Current File : //usr/local/go/src/cmd/go/internal/modload/buildlist.go
// 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 modload
import (
"cmd/go/internal/base"
"cmd/go/internal/cfg"
"cmd/go/internal/mvs"
"cmd/go/internal/par"
"context"
"fmt"
"os"
"reflect"
"runtime"
"runtime/debug"
"strings"
"sync"
"sync/atomic"
"golang.org/x/mod/module"
"golang.org/x/mod/semver"
)
// capVersionSlice returns s with its cap reduced to its length.
func capVersionSlice(s []module.Version) []module.Version {
return s[:len(s):len(s)]
}
// A Requirements represents a logically-immutable set of root module requirements.
type Requirements struct {
// depth is the depth at which the requirement graph is computed.
//
// If eager, the graph includes all transitive requirements regardless of depth.
//
// If lazy, the graph includes only the root modules, the explicit
// requirements of those root modules, and the transitive requirements of only
// the *non-lazy* root modules.
depth modDepth
// rootModules is the set of module versions explicitly required by the main
// module, sorted and capped to length. It may contain duplicates, and may
// contain multiple versions for a given module path.
rootModules []module.Version
maxRootVersion map[string]string
// direct is the set of module paths for which we believe the module provides
// a package directly imported by a package or test in the main module.
//
// The "direct" map controls which modules are annotated with "// indirect"
// comments in the go.mod file, and may impact which modules are listed as
// explicit roots (vs. indirect-only dependencies). However, it should not
// have a semantic effect on the build list overall.
//
// The initial direct map is populated from the existing "// indirect"
// comments (or lack thereof) in the go.mod file. It is updated by the
// package loader: dependencies may be promoted to direct if new
// direct imports are observed, and may be demoted to indirect during
// 'go mod tidy' or 'go mod vendor'.
//
// The direct map is keyed by module paths, not module versions. When a
// module's selected version changes, we assume that it remains direct if the
// previous version was a direct dependency. That assumption might not hold in
// rare cases (such as if a dependency splits out a nested module, or merges a
// nested module back into a parent module).
direct map[string]bool
graphOnce sync.Once // guards writes to (but not reads from) graph
graph atomic.Value // cachedGraph
}
// A cachedGraph is a non-nil *ModuleGraph, together with any error discovered
// while loading that graph.
type cachedGraph struct {
mg *ModuleGraph
err error // If err is non-nil, mg may be incomplete (but must still be non-nil).
}
// requirements is the requirement graph for the main module.
//
// It is always non-nil if the main module's go.mod file has been loaded.
//
// This variable should only be read from the loadModFile function, and should
// only be written in the loadModFile and commitRequirements functions.
// All other functions that need or produce a *Requirements should
// accept and/or return an explicit parameter.
var requirements *Requirements
// newRequirements returns a new requirement set with the given root modules.
// The dependencies of the roots will be loaded lazily at the first call to the
// Graph method.
//
// The rootModules slice must be sorted according to module.Sort.
// The caller must not modify the rootModules slice or direct map after passing
// them to newRequirements.
//
// If vendoring is in effect, the caller must invoke initVendor on the returned
// *Requirements before any other method.
func newRequirements(depth modDepth, rootModules []module.Version, direct map[string]bool) *Requirements {
for i, m := range rootModules {
if m == Target {
panic(fmt.Sprintf("newRequirements called with untrimmed build list: rootModules[%v] is Target", i))
}
if m.Path == "" || m.Version == "" {
panic(fmt.Sprintf("bad requirement: rootModules[%v] = %v", i, m))
}
if i > 0 {
prev := rootModules[i-1]
if prev.Path > m.Path || (prev.Path == m.Path && semver.Compare(prev.Version, m.Version) > 0) {
panic(fmt.Sprintf("newRequirements called with unsorted roots: %v", rootModules))
}
}
}
rs := &Requirements{
depth: depth,
rootModules: capVersionSlice(rootModules),
maxRootVersion: make(map[string]string, len(rootModules)),
direct: direct,
}
for _, m := range rootModules {
if v, ok := rs.maxRootVersion[m.Path]; ok && cmpVersion(v, m.Version) >= 0 {
continue
}
rs.maxRootVersion[m.Path] = m.Version
}
return rs
}
// initVendor initializes rs.graph from the given list of vendored module
// dependencies, overriding the graph that would normally be loaded from module
// requirements.
func (rs *Requirements) initVendor(vendorList []module.Version) {
rs.graphOnce.Do(func() {
mg := &ModuleGraph{
g: mvs.NewGraph(cmpVersion, []module.Version{Target}),
}
if rs.depth == lazy {
// The roots of a lazy module should already include every module in the
// vendor list, because the vendored modules are the same as those
// maintained as roots by the lazy loading “import invariant”.
