.

## Impact

| Metric | Before | After |
|--------|--------|-------|
| Duplicated map→slice blocks | 3 | 0 |
| Duplicated atomic-write blocks | 2 | 0 |
| Lines removed (net) | — | −18 |
| Latent bug (missing IsNotExist guard) | present | fixed |

## Test Status

⚠️ Build infrastructure (`proxy.golang.org`) is blocked in this
environment. All 6 changed files pass `gofmt -e` with no parse errors.
CI will run the full test suite including `TestWriteToFile_RenameFails`
which exercises the cleanup path.

**Existing tests that cover the changed paths:**
- `TestWriteToFile_RenameFails` — verifies temp file is cleaned up on
rename failure
- `TestWriteToFile_WriteFileFails` — verifies error propagation when
write fails
- `TestWriteToFile_Success` — verifies normal write path
- `TestSortedSetKeys` (new) — 4 subtests covering sorted output,
empty/nil maps, single element




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Author: lpcox

internal/logger/common.go

@@ -393,6 +393,23 @@ func initLogFile(logDir, fileName string, flags int) (*os.File, error) {
 	return file, nil
 }
 
+// atomicWriteFile writes data to filePath atomically using a temp-file + rename strategy.
+// On rename failure the temp file is removed; a removal error that is not os.IsNotExist
+// is logged as a warning but does not mask the primary rename error.
+func atomicWriteFile(filePath string, data []byte, perm os.FileMode) error {
+	tempPath := filePath + ".tmp"
+	if err := os.WriteFile(tempPath, data, perm); err != nil {
+		return fmt.Errorf("failed to write temp file: %w", err)
+	}
+	if err := os.Rename(tempPath, filePath); err != nil {
+		if removeErr := os.Remove(tempPath); removeErr != nil && !os.IsNotExist(removeErr) {
+			log.Printf("WARNING: Failed to cleanup temp file %s: %v", tempPath, removeErr)
+		}
+		return fmt.Errorf("failed to rename temp file: %w", err)
+	}
+	return nil
+}
+
 // loggerSetupFunc is a function type that sets up a logger instance after the log file is opened.
 // It receives the opened file, logDir, and fileName, and returns the configured logger.
 type loggerSetupFunc[T closableLogger] func(file *os.File, logDir, fileName string) (T, error)

internal/logger/observed_url_domains_logger.go

@@ -6,9 +6,10 @@ import (
 	"log"
 	"os"
 	"path/filepath"
-	"sort"
 	"sync"
 	"sync/atomic"
+
+	"github.com/github/gh-aw-mcpg/internal/strutil"
 )
 
 const observedURLDomainsFileName = "observed-url-domains.json"
@@ -117,12 +118,7 @@ func (l *ObservedURLDomainsLogger) LogDomains(serverID string, domains []string)
 func (l *ObservedURLDomainsLogger) writeToFile() error {
 	serialized := make(map[string][]string, len(l.data))
 	for serverID, domains := range l.data {
-		items := make([]string, 0, len(domains))
-		for domain := range domains {
-			items = append(items, domain)
-		}
-		sort.Strings(items)
-		serialized[serverID] = items
+		serialized[serverID] = strutil.SortedSetKeys(domains)
 	}
 
 	jsonData, err := json.MarshalIndent(serialized, "", "  ")
@@ -131,17 +127,7 @@ func (l *ObservedURLDomainsLogger) writeToFile() error {
 	}
 
 	filePath := filepath.Join(l.logDir, l.fileName)
-	tempPath := filePath + ".tmp"
-	if err := os.WriteFile(tempPath, jsonData, 0600); err != nil {
-		return fmt.Errorf("failed to write temp file: %w", err)
-	}
-	if err := os.Rename(tempPath, filePath); err != nil {
-		if removeErr := os.Remove(tempPath); removeErr != nil && !os.IsNotExist(removeErr) {
-			log.Printf("WARNING: Failed to cleanup temp observed URL domains file %s: %v", tempPath, removeErr)
-		}
-		return fmt.Errorf("failed to rename temp file: %w", err)
-	}
-	return nil
+	return atomicWriteFile(filePath, jsonData, 0600)
 }
 
 func (l *ObservedURLDomainsLogger) Close() error { return nil }

internal/logger/tools_logger.go

@@ -112,19 +112,7 @@ func (tl *ToolsLogger) writeToFile() error {
 		return fmt.Errorf("failed to marshal tools data: %w", err)
 	}
 
