podman

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// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package packages
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import (
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	"fmt"
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	"os"
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	"sort"
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)
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// Visit visits all the packages in the import graph whose roots are
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// pkgs, calling the optional pre function the first time each package
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// is encountered (preorder), and the optional post function after a
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// package's dependencies have been visited (postorder).
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// The boolean result of pre(pkg) determines whether
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// the imports of package pkg are visited.
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func Visit(pkgs []*Package, pre func(*Package) bool, post func(*Package)) {
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	seen := make(map[*Package]bool)
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	var visit func(*Package)
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	visit = func(pkg *Package) {
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		if !seen[pkg] {
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			seen[pkg] = true
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			if pre == nil || pre(pkg) {
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				paths := make([]string, 0, len(pkg.Imports))
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				for path := range pkg.Imports {
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					paths = append(paths, path)
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				}
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				sort.Strings(paths) // Imports is a map, this makes visit stable
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				for _, path := range paths {
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					visit(pkg.Imports[path])
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				}
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			}
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			if post != nil {
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				post(pkg)
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			}
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		}
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	}
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	for _, pkg := range pkgs {
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		visit(pkg)
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	}
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}
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// PrintErrors prints to os.Stderr the accumulated errors of all
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// packages in the import graph rooted at pkgs, dependencies first.
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// PrintErrors returns the number of errors printed.
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func PrintErrors(pkgs []*Package) int {
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	var n int
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	Visit(pkgs, nil, func(pkg *Package) {
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		for _, err := range pkg.Errors {
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			fmt.Fprintln(os.Stderr, err)
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			n++
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		}
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	})
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	return n
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}
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