//
// Just to be sure, we'll double-check that here.
inconsistent := false
for _, m := range vendorList {
if v, ok := rs.rootSelected(m.Path); !ok || v != m.Version {
base.Errorf("go: vendored module %v should be required explicitly in go.mod", m)
inconsistent = true
}
}
if inconsistent {
base.Fatalf("go: %v", errGoModDirty)
}
// Now we can treat the rest of the module graph as effectively “pruned
// out”, like a more aggressive version of lazy loading: in vendor mode,
// the root requirements *are* the complete module graph.
mg.g.Require(Target, rs.rootModules)
} else {
// The transitive requirements of the main module are not in general available
// from the vendor directory, and we don't actually know how we got from
// the roots to the final build list.
//
// Instead, we'll inject a fake "vendor/modules.txt" module that provides
// those transitive dependencies, and mark it as a dependency of the main
// module. That allows us to elide the actual structure of the module
// graph, but still distinguishes between direct and indirect
// dependencies.
vendorMod := module.Version{Path: "vendor/modules.txt", Version: ""}
mg.g.Require(Target, append(rs.rootModules, vendorMod))
mg.g.Require(vendorMod, vendorList)
}
rs.graph.Store(cachedGraph{mg, nil})
})
}
// rootSelected returns the version of the root dependency with the given module
// path, or the zero module.Version and ok=false if the module is not a root
// dependency.
func (rs *Requirements) rootSelected(path string) (version string, ok bool) {
if path == Target.Path {
return Target.Version, true
}
if v, ok := rs.maxRootVersion[path]; ok {
return v, true
}
return "", false
}
// hasRedundantRoot returns true if the root list contains multiple requirements
// of the same module or a requirement on any version of the main module.
// Redundant requirements should be pruned, but they may influence version
// selection.
func (rs *Requirements) hasRedundantRoot() bool {
for i, m := range rs.rootModules {
if m.Path == Target.Path || (i > 0 && m.Path == rs.rootModules[i-1].Path) {
return true
}
}
return false
}
// Graph returns the graph of module requirements loaded from the current
// root modules (as reported by RootModules).
//
// Graph always makes a best effort to load the requirement graph despite any
// errors, and always returns a non-nil *ModuleGraph.
//
// If the requirements of any relevant module fail to load, Graph also
// returns a non-nil error of type *mvs.BuildListError.
func (rs *Requirements) Graph(ctx context.Context) (*ModuleGraph, error) {
rs.graphOnce.Do(func() {
mg, mgErr := readModGraph(ctx, rs.depth, rs.rootModules)
rs.graph.Store(cachedGraph{mg, mgErr})
})
cached := rs.graph.Load().(cachedGraph)
return cached.mg, cached.err
}
// IsDirect returns whether the given module provides a package directly
// imported by a package or test in the main module.
func (rs *Requirements) IsDirect(path string) bool {
return rs.direct[path]
}
// A ModuleGraph represents the complete graph of module dependencies
// of a main module.
//
// If the main module is lazily loaded, the graph does not include
// transitive dependencies of non-root (implicit) dependencies.
type ModuleGraph struct {
g *mvs.Graph
loadCache par.Cache // module.Version → summaryError
buildListOnce sync.Once
buildList []module.Version
}
// A summaryError is either a non-nil modFileSummary or a non-nil error
// encountered while reading or parsing that summary.
type summaryError struct {
summary *modFileSummary
err error
}
var readModGraphDebugOnce sync.Once
// readModGraph reads and returns the module dependency graph starting at the
// given roots.
//
// Unlike LoadModGraph, readModGraph does not attempt to diagnose or update
// inconsistent roots.
func readModGraph(ctx context.Context, depth modDepth, roots []module.Version) (*ModuleGraph, error) {
if depth == lazy {
readModGraphDebugOnce.Do(func() {
for _, f := range strings.Split(os.Getenv("GODEBUG"), ",") {
switch f {
case "lazymod=log":
debug.PrintStack()
fmt.Fprintf(os.Stderr, "go: read full module graph.\n")
case "lazymod=strict":
debug.PrintStack()
base.Fatalf("go: read full module graph (forbidden by GODEBUG=lazymod=strict).")
}
}
})
}
var (
mu sync.Mutex // guards mg.g and hasError during loading
hasError bool
mg = &ModuleGraph{
g: mvs.NewGraph(cmpVersion, []module.Version{Target}),
}
)
mg.g.Require(Target, roots)
var (
loadQueue = par.NewQueue(runtime.GOMAXPROCS(0))
loadingEager sync.Map // module.Version → nil; the set of modules that have been or are being loaded via eager roots
)
// loadOne synchronously loads the explicit requirements for module m.
