cmd/go/internal/mvs: Minimal Version Selection

vendor/cmd/go/internal/mvs/mvs.go

diff --git a/vendor/cmd/go/internal/mvs/mvs.go b/vendor/cmd/go/internal/mvs/mvs.go
new file mode 100644
index 0000000..c7ddb6f
--- /dev/null
+++ b/vendor/cmd/go/internal/mvs/mvs.go
@@ -0,0 +1,301 @@
+// Copyright 2018 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 mvs implements Minimal Version Selection.
+// See https://research.swtch.com/vgo3.
+package mvs
+
+import (
+	"fmt"
+	"sort"
+
+	"cmd/go/internal/module"
+)
+
+type Reqs interface {
+	Required(m module.Version) ([]module.Version, error)
+	Max(v1, v2 string) string
+	Latest(path string) (module.Version, error)
+	Previous(m module.Version) (module.Version, error)
+}
+
+type MissingModuleError struct {
+	Module module.Version
+}
+
+func (e *MissingModuleError) Error() string {
+	return fmt.Sprintf("missing module: %v", e.Module)
+}
+
+// BuildList returns the build list for the target module.
+func BuildList(target module.Version, reqs Reqs) ([]module.Version, error) {
+	return buildList(target, reqs, nil, nil)
+}
+
+func buildList(target module.Version, reqs Reqs, uses map[module.Version][]module.Version, vers map[string]string) ([]module.Version, error) {
+	var (
+		min  = map[string]string{target.Path: target.Version}
+		todo = []module.Version{target}
+		seen = map[module.Version]bool{target: true}
+	)
+	for len(todo) > 0 {
+		m := todo[len(todo)-1]
+		todo = todo[:len(todo)-1]
+		required, _ := reqs.Required(m)
+		for _, r := range required {
+			if uses != nil {
+				uses[r] = append(uses[r], m)
+			}
+			if !seen[r] {
+				if v, ok := min[r.Path]; !ok {
+					min[r.Path] = r.Version
+				} else if max := reqs.Max(v, r.Version); max != v {
+					min[r.Path] = max
+				}
+				todo = append(todo, r)
+				seen[r] = true
+			}
+		}
+	}
+
+	if min[target.Path] != target.Version {
+		panic("unbuildable") // TODO
+	}
+
+	if vers == nil {
+		vers = make(map[string]string)
+	}
+	list := []module.Version{target}
+	for i := 0; i < len(list); i++ {
+		m := list[i]
+		required, err := reqs.Required(m)
+		if err != nil {
+			// TODO: Check error is decent.
+			return nil, err
+		}
+		for _, r := range required {
+			v := min[r.Path]
+			if reqs.Max(v, r.Version) != v {
+				panic("mistake") // TODO
+			}
+			if _, ok := vers[r.Path]; !ok {
+				vers[r.Path] = v
+				list = append(list, module.Version{r.Path, v})
+			}
+		}
+	}
+	tail := list[1:]
+	sort.Slice(tail, func(i, j int) bool {
+		return tail[i].Path < tail[j].Path
+	})
+	return list, nil
+}
+
+// Req returns the minimal requirement list for the target module
+// that result in the given build list.
+func Req(target module.Version, list []module.Version, reqs Reqs) ([]module.Version, error) {
+	// Compute postorder, cache requirements.
+	var postorder []module.Version
+	reqCache := map[module.Version][]module.Version{}
+	reqCache[target] = nil
+	var walk func(module.Version) error
+	walk = func(m module.Version) error {
+		_, ok := reqCache[m]
+		if ok {
+			return nil
+		}
+		required, err := reqs.Required(m)
+		if err != nil {
+			return err
+		}
+		reqCache[m] = required
+		for _, m1 := range required {
+			if err := walk(m1); err != nil {
+				return err
+			}
+		}
+		postorder = append(postorder, m)
+		return nil
+	}
+	for _, m := range list {
+		if err := walk(m); err != nil {
+			return nil, err
+		}
+	}
+
+	// Walk modules in reverse post-order, only adding those not implied already.
+	have := map[string]string{}
+	walk = func(m module.Version) error {
+		if v, ok := have[m.Path]; ok && reqs.Max(m.Version, v) == v {
+			return nil
+		}
+		have[m.Path] = m.Version
+		for _, m1 := range reqCache[m] {
+			walk(m1)
+		}
+		return nil
+	}
+	max := map[string]string{}
+	for _, m := range list {
+		if max[m.Path] == "" {
+			max[m.Path] = m.Version
+		} else {
+			max[m.Path] = reqs.Max(m.Version, max[m.Path])
+		}
+	}
+	var min []module.Version
+	for i := len(postorder) - 1; i >= 0; i-- {
+		m := postorder[i]
+		if max[m.Path] != m.Version {
+			// Older version.
