cmd/go/internal/modload: add a "v" prefix to the indexed go version

This allows semver-based comparisons of the version without additional allocations.

Also comment on the reason for the loops that iterate over modFile instead.

(I was reading the vendor code in order to add the lazy-loading version check,
and this section was a bit unclear to me.)

For #36460

Change-Id: I11559d81ffb4eba0e4e10e6fa3c01990b11f9180
Reviewed-on: https://go-review.googlesource.com/c/go/+/240622
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Michael Matloob <matloob@golang.org>

diff --git a/src/cmd/go/internal/modload/init.go b/src/cmd/go/internal/modload/init.go
index 93027c44c41aa5a6dbc32c3fd3cabc55508fda00..71c7b158b8169b28e7fc99a035359935a3ed94ac 100644 (file)
--- a/src/cmd/go/internal/modload/init.go
+++ b/src/cmd/go/internal/modload/init.go
@@ -483,15 +483,15 @@ func setDefaultBuildMod() {
 
        if fi, err := os.Stat(filepath.Join(modRoot, "vendor")); err == nil && fi.IsDir() {
                modGo := "unspecified"
-               if index.goVersion != "" {
-                       if semver.Compare("v"+index.goVersion, "v1.14") >= 0 {
+               if index.goVersionV != "" {
+                       if semver.Compare(index.goVersionV, "v1.14") >= 0 {
                                // The Go version is at least 1.14, and a vendor directory exists.
                                // Set -mod=vendor by default.
                                cfg.BuildMod = "vendor"
                                cfg.BuildModReason = "Go version in go.mod is at least 1.14 and vendor directory exists."
                                return
                        } else {
-                               modGo = index.goVersion
+                               modGo = index.goVersionV[1:]
                        }
                }
 

diff --git a/src/cmd/go/internal/modload/modfile.go b/src/cmd/go/internal/modload/modfile.go
index 9f4ec5a49fcca9e368aefc9a4b62e30201493517..9a166cae541c3086e6d0c64cfbbf08b1afb2febb 100644 (file)
--- a/src/cmd/go/internal/modload/modfile.go
+++ b/src/cmd/go/internal/modload/modfile.go
@@ -20,7 +20,7 @@ type modFileIndex struct {
        data         []byte
        dataNeedsFix bool // true if fixVersion applied a change while parsing data
        module       module.Version
-       goVersion    string
+       goVersionV   string // GoVersion with "v" prefix
        require      map[module.Version]requireMeta
        replace      map[module.Version]module.Version
        exclude      map[module.Version]bool
@@ -66,9 +66,11 @@ func indexModFile(data []byte, modFile *modfile.File, needsFix bool) *modFileInd
                i.module = modFile.Module.Mod
        }
 
-       i.goVersion = ""
+       i.goVersionV = ""
        if modFile.Go != nil {
-               i.goVersion = modFile.Go.Version
+               // We're going to use the semver package to compare Go versions, so go ahead
+               // and add the "v" prefix it expects once instead of every time.
+               i.goVersionV = "v" + modFile.Go.Version
        }
 
        i.require = make(map[module.Version]requireMeta, len(modFile.Require))
@@ -114,11 +116,11 @@ func (i *modFileIndex) modFileIsDirty(modFile *modfile.File) bool {
        }
 
        if modFile.Go == nil {
-               if i.goVersion != "" {
+               if i.goVersionV != "" {
                        return true
                }
-       } else if modFile.Go.Version != i.goVersion {
-               if i.goVersion == "" && cfg.BuildMod == "readonly" {
+       } else if "v"+modFile.Go.Version != i.goVersionV {
+               if i.goVersionV == "" && cfg.BuildMod == "readonly" {
                        // go.mod files did not always require a 'go' version, so do not error out
                        // if one is missing — we may be inside an older module in the module
                        // cache, and should bias toward providing useful behavior.

diff --git a/src/cmd/go/internal/modload/vendor.go b/src/cmd/go/internal/modload/vendor.go
index 71f68efbcc13dacbd0c23a5d6fb8f5094f6bba21..9f34b829fc2d90e6de352e379cbbb4baaada11c8 100644 (file)
--- a/src/cmd/go/internal/modload/vendor.go
+++ b/src/cmd/go/internal/modload/vendor.go
@@ -133,7 +133,7 @@ func checkVendorConsistency() {
        readVendorList()
 
        pre114 := false
-       if modFile.Go == nil || semver.Compare("v"+modFile.Go.Version, "v1.14") < 0 {
+       if semver.Compare(index.goVersionV, "v1.14") < 0 {
                // Go versions before 1.14 did not include enough information in
                // vendor/modules.txt to check for consistency.
                // If we know that we're on an earlier version, relax the consistency check.
@@ -150,6 +150,8 @@ func checkVendorConsistency() {
                }
        }
 
+       // Iterate over the Require directives in their original (not indexed) order
+       // so that the errors match the original file.
        for _, r := range modFile.Require {
                if !vendorMeta[r.Mod].Explicit {
                        if pre114 {