// It does not load the transitive requirements of m even if the go version in
// m's go.mod file indicates eager loading.
loadOne := func(m module.Version) (*modFileSummary, error) {
cached := mg.loadCache.Do(m, func() interface{} {
summary, err := goModSummary(m)
mu.Lock()
if err == nil {
mg.g.Require(m, summary.require)
} else {
hasError = true
}
mu.Unlock()
return summaryError{summary, err}
}).(summaryError)
return cached.summary, cached.err
}
var enqueue func(m module.Version, depth modDepth)
enqueue = func(m module.Version, depth modDepth) {
if m.Version == "none" {
return
}
if depth == eager {
if _, dup := loadingEager.LoadOrStore(m, nil); dup {
// m has already been enqueued for loading. Since eager loading may
// follow cycles in the the requirement graph, we need to return early
// to avoid making the load queue infinitely long.
return
}
}
loadQueue.Add(func() {
summary, err := loadOne(m)
if err != nil {
return // findError will report the error later.
}
// If the version in m's go.mod file implies eager loading, then we cannot
// assume that the explicit requirements of m (added by loadOne) are
// sufficient to build the packages it contains. We must load its full
// transitive dependency graph to be sure that we see all relevant
// dependencies.
if depth == eager || summary.depth == eager {
for _, r := range summary.require {
enqueue(r, eager)
}
}
})
}
for _, m := range roots {
enqueue(m, depth)
}
<-loadQueue.Idle()
if hasError {
return mg, mg.findError()
}
return mg, nil
}
// RequiredBy returns the dependencies required by module m in the graph,
// or ok=false if module m's dependencies are not relevant (such as if they
// are pruned out by lazy loading).
//
// The caller must not modify the returned slice, but may safely append to it
// and may rely on it not to be modified.
func (mg *ModuleGraph) RequiredBy(m module.Version) (reqs []module.Version, ok bool) {
return mg.g.RequiredBy(m)
}
// Selected returns the selected version of the module with the given path.
//
// If no version is selected, Selected returns version "none".
func (mg *ModuleGraph) Selected(path string) (version string) {
return mg.g.Selected(path)
}
// WalkBreadthFirst invokes f once, in breadth-first order, for each module
// version other than "none" that appears in the graph, regardless of whether
// that version is selected.
func (mg *ModuleGraph) WalkBreadthFirst(f func(m module.Version)) {
mg.g.WalkBreadthFirst(f)
}
// BuildList returns the selected versions of all modules present in the graph,
// beginning with Target.
//
// The order of the remaining elements in the list is deterministic
// but arbitrary.
//
// The caller must not modify the returned list, but may safely append to it
// and may rely on it not to be modified.
func (mg *ModuleGraph) BuildList() []module.Version {
mg.buildListOnce.Do(func() {
mg.buildList = capVersionSlice(mg.g.BuildList())
})
return mg.buildList
}
func (mg *ModuleGraph) findError() error {
errStack := mg.g.FindPath(func(m module.Version) bool {
cached := mg.loadCache.Get(m)
return cached != nil && cached.(summaryError).err != nil
})
if len(errStack) > 0 {
err := mg.loadCache.Get(errStack[len(errStack)-1]).(summaryError).err
var noUpgrade func(from, to module.Version) bool
return mvs.NewBuildListError(err, errStack, noUpgrade)
}
return nil
}
func (mg *ModuleGraph) allRootsSelected() bool {
roots, _ := mg.g.RequiredBy(Target)
for _, m := range roots {
if mg.Selected(m.Path) != m.Version {
return false
}
}
return true
}
// LoadModGraph loads and returns the graph of module dependencies of the main module,
// without loading any packages.
//
// If the goVersion string is non-empty, the returned graph is the graph
// as interpreted by the given Go version (instead of the version indicated
// in the go.mod file).
//
// Modules are loaded automatically (and lazily) in LoadPackages:
// LoadModGraph need only be called if LoadPackages is not,
// typically in commands that care about modules but no particular package.
func LoadModGraph(ctx context.Context, goVersion string) *ModuleGraph {
rs := LoadModFile(ctx)
if goVersion != "" {
depth := modDepthFromGoVersion(goVersion)
if depth == eager && rs.depth != eager {
// Use newRequirements instead of convertDepth because convertDepth
// also updates roots; here, we want to report the unmodified roots
// even though they may seem inconsistent.
rs = newRequirements(eager, rs.rootModules, rs.direct)
}
mg, err := rs.Graph(ctx)
if err != nil {
base.Fatalf("go: %v", err)
}
return mg
}
rs, mg, err := expandGraph(ctx, rs)
if err != nil {
base.Fatalf("go: %v", err)
}
commitRequirements(ctx, modFileGoVersion(), rs)
return mg
}
// expandGraph loads the complete module graph from rs.