+			continue
+		}
+		if have[m.Path] != m.Version {
+			min = append(min, m)
+			walk(m)
+		}
+	}
+	sort.Slice(min, func(i, j int) bool {
+		return min[i].Path < min[j].Path
+	})
+	return min, nil
+}
+
+// UpgradeAll returns a build list for the target module
+// in which every module is upgraded to its latest version.
+func UpgradeAll(target module.Version, reqs Reqs) ([]module.Version, error) {
+	have := map[string]bool{target.Path: true}
+	list := []module.Version{target}
+	for i := 0; i < len(list); i++ {
+		m := list[i]
+		required, err := reqs.Required(m)
+		if err != nil {
+			panic(err) // TODO
+		}
+		for _, r := range required {
+			latest, err := reqs.Latest(r.Path)
+			if err != nil {
+				panic(err) // TODO
+			}
+			if reqs.Max(latest.Version, r.Version) != latest.Version {
+				panic("mistake") // TODO
+			}
+			if !have[r.Path] {
+				have[r.Path] = true
+				list = append(list, module.Version{r.Path, latest.Version})
+			}
+		}
+	}
+	tail := list[1:]
+	sort.Slice(tail, func(i, j int) bool {
+		return tail[i].Path < tail[j].Path
+	})
+	return list, nil
+}
+
+// Upgrade returns a build list for the target module
+// in which the given additional modules are upgraded.
+func Upgrade(target module.Version, reqs Reqs, upgrade ...module.Version) ([]module.Version, error) {
+	list, err := reqs.Required(target)
+	if err != nil {
+		panic(err) // TODO
+	}
+	// TODO: Maybe if an error is given,
+	// rerun with BuildList(upgrade[0], reqs) etc
+	// to find which ones are the buggy ones.
+	list = append([]module.Version(nil), list...)
+	list = append(list, upgrade...)
+	return BuildList(target, &override{target, list, reqs})
+}
+
+// Downgrade returns a build list for the target module
+// in which the given additional modules are downgraded.
+func Downgrade(target module.Version, reqs Reqs, downgrade ...module.Version) ([]module.Version, error) {
+	list, err := reqs.Required(target)
+	if err != nil {
+		panic(err) // TODO
+	}
+	max := make(map[string]string)
+	for _, r := range list {
+		max[r.Path] = r.Version
+	}
+	for _, d := range downgrade {
+		if v, ok := max[d.Path]; !ok || reqs.Max(v, d.Version) != d.Version {
+			max[d.Path] = d.Version
+		}
+	}
+
+	var (
+		added    = make(map[module.Version]bool)
+		rdeps    = make(map[module.Version][]module.Version)
+		excluded = make(map[module.Version]bool)
+	)
+	var exclude func(module.Version)
+	exclude = func(m module.Version) {
+		if excluded[m] {
+			return
+		}
+		excluded[m] = true
+		for _, p := range rdeps[m] {
+			exclude(p)
+		}
+	}
+	var add func(module.Version)
+	add = func(m module.Version) {
+		if added[m] {
+			return
+		}
+		added[m] = true
+		if v, ok := max[m.Path]; ok && reqs.Max(m.Version, v) != v {
+			exclude(m)
+			return
+		}
+		list, err := reqs.Required(m)
+		if err != nil {
+			panic(err) // TODO
+		}
+		for _, r := range list {
+			add(r)
+			if excluded[r] {
+				exclude(m)
+				return
+			}
+			rdeps[r] = append(rdeps[r], m)
+		}
+	}
+
+	var out []module.Version
+	out = append(out, target)
+List:
+	for _, r := range list {
+		add(r)
+		for excluded[r] {
+			p, err := reqs.Previous(r)
+			if err != nil {
+				return nil, err // TODO
+			}
+			if p.Version == "none" {
+				continue List
+			}
+			add(p)
+			r = p
+		}
+		out = append(out, r)
+	}
+
+	return out, nil
+}
+
+type override struct {
+	target module.Version
+	list   []module.Version
+	Reqs
+}
+
+func (r *override) Required(m module.Version) ([]module.Version, error) {
+	if m == r.target {
+		return r.list, nil
+	}
+	return r.Reqs.Required(m)
+}

vendor/cmd/go/internal/mvs/mvs_test.go

diff --git a/vendor/cmd/go/internal/mvs/mvs_test.go b/vendor/cmd/go/internal/mvs/mvs_test.go
new file mode 100644
index 0000000..26b2305
--- /dev/null
+++ b/vendor/cmd/go/internal/mvs/mvs_test.go
@@ -0,0 +1,343 @@
+// Copyright 2018 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 mvs
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+
+	"cmd/go/internal/module"
+)
+
+var tests = `
+# Scenario from blog.
