cmd/go/internal/modload: remove (*loader).forceStdVendor

forceStdVendor was a special-case mechanism to allow Go contributors
to use vendored dependencies by default when working in GOROOT/src.

As of Go 1.14,¹ the 'go' command uses vendored dependencies by default
within all modules, so the 'std' and 'cmd' modules no longer need to
be special cases, and we can remove this special-case code.

¹ https://golang.org/doc/go1.14#vendor

Updates #33848
Updates #30241

Change-Id: Ib2fb5841c253113b17fa86a086ce85a22ac3d121
Reviewed-on: https://go-review.googlesource.com/c/go/+/251159
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>

3 files changed, 57 insertions, 38 deletions

diff --git a/src/cmd/go/internal/modload/load.go b/src/cmd/go/internal/modload/load.go
index 64ef60230e..8a3af534a5 100644
--- a/src/cmd/go/internal/modload/load.go
+++ b/src/cmd/go/internal/modload/load.go
@@ -709,8 +709,6 @@ func Lookup(parentPath string, parentIsStd bool, path string) (dir, realPath str
 type loader struct {
 	loaderParams
 
-	forceStdVendor bool // if true, load standard-library dependencies from the vendor subtree
-
 	work *par.Queue
 
 	// reset on each iteration
@@ -850,13 +848,6 @@ func loadFromRoots(params loaderParams) *loader {
 		work:         par.NewQueue(runtime.GOMAXPROCS(0)),
 	}
 
-	// Inside the "std" and "cmd" modules, we prefer to use the vendor directory
-	// unless the command explicitly changes the module graph.
-	// TODO(bcmills): Is this still needed now that we have automatic vendoring?
-	if !targetInGorootSrc || (cfg.CmdName != "get" && !strings.HasPrefix(cfg.CmdName, "mod ")) {
-		ld.forceStdVendor = true
-	}
-
 	var err error
 	reqs := Reqs()
 	buildList, err = mvs.BuildList(Target, reqs)
@@ -1120,8 +1111,8 @@ func (ld *loader) load(pkg *loadPkg) {
 	}
 	for _, path := range imports {
 		if pkg.inStd {
-			// Imports from packages in "std" should resolve using GOROOT/src/vendor
-			// even when "std" is not the main module.
+			// Imports from packages in "std" and "cmd" should resolve using
+			// GOROOT/src/vendor even when "std" is not the main module.
 			path = ld.stdVendor(pkg.path, path)
 		}
 		pkg.imports = append(pkg.imports, ld.pkg(path, importFlags))
@@ -1185,13 +1176,21 @@ func (ld *loader) stdVendor(parentPath, path string) string {
 	}
 
 	if str.HasPathPrefix(parentPath, "cmd") {
-		if ld.forceStdVendor || Target.Path != "cmd" {
+		if Target.Path != "cmd" {
 			vendorPath := pathpkg.Join("cmd", "vendor", path)
 			if _, err := os.Stat(filepath.Join(cfg.GOROOTsrc, filepath.FromSlash(vendorPath))); err == nil {
 				return vendorPath
 			}
 		}
-	} else if ld.forceStdVendor || Target.Path != "std" {
+	} else if Target.Path != "std" || str.HasPathPrefix(parentPath, "vendor") {
+		// If we are outside of the 'std' module, resolve imports from within 'std'
+		// to the vendor directory.
+		//
+		// Do the same for importers beginning with the prefix 'vendor/' even if we
+		// are *inside* of the 'std' module: the 'vendor/' packages that resolve
+		// globally from GOROOT/src/vendor (and are listed as part of 'go list std')
+		// are distinct from the real module dependencies, and cannot import internal
+		// packages from the real module.
 		vendorPath := pathpkg.Join("vendor", path)
 		if _, err := os.Stat(filepath.Join(cfg.GOROOTsrc, filepath.FromSlash(vendorPath))); err == nil {
 			return vendorPath
diff --git a/src/cmd/go/testdata/script/mod_list_std.txt b/src/cmd/go/testdata/script/mod_list_std.txt
index 76a3b00d1c..baf7908ab9 100644
--- a/src/cmd/go/testdata/script/mod_list_std.txt
+++ b/src/cmd/go/testdata/script/mod_list_std.txt
@@ -6,8 +6,13 @@ env GOPROXY=off
 
 # Outside of GOROOT, our vendored packages should be reported as part of the standard library.
 go list -f '{{if .Standard}}{{.ImportPath}}{{end}}' std cmd
-stdout ^vendor/golang.org/x/net/http2/hpack
+stdout ^vendor/golang\.org/x/net/http2/hpack
 stdout ^cmd/vendor/golang\.org/x/arch/x86/x86asm
+! stdout ^golang\.org/x/
+
+# The dependencies of those packages should also be vendored.
+go list -deps vendor/golang.org/x/crypto/chacha20
+stdout ^vendor/golang\.org/x/crypto/internal/subtle
 
 # cmd/... should match the same packages it used to match in GOPATH mode.
 go list cmd/...
@@ -23,40 +28,57 @@ stdout ^bytes$
 ! stdout ^builtin$
 ! stdout ^cmd/
 ! stdout ^vendor/
+! stdout ^golang\.org/x/
+
 
+# Vendored dependencies should appear with their 'vendor/' paths in std (they're
+# in GOROOT/src, but not in the 'std' module following the usual module-boundary
+# rules).
 