//
// If the complete graph reveals that some root of rs is not actually the
// selected version of its path, expandGraph computes a new set of roots that
// are consistent. (When lazy loading is implemented, this may result in
// upgrades to other modules due to requirements that were previously pruned
// out.)
//
// expandGraph returns the updated roots, along with the module graph loaded
// from those roots and any error encountered while loading that graph.
// expandGraph returns non-nil requirements and a non-nil graph regardless of
// errors. On error, the roots might not be updated to be consistent.
func expandGraph(ctx context.Context, rs *Requirements) (*Requirements, *ModuleGraph, error) {
mg, mgErr := rs.Graph(ctx)
if mgErr != nil {
// Without the graph, we can't update the roots: we don't know which
// versions of transitive dependencies would be selected.
return rs, mg, mgErr
}
if !mg.allRootsSelected() {
// The roots of rs are not consistent with the rest of the graph. Update
// them. In an eager module this is a no-op for the build list as a whole —
// it just promotes what were previously transitive requirements to be
// roots — but in a lazy module it may pull in previously-irrelevant
// transitive dependencies.
newRS, rsErr := updateRoots(ctx, rs.direct, rs, nil, nil, false)
if rsErr != nil {
// Failed to update roots, perhaps because of an error in a transitive
// dependency needed for the update. Return the original Requirements
// instead.
return rs, mg, rsErr
}
rs = newRS
mg, mgErr = rs.Graph(ctx)
}
return rs, mg, mgErr
}
// EditBuildList edits the global build list by first adding every module in add
// to the existing build list, then adjusting versions (and adding or removing
// requirements as needed) until every module in mustSelect is selected at the
// given version.
//
// (Note that the newly-added modules might not be selected in the resulting
// build list: they could be lower than existing requirements or conflict with
// versions in mustSelect.)
//
// If the versions listed in mustSelect are mutually incompatible (due to one of
// the listed modules requiring a higher version of another), EditBuildList
// returns a *ConstraintError and leaves the build list in its previous state.
//
// On success, EditBuildList reports whether the selected version of any module
// in the build list may have been changed (possibly to or from "none") as a
// result.
func EditBuildList(ctx context.Context, add, mustSelect []module.Version) (changed bool, err error) {
rs, changed, err := editRequirements(ctx, LoadModFile(ctx), add, mustSelect)
if err != nil {
return false, err
}
commitRequirements(ctx, modFileGoVersion(), rs)
return changed, err
}
// A ConstraintError describes inconsistent constraints in EditBuildList
type ConstraintError struct {
// Conflict lists the source of the conflict for each version in mustSelect
// that could not be selected due to the requirements of some other version in
// mustSelect.
Conflicts []Conflict
}
func (e *ConstraintError) Error() string {
b := new(strings.Builder)
b.WriteString("version constraints conflict:")
for _, c := range e.Conflicts {
fmt.Fprintf(b, "\n\t%v requires %v, but %v is requested", c.Source, c.Dep, c.Constraint)
}
return b.String()
}
// A Conflict documents that Source requires Dep, which conflicts with Constraint.
// (That is, Dep has the same module path as Constraint but a higher version.)
type Conflict struct {
Source module.Version
Dep module.Version
Constraint module.Version
}
// tidyRoots trims the root dependencies to the minimal requirements needed to
// both retain the same versions of all packages in pkgs and satisfy the
// lazy loading invariants (if applicable).
func tidyRoots(ctx context.Context, rs *Requirements, pkgs []*loadPkg) (*Requirements, error) {
if rs.depth == eager {
return tidyEagerRoots(ctx, rs.direct, pkgs)
}
return tidyLazyRoots(ctx, rs.direct, pkgs)
}
func updateRoots(ctx context.Context, direct map[string]bool, rs *Requirements, pkgs []*loadPkg, add []module.Version, rootsImported bool) (*Requirements, error) {
if rs.depth == eager {
return updateEagerRoots(ctx, direct, rs, add)
}
return updateLazyRoots(ctx, direct, rs, pkgs, add, rootsImported)
}
// tidyLazyRoots returns a minimal set of root requirements that maintains the
// "lazy loading" invariants of the go.mod file for the given packages:
//
// 1. For each package marked with pkgInAll, the module path that provided that
// package is included as a root.
// 2. For all packages, the module that provided that package either remains
// selected at the same version or is upgraded by the dependencies of a
// root.
//
// If any module that provided a package has been upgraded above its previous,
// version, the caller may need to reload and recompute the package graph.
