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cmd/go/internal/modget: split resolveCandidates into two methods

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It turns out that the existing call sites of the resolveCandidates
method pass only *either* a slice of queries or a slice of upgrades
(never both), and the behaviors triggered by the two parameters don't
overlap much at all. To clarify the two different operations, split
them into two separate methods.

For #36460

Change-Id: I64651637734fd44fea68740a3cdfbacfb73c19b6
Reviewed-on: https://go-review.googlesource.com/c/go/+/289697
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
This commit is contained in:
Bryan C. Mills 2021-02-04 09:42:48 -05:00
parent 5f2e24efb3
commit 4da0188c6c
1 changed files with 60 additions and 46 deletions
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106
src/cmd/go/internal/modget/get.go
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@ -310,7 +310,7 @@ func runGet(ctx context.Context, cmd *base.Command, args []string) {
r.performWildcardQueries(ctx)
r.performPatternAllQueries(ctx)
if changed := r.resolveCandidates(ctx, queries, nil); changed {
if changed := r.resolveQueries(ctx, queries); changed {
// 'go get' arguments can be (and often are) package patterns rather than
// (just) modules. A package can be provided by any module with a prefix
// of its import path, and a wildcard can even match packages in modules
@ -347,12 +347,12 @@ func runGet(ctx context.Context, cmd *base.Command, args []string) {
// - ambiguous import errors.
// TODO(#27899): Try to resolve ambiguous import errors automatically.
upgrades := r.findAndUpgradeImports(ctx, queries)
if changed := r.resolveCandidates(ctx, nil, upgrades); changed {
if changed := r.applyUpgrades(ctx, upgrades); changed {
continue
}
r.findMissingWildcards(ctx)
if changed := r.resolveCandidates(ctx, r.wildcardQueries, nil); changed {
if changed := r.resolveQueries(ctx, r.wildcardQueries); changed {
continue
}
@ -460,9 +460,8 @@ type resolver struct {
// that resolved the module to that version (the “reason”).
resolvedVersion map[string]versionReason
buildList []module.Version
buildListResolvedVersions int // len(resolvedVersion) when buildList was computed
buildListVersion map[string]string // index of buildList (module path → version)
buildList []module.Version
buildListVersion map[string]string // index of buildList (module path → version)
initialVersion map[string]string // index of the initial build list at the start of 'go get'
@ -1176,24 +1175,19 @@ func (r *resolver) loadPackages(ctx context.Context, patterns []string, findPack
// to be updated before its dependencies can be loaded.
var errVersionChange = errors.New("version change needed")
// resolveCandidates resolves candidates sets that are attached to the given
// resolveQueries resolves candidate sets that are attached to the given
// queries and/or needed to provide the given missing-package dependencies.
//
// resolveCandidates starts by resolving one module version from each
// resolveQueries starts by resolving one module version from each
// unambiguous pathSet attached to the given queries.
//
// If no unambiguous query results in a change to the build list,
// resolveCandidates modifies the build list by adding one module version from
// each pathSet in missing, but does not mark those versions as resolved
// (so they can still be modified by other queries).
//
// If that still does not result in any changes to the build list,
// resolveCandidates revisits the ambiguous query candidates and resolves them
// resolveQueries revisits the ambiguous query candidates and resolves them
// arbitrarily in order to guarantee forward progress.
//
// If all pathSets are resolved without any changes to the build list,
// resolveCandidates returns with changed=false.
func (r *resolver) resolveCandidates(ctx context.Context, queries []*query, upgrades []pathSet) (changed bool) {
// resolveQueries returns with changed=false.
func (r *resolver) resolveQueries(ctx context.Context, queries []*query) (changed bool) {
defer base.ExitIfErrors()
// Note: this is O(N²) with the number of pathSets in the worst case.
