several: use stdlib functions

Replace some functions with simpler code that uses
recent functions added to the standard library.

Change-Id: Ifcd570679a897fb165a4307c7ce9f0f53fccea05
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/609116
kokoro-CI: kokoro <noreply+kokoro@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>

internal/licenses/licenses.go

@@ -26,8 +26,10 @@ import (
 	"fmt"
 	"io"
 	"io/fs"
+	"maps"
 	"path"
 	"path/filepath"
+	"slices"
 	"sort"
 	"strings"
 	"sync"
@@ -575,7 +577,7 @@ func DetectFile(contents []byte, filename string, logf func(string, ...any)) ([]
 		logf("%s failed to classify license (%+v), skipping", filename, cov)
 		return []string{unknownLicenseType}, cov
 	}
-	return setToSortedSlice(types), cov
+	return slices.Sorted(maps.Keys(types)), cov
 }
 
 // Redistributable reports whether the set of license types establishes that a
@@ -603,12 +605,3 @@ func types(lics []*License) []string {
 	}
 	return types
 }
-
-func setToSortedSlice(m map[string]bool) []string {
-	var s []string
-	for e := range m {
-		s = append(s, e)
-	}
-	sort.Strings(s)
-	return s
-}

internal/postgres/insert_module.go

@@ -12,6 +12,8 @@ import (
 	"fmt"
 	"hash/fnv"
 	"io"
+	"maps"
+	"slices"
 	"sort"
 	"strings"
 	"unicode/utf8"
@@ -442,15 +444,7 @@ func insertPaths(ctx context.Context, tx *database.DB, m *internal.Module) (path
 		curPathsSet[internal.V1Path(u.Path, m.ModulePath)] = true
 		curPathsSet[internal.SeriesPathForModule(m.ModulePath)] = true
 	}
-	return upsertPaths(ctx, tx, stringSetToSlice(curPathsSet))
-}
-
-func stringSetToSlice(m map[string]bool) []string {
-	var s []string
-	for e := range m {
-		s = append(s, e)
-	}
-	return s
+	return upsertPaths(ctx, tx, slices.Collect(maps.Keys(curPathsSet)))
 }
 
 func insertUnits(ctx context.Context, db *database.DB, unitValues []any) (pathIDToUnitID map[int]int, err error) {
@@ -581,7 +575,7 @@ func insertImports(ctx context.Context, tx *database.DB,
 			importPathSet[imp] = true
 		}
 	}
-	pathToID, err := upsertPaths(ctx, tx, stringSetToSlice(importPathSet))
+	pathToID, err := upsertPaths(ctx, tx, slices.Collect(maps.Keys(importPathSet)))
 	if err != nil {
 		return err
 	}