//
// To ensure that the loading process eventually converges, the caller should
// add any needed roots from the tidy root set (without removing existing untidy
// roots) until the set of roots has converged.
func tidyLazyRoots(ctx context.Context, direct map[string]bool, pkgs []*loadPkg) (*Requirements, error) {
var (
roots []module.Version
pathIncluded = map[string]bool{Target.Path: true}
)
// We start by adding roots for every package in "all".
//
// Once that is done, we may still need to add more roots to cover upgraded or
// otherwise-missing test dependencies for packages in "all". For those test
// dependencies, we prefer to add roots for packages with shorter import
// stacks first, on the theory that the module requirements for those will
// tend to fill in the requirements for their transitive imports (which have
// deeper import stacks). So we add the missing dependencies for one depth at
// a time, starting with the packages actually in "all" and expanding outwards
// until we have scanned every package that was loaded.
var (
queue []*loadPkg
queued = map[*loadPkg]bool{}
)
for _, pkg := range pkgs {
if !pkg.flags.has(pkgInAll) {
continue
}
if pkg.fromExternalModule() && !pathIncluded[pkg.mod.Path] {
roots = append(roots, pkg.mod)
pathIncluded[pkg.mod.Path] = true
}
queue = append(queue, pkg)
queued[pkg] = true
}
module.Sort(roots)
tidy := newRequirements(lazy, roots, direct)
for len(queue) > 0 {
roots = tidy.rootModules
mg, err := tidy.Graph(ctx)
if err != nil {
return nil, err
}
prevQueue := queue
queue = nil
for _, pkg := range prevQueue {
m := pkg.mod
if m.Path == "" {
continue
}
for _, dep := range pkg.imports {
if !queued[dep] {
queue = append(queue, dep)
queued[dep] = true
}
}
if pkg.test != nil && !queued[pkg.test] {
queue = append(queue, pkg.test)
queued[pkg.test] = true
}
if !pathIncluded[m.Path] {
if s := mg.Selected(m.Path); cmpVersion(s, m.Version) < 0 {
roots = append(roots, m)
}
pathIncluded[m.Path] = true
}
}
if len(roots) > len(tidy.rootModules) {
module.Sort(roots)
tidy = newRequirements(lazy, roots, tidy.direct)
}
}
_, err := tidy.Graph(ctx)
if err != nil {
return nil, err
}
return tidy, nil
}
// updateLazyRoots returns a set of root requirements that maintains the “lazy
// loading” invariants of the go.mod file:
//
// 1. The selected version of the module providing each package marked with
// either pkgInAll or pkgIsRoot is included as a root.
// Note that certain root patterns (such as '...') may explode the root set
// to contain every module that provides any package imported (or merely
// required) by any other module.
// 2. Each root appears only once, at the selected version of its path
// (if rs.graph is non-nil) or at the highest version otherwise present as a
// root (otherwise).
// 3. Every module path that appears as a root in rs remains a root.
// 4. Every version in add is selected at its given version unless upgraded by
// (the dependencies of) an existing root or another module in add.
//
// The packages in pkgs are assumed to have been loaded from either the roots of
// rs or the modules selected in the graph of rs.
//
// The above invariants together imply the “lazy loading” invariants for the
// go.mod file:
//
// 1. (The import invariant.) Every module that provides a package transitively
// imported by any package or test in the main module is included as a root.
// This follows by induction from (1) and (3) above. Transitively-imported
// packages loaded during this invocation are marked with pkgInAll (1),
// and by hypothesis any transitively-imported packages loaded in previous
// invocations were already roots in rs (3).
//
// 2. (The argument invariant.) Every module that provides a package matching
// an explicit package pattern is included as a root. This follows directly
// from (1): packages matching explicit package patterns are marked with
// pkgIsRoot.
//
// 3. (The completeness invariant.) Every module that contributed any package
// to the build is required by either the main module or one of the modules
// it requires explicitly. This invariant is left up to the caller, who must
// not load packages from outside the module graph but may add roots to the
// graph, but is facilited by (3). If the caller adds roots to the graph in
// order to resolve missing packages, then updateLazyRoots will retain them,
// the selected versions of those roots cannot regress, and they will
// eventually be written back to the main module's go.mod file.
//
// (See https://golang.org/design/36460-lazy-module-loading#invariants for more
// detail.)
func updateLazyRoots(ctx context.Context, direct map[string]bool, rs *Requirements, pkgs []*loadPkg, add []module.Version, rootsImported bool) (*Requirements, error) {
roots := rs.rootModules
rootsUpgraded := false
spotCheckRoot := map[module.Version]bool{}
// “The selected version of the module providing each package marked with
// either pkgInAll or pkgIsRoot is included as a root.”
needSort := false
for _, pkg := range pkgs {
if !pkg.fromExternalModule() {
// pkg was not loaded from a module dependency, so we don't need
// to do anything special to maintain that dependency.
continue
}
switch {
case pkg.flags.has(pkgInAll):
// pkg is transitively imported by a package or test in the main module.