-	// Write to file atomically using a temp file + rename
-	tempPath := filePath + ".tmp"
-	if err := os.WriteFile(tempPath, jsonData, 0644); err != nil {
-		return fmt.Errorf("failed to write temp file: %w", err)
-	}
-
-	if err := os.Rename(tempPath, filePath); err != nil {
-		// Clean up temp file on error
-		os.Remove(tempPath)
-		return fmt.Errorf("failed to rename temp file: %w", err)
-	}
-
-	return nil
+	return atomicWriteFile(filePath, jsonData, 0644)
 }
 
 // Close is a no-op for ToolsLogger (implements closableLogger interface)

internal/strutil/strutil.go

@@ -5,6 +5,17 @@ import (
 	"strings"
 )
 
+// SortedSetKeys returns the keys of a string set (map[string]struct{}) as a sorted slice.
+// Returns an empty (non-nil) slice when the set is empty.
+func SortedSetKeys(set map[string]struct{}) []string {
+	keys := make([]string, 0, len(set))
+	for k := range set {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	return keys
+}
+
 // DeduplicateStrings returns a new slice with whitespace-trimmed, empty, and duplicate
 // entries removed from input. When sorted is true the result is sorted in ascending order.
 // The relative order of first-seen entries is preserved when sorted is false.

internal/strutil/util_test.go

@@ -6,6 +6,32 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func TestSortedSetKeys(t *testing.T) {
+	t.Parallel()
+
+	t.Run("returns sorted keys", func(t *testing.T) {
+		t.Parallel()
+		set := map[string]struct{}{"banana": {}, "apple": {}, "cherry": {}}
+		assert.Equal(t, []string{"apple", "banana", "cherry"}, SortedSetKeys(set))
+	})
+
+	t.Run("returns empty slice for empty set", func(t *testing.T) {
+		t.Parallel()
+		assert.Empty(t, SortedSetKeys(map[string]struct{}{}))
+	})
+
+	t.Run("returns single element slice", func(t *testing.T) {
+		t.Parallel()
+		set := map[string]struct{}{"only": {}}
+		assert.Equal(t, []string{"only"}, SortedSetKeys(set))
+	})
+
+	t.Run("handles nil map", func(t *testing.T) {
+		t.Parallel()
+		assert.Empty(t, SortedSetKeys(nil))
+	})
+}
+
 func TestGetStringFromMap(t *testing.T) {
 	t.Parallel()
 

internal/urlutil/domains.go

@@ -3,10 +3,10 @@ package urlutil
 import (
 	"net/url"
 	"regexp"
-	"sort"
 	"strings"
 
 	"github.com/github/gh-aw-mcpg/internal/logger"
+	"github.com/github/gh-aw-mcpg/internal/strutil"
 )
 
 var logDomains = logger.New("urlutil:domains")
@@ -26,11 +26,7 @@ func ExtractURLDomainsFromValue(value any) []string {
 		return nil
 	}
 
-	domains := make([]string, 0, len(domainSet))
-	for domain := range domainSet {
-		domains = append(domains, domain)
-	}
-	sort.Strings(domains)
+	domains := strutil.SortedSetKeys(domainSet)
 	logDomains.Printf("ExtractURLDomainsFromValue: extracted %d unique domain(s)", len(domains))
 	return domains
 }
@@ -91,11 +87,7 @@ func ExtractURLDomains(text string) []string {
 	if len(domainSet) == 0 {
 		return nil
 	}
-	domains := make([]string, 0, len(domainSet))
-	for domain := range domainSet {
-		domains = append(domains, domain)
-	}
-	sort.Strings(domains)
+	domains := strutil.SortedSetKeys(domainSet)
 	logDomains.Printf("ExtractURLDomains: resolved %d unique domain(s) from %d candidate(s)", len(domains), len(matches))
 	return domains
 }