From: Bryan C. Mills <bcmills@google.com>
Date: Thu, 13 Jul 2023 14:12:33 +0000 (-0400)
Subject: cmd/go/internal/modfetch: always allow Stat for the current toolchain to succeed
X-Git-Tag: go1.21rc3~1^2
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=b88bd917b8dd8aabc471b1de41b3ee8c0d6eeabe;p=gostls13.git

cmd/go/internal/modfetch: always allow Stat for the current toolchain to succeed

This fixes a failure mode observed in TestScript/gotoolchain_version
when building go1.21rc3.

Updates #61259.

Change-Id: Ifb14a5b94b687adea7a26c1155591e3ae75b7a62
Reviewed-on: https://go-review.googlesource.com/c/go/+/509217
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
---

diff --git a/src/cmd/go/internal/modfetch/toolchain.go b/src/cmd/go/internal/modfetch/toolchain.go
index 1669ab92e7..0d7cfcfe7d 100644
--- a/src/cmd/go/internal/modfetch/toolchain.go
+++ b/src/cmd/go/internal/modfetch/toolchain.go
@@ -98,13 +98,23 @@ func (r *toolchainRepo) Stat(ctx context.Context, rev string) (*RevInfo, error)
 	if !gover.IsValid(v) {
 		return nil, fmt.Errorf("invalid %s version %s", r.path, rev)
 	}
+
 	// If we're asking about "go" (not "toolchain"), pretend to have
 	// all earlier Go versions available without network access:
 	// we will provide those ourselves, at least in GOTOOLCHAIN=auto mode.
 	if r.path == "go" && gover.Compare(v, gover.Local()) <= 0 {
 		return &RevInfo{Version: prefix + v}, nil
 	}
+
+	// Similarly, if we're asking about *exactly* the current toolchain,
+	// we don't need to access the network to know that it exists.
+	if r.path == "toolchain" && v == gover.Local() {
+		return &RevInfo{Version: prefix + v}, nil
+	}
+
 	if gover.IsLang(v) {
+		// We can only use a language (development) version if the current toolchain
+		// implements that version, and the two checks above have ruled that out.
 		return nil, fmt.Errorf("go language version %s is not a toolchain version", rev)
 	}