// We need to promote the module that maintains it to a root: if some
// other module depends on the main module, and that other module also
// uses lazy loading, it will expect to find all of our transitive
// dependencies by reading just our go.mod file, not the go.mod files of
// everything we depend on.
//
// (This is the “import invariant” that makes lazy loading possible.)
case rootsImported && pkg.flags.has(pkgFromRoot):
// pkg is a transitive dependency of some root, and we are treating the
// roots as if they are imported by the main module (as in 'go get').
case pkg.flags.has(pkgIsRoot):
// pkg is a root of the package-import graph. (Generally this means that
// it matches a command-line argument.) We want future invocations of the
// 'go' command — such as 'go test' on the same package — to continue to
// use the same versions of its dependencies that we are using right now.
// So we need to bring this package's dependencies inside the lazy-loading
// horizon.
//
// Making the module containing this package a root of the module graph
// does exactly that: if the module containing the package is lazy it
// should satisfy the import invariant itself, so all of its dependencies
// should be in its go.mod file, and if the module containing the package
// is eager then if we make it a root we will load all of its transitive
// dependencies into the module graph.
//
// (This is the “argument invariant” of lazy loading, and is important for
// reproducibility.)
default:
// pkg is a dependency of some other package outside of the main module.
// As far as we know it's not relevant to the main module (and thus not
// relevant to consumers of the main module either), and its dependencies
// should already be in the module graph — included in the dependencies of
// the package that imported it.
continue
}
if _, ok := rs.rootSelected(pkg.mod.Path); ok {
// It is possible that the main module's go.mod file is incomplete or
// otherwise erroneous — for example, perhaps the author forgot to 'git
// add' their updated go.mod file after adding a new package import, or
// perhaps they made an edit to the go.mod file using a third-party tool
// ('git merge'?) that doesn't maintain consistency for module
// dependencies. If that happens, ideally we want to detect the missing
// requirements and fix them up here.
//
// However, we also need to be careful not to be too aggressive. For
// transitive dependencies of external tests, the go.mod file for the
// module containing the test itself is expected to provide all of the
// relevant dependencies, and we explicitly don't want to pull in
// requirements on *irrelevant* requirements that happen to occur in the
// go.mod files for these transitive-test-only dependencies. (See the test
// in mod_lazy_test_horizon.txt for a concrete example.
//
// The “goldilocks zone” seems to be to spot-check exactly the same
// modules that we promote to explicit roots: namely, those that provide
// packages transitively imported by the main module, and those that
// provide roots of the package-import graph. That will catch erroneous
// edits to the main module's go.mod file and inconsistent requirements in
// dependencies that provide imported packages, but will ignore erroneous
// or misleading requirements in dependencies that aren't obviously
// relevant to the packages in the main module.
spotCheckRoot[pkg.mod] = true
} else {
roots = append(roots, pkg.mod)
rootsUpgraded = true
// The roots slice was initially sorted because rs.rootModules was sorted,
// but the root we just added could be out of order.
needSort = true
}
}
for _, m := range add {
if v, ok := rs.rootSelected(m.Path); !ok || cmpVersion(v, m.Version) < 0 {
roots = append(roots, m)
rootsUpgraded = true
needSort = true
}
}
if needSort {
module.Sort(roots)
}
// "Each root appears only once, at the selected version of its path ….”
for {
var mg *ModuleGraph
if rootsUpgraded {
// We've added or upgraded one or more roots, so load the full module
// graph so that we can update those roots to be consistent with other
// requirements.
if cfg.BuildMod != "mod" {
// Our changes to the roots may have moved dependencies into or out of
// the lazy-loading horizon, which could in turn change the selected
// versions of other modules. (Unlike for eager modules, for lazy
// modules adding or removing an explicit root is a semantic change, not
// just a cosmetic one.)
return rs, errGoModDirty
}
rs = newRequirements(lazy, roots, direct)
var err error
mg, err = rs.Graph(ctx)
if err != nil {
return rs, err
}
} else {
// Since none of the roots have been upgraded, we have no reason to
// suspect that they are inconsistent with the requirements of any other
// roots. Only look at the full module graph if we've already loaded it;
// otherwise, just spot-check the explicit requirements of the roots from
// which we loaded packages.
if rs.graph.Load() != nil {
// We've already loaded the full module graph, which includes the
// requirements of all of the root modules — even the transitive
// requirements, if they are eager!