+name: blog
+A: B1 C2
+B1: D3
+C1: D2
+C2: D4
+C3: D5
+C4: G1
+D2: E1
+D3: E2
+D4: E2 F1
+D5: E2
+G1: C4
+A2: B1 C4 D4
+build A: A B1 C2 D4 E2 F1
+upgrade* A: A B1 C4 D5 E2 G1
+upgrade A C4: A B1 C4 D4 E2 F1 G1
+downgrade A2 D2: A2 C4 D2
+
+# Cross-dependency between D and E.
+# No matter how it arises, should get result of merging all build lists via max,
+# which leads to including both D2 and E2.
+
+name: cross1
+A: B C
+B: D1
+C: D2
+D1: E2
+D2: E1
+build A: A B C D2 E2
+
+name: cross1V
+A: B2 C D2 E1
+B1: 
+B2: D1
+C: D2
+D1: E2
+D2: E1
+build A: A B2 C D2 E2
+
+name: cross1U
+A: B1 C
+B1: 
+B2: D1
+C: D2
+D1: E2
+D2: E1
+build A: A B1 C D2 E1
+upgrade A B2: A B2 C D2 E2
+
+name: cross1R
+A: B C 
+B: D2
+C: D1
+D1: E2
+D2: E1
+build A: A B C D2 E2
+
+name: cross1X
+A: B C
+B: D1 E2
+C: D2
+D1: E2
+D2: E1
+build A: A B C D2 E2
+
+name: cross2
+A: B D2
+B: D1
+D1: E2
+D2: E1
+build A: A B D2 E2
+
+name: cross2X
+A: B D2
+B: D1 E2
+C: D2
+D1: E2
+D2: E1
+build A: A B D2 E2
+
+name: cross3
+A: B D2 E1
+B: D1
+D1: E2
+D2: E1
+build A: A B D2 E2
+
+name: cross3X
+A: B D2 E1
+B: D1 E2
+D1: E2
+D2: E1
+build A: A B D2 E2
+
+# Should not get E2 here, because B has been updated
+# not to depend on D1 anymore.
+name: cross4
+A1: B1 D2
+A2: B2 D2
+B1: D1
+B2: D2
+D1: E2
+D2: E1
+build A1: A1 B1 D2 E2
+build A2: A2 B2 D2 E1
+
+# But the upgrade from A1 preserves the E2 dep explicitly.
+upgrade A1 B2: A1 B2 D2 E2
+upgradereq A1 B2: B2 E2
+
+name: cross5
+A: D1
+D1: E2
+D2: E1
+build A: A D1 E2
+upgrade* A: A D2 E2
+upgrade A D2: A D2 E2
+upgradereq A D2: D2 E2
+
+name: cross6
+A: D2
+D1: E2
+D2: E1
+build A: A D2 E1
+upgrade* A: A D2 E2
+upgrade A E2: A D2 E2
+
+name: cross7
+A: B C
+B: D1
+C: E1
+D1: E2
+E1: D2
+build A: A B C D2 E2
+
+name: down1
+A: B2
+B1: C1
+B2: C2
+build A: A B2 C2
+downgrade A C1: A B1
+
+name: down2
+A: B2 E2
+B1:
+B2: C2 F2
+C1:
+D1:
+C2: D2 E2
+D2: B2
+E2: D2
+E1:
+F1:
+downgrade A F1: A B1 E1
+
+name: down3
+A: 
+`
+
+func Test(t *testing.T) {
+	var (
+		name string
+		reqs reqsMap
+		fns  []func(*testing.T)
+	)
+	flush := func() {
+		if name != "" {
+			t.Run(name, func(t *testing.T) {
+				for _, fn := range fns {
+					fn(t)
+				}
+			})
+		}
+	}
+	m := func(s string) module.Version {
+		return module.Version{s[:1], s[1:]}
+	}
+	ms := func(list []string) []module.Version {
+		var mlist []module.Version
+		for _, s := range list {
+			mlist = append(mlist, m(s))
+		}
+		return mlist
+	}
+	checkList := func(t *testing.T, desc string, list []module.Version, err error, val string) {
+		if err != nil {
+			t.Fatalf("%s: %v", desc, err)
+		}
+		vs := ms(strings.Fields(val))
+		if !reflect.DeepEqual(list, vs) {
+			t.Errorf("%s = %v, want %v", desc, list, vs)
+		}
+	}
+
+	for _, line := range strings.Split(tests, "\n") {
+		line = strings.TrimSpace(line)
+		if strings.HasPrefix(line, "#") || line == "" {
+			continue
+		}
+		i := strings.Index(line, ":")
+		if i < 0 {
+			t.Fatalf("missing colon: %q", line)
+		}