@ -1247,13 +1241,53 @@ func (r *resolver) resolveCandidates(ctx context.Context, queries []*query, upgr
}
}
if changed := r.updateBuildList(ctx, nil); changed {
// The build list has changed, so disregard any missing packages: they might
// now be determined by requirements in the build list, which we would
// prefer to use instead of arbitrary "latest" versions.
return true
if resolved > 0 {
if changed = r.updateBuildList(ctx, nil); changed {
// The build list has changed, so disregard any remaining ambiguous queries:
// they might now be determined by requirements in the build list, which we
// would prefer to use instead of arbitrary versions.
return true
}
}
// The build list will be the same on the next iteration as it was on this
// iteration, so any ambiguous queries will remain so. In order to make
// progress, resolve them arbitrarily but deterministically.
//
// If that results in conflicting versions, the user can re-run 'go get'
// with additional explicit versions for the conflicting packages or
// modules.
resolvedArbitrarily := 0
for _, q := range queries {
for _, cs := range q.candidates {
isPackage, m := r.chooseArbitrarily(cs)
if isPackage {
q.matchesPackages = true
}
r.resolve(q, m)
resolvedArbitrarily++
}
}
if resolvedArbitrarily > 0 {
changed = r.updateBuildList(ctx, nil)
}
return changed
}
// applyUpgrades disambiguates candidate sets that are needed to upgrade (or
// provide) transitive dependencies imported by previously-resolved packages.
//
// applyUpgrades modifies the build list by adding one module version from each
// pathSet in upgrades, then downgrading (or further upgrading) those modules as
// needed to maintain any already-resolved versions of other modules.
// applyUpgrades does not mark the new versions as resolved, so they can still
// be further modified by other queries (such as wildcards).
//
// If all pathSets are resolved without any changes to the build list,
// applyUpgrades returns with changed=false.
func (r *resolver) applyUpgrades(ctx context.Context, upgrades []pathSet) (changed bool) {
defer base.ExitIfErrors()
// Arbitrarily add a "latest" version that provides each missing package, but
// do not mark the version as resolved: we still want to allow the explicit
// queries to modify the resulting versions.
@ -1276,27 +1310,9 @@ func (r *resolver) resolveCandidates(ctx context.Context, queries []*query, upgr
tentative = append(tentative, m)
}
base.ExitIfErrors()
if changed := r.updateBuildList(ctx, tentative); changed {
return true
}
// The build list will be the same on the next iteration as it was on this
// iteration, so any ambiguous queries will remain so. In order to make
// progress, resolve them arbitrarily but deterministically.
//
// If that results in conflicting versions, the user can re-run 'go get'
// with additional explicit versions for the conflicting packages or
// modules.
for _, q := range queries {
for _, cs := range q.candidates {
isPackage, m := r.chooseArbitrarily(cs)
if isPackage {
q.matchesPackages = true
}
r.resolve(q, m)
}
}
return r.updateBuildList(ctx, nil)
changed = r.updateBuildList(ctx, tentative)
return changed
}
// disambiguate eliminates candidates from cs that conflict with other module
@ -1614,11 +1630,10 @@ func (r *resolver) resolve(q *query, m module.Version) {
//
// If the additional modules conflict with the resolved versions, they will be
// downgraded to a non-conflicting version (possibly "none").
//
// If the resulting build list is the same as the one resulting from the last
// call to updateBuildList, updateBuildList returns with changed=false.
func (r *resolver) updateBuildList(ctx context.Context, additions []module.Version) (changed bool) {
if len(additions) == 0 && len(r.resolvedVersion) == r.buildListResolvedVersions {
return false
}
defer base.ExitIfErrors()
resolved := make([]module.Version, 0, len(r.resolvedVersion))
@ -1649,7 +1664,6 @@ func (r *resolver) updateBuildList(ctx context.Context, additions []module.Versi
}
buildList := modload.LoadAllModules(ctx)
r.buildListResolvedVersions = len(r.resolvedVersion)
if reflect.DeepEqual(r.buildList, buildList) {
return false
}