mg, _ = rs.Graph(ctx)
} else if cfg.BuildMod == "vendor" {
// We can't spot-check the requirements of other modules because we
// don't in general have their go.mod files available in the vendor
// directory. (Fortunately this case is impossible, because mg.graph is
// always non-nil in vendor mode!)
panic("internal error: rs.graph is unexpectedly nil with -mod=vendor")
} else if !spotCheckRoots(ctx, rs, spotCheckRoot) {
// We spot-checked the explicit requirements of the roots that are
// relevant to the packages we've loaded. Unfortunately, they're
// inconsistent in some way; we need to load the full module graph
// so that we can fix the roots properly.
var err error
mg, err = rs.Graph(ctx)
if err != nil {
return rs, err
}
}
}
roots = make([]module.Version, 0, len(rs.rootModules))
rootsUpgraded = false
inRootPaths := make(map[string]bool, len(rs.rootModules)+1)
inRootPaths[Target.Path] = true
for _, m := range rs.rootModules {
if inRootPaths[m.Path] {
// This root specifies a redundant path. We already retained the
// selected version of this path when we saw it before, so omit the
// redundant copy regardless of its version.
//
// When we read the full module graph, we include the dependencies of
// every root even if that root is redundant. That better preserves
// reproducibility if, say, some automated tool adds a redundant
// 'require' line and then runs 'go mod tidy' to try to make everything
// consistent, since the requirements of the older version are carried
// over.
//
// So omitting a root that was previously present may *reduce* the
// selected versions of non-roots, but merely removing a requirement
// cannot *increase* the selected versions of other roots as a result —
// we don't need to mark this change as an upgrade. (This particular
// change cannot invalidate any other roots.)
continue
}
var v string
if mg == nil {
v, _ = rs.rootSelected(m.Path)
} else {
v = mg.Selected(m.Path)
}
roots = append(roots, module.Version{Path: m.Path, Version: v})
inRootPaths[m.Path] = true
if v != m.Version {
rootsUpgraded = true
}
}
// Note that rs.rootModules was already sorted by module path and version,
// and we appended to the roots slice in the same order and guaranteed that
// each path has only one version, so roots is also sorted by module path
// and (trivially) version.
if !rootsUpgraded {
if cfg.BuildMod != "mod" {
// The only changes to the root set (if any) were to remove duplicates.
// The requirements are consistent (if perhaps redundant), so keep the
// original rs to preserve its ModuleGraph.
return rs, nil
}
// The root set has converged: every root going into this iteration was
// already at its selected version, although we have have removed other
// (redundant) roots for the same path.
break
}
}
if rs.depth == lazy && reflect.DeepEqual(roots, rs.rootModules) && reflect.DeepEqual(direct, rs.direct) {
// The root set is unchanged and rs was already lazy, so keep rs to
// preserve its cached ModuleGraph (if any).
return rs, nil
}
return newRequirements(lazy, roots, direct), nil
}
// spotCheckRoots reports whether the versions of the roots in rs satisfy the
// explicit requirements of the modules in mods.
func spotCheckRoots(ctx context.Context, rs *Requirements, mods map[module.Version]bool) bool {
ctx, cancel := context.WithCancel(ctx)
defer cancel()
work := par.NewQueue(runtime.GOMAXPROCS(0))
for m := range mods {
m := m
work.Add(func() {
if ctx.Err() != nil {
return
}
summary, err := goModSummary(m)
if err != nil {
cancel()
return
}
for _, r := range summary.require {
if v, ok := rs.rootSelected(r.Path); ok && cmpVersion(v, r.Version) < 0 {
cancel()
return
}
}
})
}
<-work.Idle()
if ctx.Err() != nil {
// Either we failed a spot-check, or the caller no longer cares about our
// answer anyway.
return false
}
return true
}
// tidyEagerRoots returns a minimal set of root requirements that maintains the
// selected version of every module that provided a package in pkgs, and
// includes the selected version of every such module in direct as a root.
func tidyEagerRoots(ctx context.Context, direct map[string]bool, pkgs []*loadPkg) (*Requirements, error) {
var (
keep []module.Version
keptPath = map[string]bool{}
)
var (
rootPaths []string // module paths that should be included as roots
inRootPaths = map[string]bool{}
)
for _, pkg := range pkgs {
if !pkg.fromExternalModule() {
continue
}
if m := pkg.mod; !keptPath[m.Path] {
keep = append(keep, m)
keptPath[m.Path] = true
if direct[m.Path] && !inRootPaths[m.Path] {
rootPaths = append(rootPaths, m.Path)
inRootPaths[m.Path] = true
}
}
}
min, err := mvs.Req(Target, rootPaths, &mvsReqs{roots: keep})
if err != nil {
return nil, err
}
return newRequirements(eager, min, direct), nil
}
// updateEagerRoots returns a set of root requirements that includes the selected
// version of every module path in direct as a root, and maintains the selected
// version of every module selected in the graph of rs.
