Initialize module and dependencies

vendor/golang.org/x/tools/internal/modindex/modindex.go

@@ -0,0 +1,119 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package modindex contains code for building and searching an
+// [Index] of the Go module cache.
+package modindex
+
+// The directory containing the index, returned by
+// [IndexDir], contains a file index-name-<ver> that contains the name
+// of the current index. We believe writing that short file is atomic.
+// [Read] reads that file to get the file name of the index.
+// WriteIndex writes an index with a unique name and then
+// writes that name into a new version of index-name-<ver>.
+// (<ver> stands for the CurrentVersion of the index format.)
+
+import (
+	"maps"
+	"os"
+	"path/filepath"
+	"slices"
+	"strings"
+	"time"
+
+	"golang.org/x/mod/semver"
+)
+
+// Update updates the index for the specified Go
+// module cache directory, creating it as needed.
+// On success it returns the current index.
+func Update(gomodcache string) (*Index, error) {
+	prev, err := Read(gomodcache)
+	if err != nil {
+		if !os.IsNotExist(err) {
+			return nil, err
+		}
+		prev = nil
+	}
+	return update(gomodcache, prev)
+}
+
+// update builds, writes, and returns the current index.
+//
+// If old is nil, the new index is built from all of GOMODCACHE;
+// otherwise it is built from the old index plus cache updates
+// since the previous index's time.
+func update(gomodcache string, old *Index) (*Index, error) {
+	gomodcache, err := filepath.Abs(gomodcache)
+	if err != nil {
+		return nil, err
+	}
+	new, changed, err := build(gomodcache, old)
+	if err != nil {
+		return nil, err
+	}
+	if old == nil || changed {
+		if err := write(gomodcache, new); err != nil {
+			return nil, err
+		}
+	}
+	return new, nil
+}
+
+// build returns a new index for the specified Go module cache (an
+// absolute path).
+//
+// If an old index is provided, only directories more recent than it
+// that it are scanned; older directories are provided by the old
+// Index.
+//
+// The boolean result indicates whether new entries were found.
+func build(gomodcache string, old *Index) (*Index, bool, error) {
+	// Set the time window.
+	var start time.Time // = dawn of time
+	if old != nil {
+		start = old.ValidAt
+	}
+	now := time.Now()
+	end := now.Add(24 * time.Hour) // safely in the future
+
+	// Enumerate GOMODCACHE package directories.
+	// Choose the best (latest) package for each import path.
+	pkgDirs := findDirs(gomodcache, start, end)
+	dirByPath, err := bestDirByImportPath(pkgDirs)
+	if err != nil {
+		return nil, false, err
+	}
+
+	// For each import path it might occur only in
+	// dirByPath, only in old, or in both.
+	// If both, use the semantically later one.
+	var entries []Entry
+	if old != nil {
+		for _, entry := range old.Entries {
+			dir, ok := dirByPath[entry.ImportPath]
+			if !ok || semver.Compare(dir.version, entry.Version) <= 0 {
+				// New dir is missing or not more recent; use old entry.
+				entries = append(entries, entry)
+				delete(dirByPath, entry.ImportPath)
+			}
+		}
+	}
+
+	// Extract symbol information for all the new directories.
+	newEntries := extractSymbols(gomodcache, maps.Values(dirByPath))
+	entries = append(entries, newEntries...)
+	slices.SortFunc(entries, func(x, y Entry) int {
+		if n := strings.Compare(x.PkgName, y.PkgName); n != 0 {
+			return n
+		}
+		return strings.Compare(x.ImportPath, y.ImportPath)
+	})
+
+	return &Index{
+		GOMODCACHE: gomodcache,
+		ValidAt:    now, // time before the directories were scanned
+		Entries:    entries,
+	}, len(newEntries) > 0, nil
+}