+		key := strings.TrimSpace(line[:i])
+		val := strings.TrimSpace(line[i+1:])
+		if key == "" {
+			t.Fatalf("missing key: %q", line)
+		}
+		kf := strings.Fields(key)
+		switch kf[0] {
+		case "name":
+			if len(kf) != 1 {
+				t.Fatalf("name takes no arguments: %q", line)
+			}
+			flush()
+			reqs = make(reqsMap)
+			fns = nil
+			name = val
+			continue
+		case "build":
+			if len(kf) != 2 {
+				t.Fatalf("build takes one argument: %q", line)
+			}
+			fns = append(fns, func(t *testing.T) {
+				list, err := BuildList(m(kf[1]), reqs)
+				checkList(t, key, list, err, val)
+			})
+			continue
+		case "upgrade*":
+			if len(kf) != 2 {
+				t.Fatalf("upgrade* takes one argument: %q", line)
+			}
+			fns = append(fns, func(t *testing.T) {
+				list, err := UpgradeAll(m(kf[1]), reqs)
+				checkList(t, key, list, err, val)
+			})
+			continue
+		case "upgradereq":
+			if len(kf) < 2 {
+				t.Fatalf("upgrade takes at least one arguments: %q", line)
+			}
+			fns = append(fns, func(t *testing.T) {
+				list, err := Upgrade(m(kf[1]), reqs, ms(kf[2:])...)
+				if err == nil {
+					list, err = Req(m(kf[1]), list, reqs)
+				}
+				checkList(t, key, list, err, val)
+			})
+			continue
+		case "upgrade":
+			if len(kf) < 2 {
+				t.Fatalf("upgrade takes at least one arguments: %q", line)
+			}
+			fns = append(fns, func(t *testing.T) {
+				list, err := Upgrade(m(kf[1]), reqs, ms(kf[2:])...)
+				checkList(t, key, list, err, val)
+			})
+			continue
+		case "downgrade":
+			if len(kf) < 2 {
+				t.Fatalf("downgrade takes at least one arguments: %q", line)
+			}
+			fns = append(fns, func(t *testing.T) {
+				list, err := Downgrade(m(kf[1]), reqs, ms(kf[1:])...)
+				checkList(t, key, list, err, val)
+			})
+			continue
+		}
+		if len(kf) == 1 && 'A' <= key[0] && key[0] <= 'Z' {
+			var rs []module.Version
+			for _, f := range strings.Fields(val) {
+				r := m(f)
+				if reqs[r] == nil {
+					reqs[r] = []module.Version{}
+				}
+				rs = append(rs, r)
+			}
+			reqs[m(key)] = rs
+			continue
+		}
+		t.Fatalf("bad line: %q", line)
+	}
+	flush()
+}
+
+type reqsMap map[module.Version][]module.Version
+
+func (r reqsMap) Max(v1, v2 string) string {
+	if v1 < v2 {
+		return v2
+	}
+	return v1
+}
+
+func (r reqsMap) Latest(path string) (module.Version, error) {
+	var m module.Version
+	for k := range r {
+		if k.Path == path && m.Version < k.Version {
+			m = k
+		}
+	}
+	if m.Path == "" {
+		return module.Version{}, &MissingModuleError{module.Version{path, ""}}
+	}
+	return m, nil
+}
+
+func (r reqsMap) Previous(m module.Version) (module.Version, error) {
+	var p module.Version
+	for k := range r {
+		if k.Path == m.Path && p.Version < k.Version && k.Version < m.Version {
+			p = k
+		}
+	}
+	if p.Path == "" {
+		return module.Version{m.Path, "none"}, nil
+	}
+	return p, nil
+}
+
+func (r reqsMap) Required(m module.Version) ([]module.Version, error) {
+	rr, ok := r[m]
+	if !ok {
+		return nil, &MissingModuleError{m}
+	}
+	return rr, nil
+}