//
// The roots are updated such that:
//
// 1. The selected version of every module path in direct is included as a root
// (if it is not "none").
// 2. Each root is the selected version of its path. (We say that such a root
// set is “consistent”.)
// 3. Every version selected in the graph of rs remains selected unless upgraded
// by a dependency in add.
// 4. Every version in add is selected at its given version unless upgraded by
// (the dependencies of) an existing root or another module in add.
func updateEagerRoots(ctx context.Context, direct map[string]bool, rs *Requirements, add []module.Version) (*Requirements, error) {
mg, err := rs.Graph(ctx)
if err != nil {
// We can't ignore errors in the module graph even if the user passed the -e
// flag to try to push past them. If we can't load the complete module
// dependencies, then we can't reliably compute a minimal subset of them.
return rs, err
}
if cfg.BuildMod != "mod" {
// Instead of actually updating the requirements, just check that no updates
// are needed.
if rs == nil {
// We're being asked to reconstruct the requirements from scratch,
// but we aren't even allowed to modify them.
return rs, errGoModDirty
}
for _, m := range rs.rootModules {
if m.Version != mg.Selected(m.Path) {
// The root version v is misleading: the actual selected version is higher.
return rs, errGoModDirty
}
}
for _, m := range add {
if m.Version != mg.Selected(m.Path) {
return rs, errGoModDirty
}
}
for mPath := range direct {
if _, ok := rs.rootSelected(mPath); !ok {
// Module m is supposed to be listed explicitly, but isn't.
//
// Note that this condition is also detected (and logged with more
// detail) earlier during package loading, so it shouldn't actually be
// possible at this point — this is just a defense in depth.
return rs, errGoModDirty
}
}
// No explicit roots are missing and all roots are already at the versions
// we want to keep. Any other changes we would make are purely cosmetic,
// such as pruning redundant indirect dependencies. Per issue #34822, we
// ignore cosmetic changes when we cannot update the go.mod file.
return rs, nil
}
var (
rootPaths []string // module paths that should be included as roots
inRootPaths = map[string]bool{}
)
for _, root := range rs.rootModules {
// If the selected version of the root is the same as what was already
// listed in the go.mod file, retain it as a root (even if redundant) to
// avoid unnecessary churn. (See https://golang.org/issue/34822.)
//
// We do this even for indirect requirements, since we don't know why they
// were added and they could become direct at any time.
if !inRootPaths[root.Path] && mg.Selected(root.Path) == root.Version {
rootPaths = append(rootPaths, root.Path)
inRootPaths[root.Path] = true
}
}
// “The selected version of every module path in direct is included as a root.”
//
// This is only for convenience and clarity for end users: in an eager module,
// the choice of explicit vs. implicit dependency has no impact on MVS
// selection (for itself or any other module).
keep := append(mg.BuildList()[1:], add...)
for _, m := range keep {
if direct[m.Path] && !inRootPaths[m.Path] {
rootPaths = append(rootPaths, m.Path)
inRootPaths[m.Path] = true
}
}
min, err := mvs.Req(Target, rootPaths, &mvsReqs{roots: keep})
if err != nil {
return rs, err
}
if rs.depth == eager && reflect.DeepEqual(min, rs.rootModules) && reflect.DeepEqual(direct, rs.direct) {
// The root set is unchanged and rs was already eager, so keep rs to
// preserve its cached ModuleGraph (if any).
return rs, nil
}
return newRequirements(eager, min, direct), nil
}
// convertDepth returns a version of rs with the given depth.
// If rs already has the given depth, convertDepth returns rs unmodified.
func convertDepth(ctx context.Context, rs *Requirements, depth modDepth) (*Requirements, error) {
if rs.depth == depth {
return rs, nil
}
if depth == eager {
// We are converting a lazy module to an eager one. The roots of an eager
// module graph are a superset of the roots of a lazy graph, so we don't
// need to add any new roots — we just need to prune away the ones that are
// redundant given eager loading, which is exactly what updateEagerRoots
// does.
return updateEagerRoots(ctx, rs.direct, rs, nil)
}
// We are converting an eager module to a lazy one. The module graph of an
// eager module includes the transitive dependencies of every module in the
// build list.
//
// Hey, we can express that as a lazy root set! “Include the transitive
// dependencies of every module in the build list” is exactly what happens in
// a lazy module if we promote every module in the build list to a root!
mg, err := rs.Graph(ctx)
if err != nil {
return rs, err
}
return newRequirements(lazy, mg.BuildList()[1:], rs.direct), nil
}
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