cmd/go/internal/modconv: use modules to examine instead of using only direct source control entries

Since modules now support parsing multiple forms of versions (including
commit hash and source control tag), I think modconv.ConvertLegacyConfig
no longer needs modfetch.ImportRepoRev. So I suggest that we use modules
to convert legacy config instead of using VCS directly. By doing this,
we can make the module proxy participate in the conversion process and
benefit from it (such as speeding up "go mod init" or breaking through
the firewall).

And since modconv.ConvertLegacyConfig is the only caller of
modfetch.ImportRepoRev, I think modfetch.ImportRepoRev can be removed.

Fixes #33767

Change-Id: Ic79b14fa805ed297ca1735a8498cfed2a5ddeec2
Reviewed-on: https://go-review.googlesource.com/c/go/+/191218
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/cmd/go/internal/modconv/convert.go

@@ -66,16 +66,19 @@ func ConvertLegacyConfig(f *modfile.File, file string, data []byte) error {
 
 	work.Do(10, func(item interface{}) {
 		r := item.(module.Version)
-		repo, info, err := modfetch.ImportRepoRev(r.Path, r.Version)
+		var info *modfetch.RevInfo
+		err := modfetch.TryProxies(func(proxy string) (err error) {
+			info, err = modfetch.Stat(proxy, r.Path, r.Version)
+			return err
+		})
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "go: converting %s: stat %s@%s: %v\n", base.ShortPath(file), r.Path, r.Version, err)
 			return
 		}
 		mu.Lock()
-		path := repo.ModulePath()
 		// Don't use semver.Max here; need to preserve +incompatible suffix.
-		if v, ok := need[path]; !ok || semver.Compare(v, info.Version) < 0 {
-			need[path] = info.Version
+		if v, ok := need[r.Path]; !ok || semver.Compare(v, info.Version) < 0 {
+			need[r.Path] = info.Version
 		}
 		mu.Unlock()
 	})

src/cmd/go/internal/modfetch/repo.go

@@ -161,15 +161,6 @@ type RevInfo struct {
 // and it can check that the path can be resolved to a target repository.
 // To avoid version control access except when absolutely necessary,
 // Lookup does not attempt to connect to the repository itself.
-//
-// The ImportRepoRev function is a variant of Import which is limited
-// to code in a source code repository at a particular revision identifier
-// (usually a commit hash or source code repository tag, not necessarily
-// a module version).
-// ImportRepoRev is used when converting legacy dependency requirements
-// from older systems into go.mod files. Those older systems worked
-// at either package or repository granularity, and most of the time they
-// recorded commit hashes, not tagged versions.
 
 var lookupCache par.Cache
 
@@ -279,53 +270,6 @@ func lookupCodeRepo(rr *get.RepoRoot) (codehost.Repo, error) {
 	return code, nil
 }
 
-// ImportRepoRev returns the module and version to use to access
-// the given import path loaded from the source code repository that
-// the original "go get" would have used, at the specific repository revision
-// (typically a commit hash, but possibly also a source control tag).
-func ImportRepoRev(path, rev string) (Repo, *RevInfo, error) {
-	if cfg.BuildMod == "vendor" || cfg.BuildMod == "readonly" {
-		return nil, nil, fmt.Errorf("repo version lookup disabled by -mod=%s", cfg.BuildMod)
-	}
-
-	// Note: Because we are converting a code reference from a legacy
-	// version control system, we ignore meta tags about modules
-	// and use only direct source control entries (get.IgnoreMod).
-	security := web.SecureOnly
-	if get.Insecure {
-		security = web.Insecure
-	}
-	rr, err := get.RepoRootForImportPath(path, get.IgnoreMod, security)
-	if err != nil {
-		return nil, nil, err
-	}
-
-	code, err := lookupCodeRepo(rr)
-	if err != nil {
-		return nil, nil, err
-	}
-
-	revInfo, err := code.Stat(rev)
-	if err != nil {
-		return nil, nil, err
-	}
-
-	// TODO: Look in repo to find path, check for go.mod files.
-	// For now we're just assuming rr.Root is the module path,
-	// which is true in the absence of go.mod files.
-
-	repo, err := newCodeRepo(code, rr.Root, rr.Root)
-	if err != nil {
-		return nil, nil, err
-	}
-
-	info, err := repo.(*codeRepo).convert(revInfo, rev)
-	if err != nil {
-		return nil, nil, err
-	}
-	return repo, info, nil
-}
-
 func SortVersions(list []string) {
 	sort.Slice(list, func(i, j int) bool {
 		cmp := semver.Compare(list[i], list[j])

src/cmd/go/testdata/script/mod_init_dep.txt

 env GO111MODULE=on
 
-# modconv uses git directly to examine what old 'go get' would
-[!net] skip
-[!exec:git] skip
+# modconv uses modules to examine instead of using git directly
+[short] skip
 
 # go build should populate go.mod from Gopkg.lock
 cp go.mod1 go.mod
 go build
 stderr 'copying requirements from Gopkg.lock'
+stderr 'finding rsc.io/sampler v1.0.0'
 go list -m all
 ! stderr 'copying requirements from Gopkg.lock'
+! stderr 'finding rsc.io/sampler v1.0.0'
 stdout 'rsc.io/sampler v1.0.0'
 
 # go list should populate go.mod from Gopkg.lock
 cp go.mod1 go.mod
 go list
 stderr 'copying requirements from Gopkg.lock'
+! stderr 'finding rsc.io/sampler v1.0.0'
 go list
 ! stderr 'copying requirements from Gopkg.lock'
+! stderr 'finding rsc.io/sampler v1.0.0'
 go list -m all
 stdout 'rsc.io/sampler v1.0.0'
 
@@ -54,4 +57,4 @@ go $goversion
 
 replace z v1.0.0 => rsc.io/quote v1.0.0
 
-require rsc.io/quote v1.0.0
+require rsc.io/quote v1.0.0
\ No newline at end of file