-# Within the std module, listing ./... should omit the 'std' prefix:
-# the package paths should be the same via ./... or the 'std' meta-pattern.
-# TODO(golang.org/issue/30241): Make that work.
-# Today, they are listed in 'std' but not './...'.
 cd $GOROOT/src
-go list ./...
-! stdout ^vendor/golang.org/x  # TODO: should be included, or should be omitted from 'std'.
 
-cp stdout $WORK/listdot.txt
 go list std
-stdout ^vendor/golang.org/x  # TODO: remove vendor/ prefix
-# TODO: cmp stdout $WORK/listdot.txt
+stdout ^vendor/golang.org/x/net/http2/hpack
+! stdout ^golang\.org/x
+
+# The dependencies of packages with an explicit 'vendor/' prefix should
+# still themselves resolve to vendored packages.
+go list -deps vendor/golang.org/x/crypto/chacha20
+stdout ^vendor/golang.org/x/crypto/internal/subtle
+! stdout ^golang\.org/x
+
+# Within the std module, the dependencies of the non-vendored packages within
+# std should appear to come from modules, but they should be loaded from the
+# vendor directory (just like ordinary vendored module dependencies).
 
 go list all
-stdout ^vendor/golang.org/x  # TODO: remove vendor/ prefix.
+stdout ^golang.org/x/
 ! stdout ^std/
+! stdout ^cmd/
+! stdout ^vendor/
 
+go list -deps -f '{{if not .Standard}}{{.ImportPath}}{{end}}' std
+! stdout ^vendor/golang.org/x/net/http2/hpack
+stdout ^golang.org/x/net/http2/hpack
 
-# Within the std module, the vendored dependencies of std should appear
-# to come from the actual modules.
-# TODO(golang.org/issue/30241): Make that work.
-# Today, they still have the vendor/ prefix.
-go list std
-stdout ^vendor/golang.org/x/net/http2/hpack  # TODO
-! stdout ^golang.org/x/net/http2/hpack       # TODO
+go list -f '{{.Dir}}' golang.org/x/net/http2/hpack
+stdout $GOROOT[/\\]src[/\\]vendor
 
-go list -deps -f '{{if not .Standard}}{{.ImportPath}}{{end}}' std
-# ! stdout ^vendor/golang.org/x/net/http2/hpack  # TODO
-! stdout ^golang.org/x/net/http2/hpack         # TODO
+# Within the std module, the packages within the module should omit the 'std/'
+# prefix (they retain their own identities), but should respect normal module
+# boundaries (vendored packages are not included in the module, even though they
+# are included in the 'std' pattern).
+
+go list ./...
+stdout ^bytes$
+! stdout ^builtin$
+! stdout ^cmd/
+! stdout ^vendor/
+! stdout ^golang\.org/x/
 
 
 # Within std, the vendored dependencies of cmd should still appear to be part of cmd.
+
 go list -f '{{if .Standard}}{{.ImportPath}}{{end}}' cmd
 stdout ^cmd/vendor/golang\.org/x/arch/x86/x86asm
 
diff --git a/src/cmd/go/testdata/script/mod_std_vendor.txt b/src/cmd/go/testdata/script/mod_std_vendor.txt
index 5986cff594..fb954d74ed 100644
--- a/src/cmd/go/testdata/script/mod_std_vendor.txt
+++ b/src/cmd/go/testdata/script/mod_std_vendor.txt
@@ -37,12 +37,10 @@ stderr 'use of vendored package'
 
 # When run within the 'std' module, 'go list -test' should report vendored
 # transitive dependencies at their original module paths.
-# TODO(golang.org/issue/30241): Make that work.
-# Today, they're standard packages as long as they exist.
 cd $GOROOT/src
 go list -test -f '{{range .Deps}}{{.}}{{"\n"}}{{end}}' net/http
-stdout ^vendor/golang.org/x/net/http2/hpack  # TODO: remove vendor/ prefix
-! stdout ^golang.org/x/net/http2/hpack
+stdout ^golang.org/x/net/http2/hpack
+! stdout ^vendor/golang.org/x/net/http2/hpack
 
 -- go.mod --
 module m