internal/lsp: handle major versions above v0/v1 in workspace module mode

Workspace mode did not yet support major versions other than v0/v1. To
do so, we have to check the major version before creating the fake gopls
workspace pseudoversion that goes in the workspace module.

Fixes golang/go#41807

Change-Id: I108fe504fdf9e9a0ce23f7102991c9ae78f12a9f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/260004
Trust: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>

gopls/internal/regtest/workspace_test.go

@@ -455,3 +455,59 @@ var _ = fmt.Printf
 		env.GoToDefinition("/tmp/foo.go", env.RegexpSearch("/tmp/foo.go", `Printf`))
 	})
 }
+
+func TestMultiModuleV2(t *testing.T) {
+	const multiModule = `
+-- moda/a/go.mod --
+module a.com
+
+require b.com/v2 v2.0.0
+-- moda/a/a.go --
+package a
+
+import (
+	"b.com/v2/b"
+)
+
+func main() {
+	var x int
+	_ = b.Hi()
+}
+-- modb/go.mod --
+module b.com
+
+-- modb/b/b.go --
+package b
+
+func Hello() int {
+	var x int
+}
+-- modb/v2/go.mod --
+module b.com/v2
+
+-- modb/v2/b/b.go --
+package b
+
+func Hi() int {
+	var x int
+}
+-- modc/go.mod --
+module gopkg.in/yaml.v1 // test gopkg.in versions
+-- modc/main.go --
+package main
+
+func main() {
+	var x int
+}
+`
+	withOptions(
+		WithModes(Experimental),
+	).run(t, multiModule, func(t *testing.T, env *Env) {
+		env.Await(
+			env.DiagnosticAtRegexp("moda/a/a.go", "x"),
+			env.DiagnosticAtRegexp("modb/b/b.go", "x"),
+			env.DiagnosticAtRegexp("modb/v2/b/b.go", "x"),
+			env.DiagnosticAtRegexp("modc/main.go", "x"),
+		)
+	})
+}

internal/lsp/cache/check.go

@@ -278,7 +278,7 @@ func typeCheck(ctx context.Context, snapshot *snapshot, m *metadata, mode source
 	// meaningless, and we don't want clients to access it.
 	if m.module != nil {
 		version := m.module.Version
-		if version == source.WorkspaceModuleVersion {
+		if source.IsWorkspaceModuleVersion(version) {
 			version = ""
 		}
 		pkg.version = &module.Version{

internal/lsp/cache/snapshot.go

@@ -20,6 +20,7 @@ import (
 	"sync"
 
 	"golang.org/x/mod/modfile"
+	"golang.org/x/mod/module"
 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/packages"
 	"golang.org/x/tools/internal/event"
@@ -1545,7 +1546,14 @@ func (s *snapshot) BuildWorkspaceModFile(ctx context.Context) (*modfile.File, er
 		}
 		path := parsed.File.Module.Mod.Path
 		paths[path] = mod
-		file.AddNewRequire(path, source.WorkspaceModuleVersion, false)
+		// If the module's path includes a major version, we expect it to have
+		// a matching major version.
+		_, majorVersion, _ := module.SplitPathVersion(path)
+		if majorVersion == "" {
+			majorVersion = "/v0"
+		}
+		majorVersion = strings.TrimLeft(majorVersion, "/.") // handle gopkg.in versions
+		file.AddNewRequire(path, source.WorkspaceModuleVersion(majorVersion), false)
 		if err := file.AddReplace(path, "", mod.rootURI.Filename(), ""); err != nil {
 			return nil, err
 		}

internal/lsp/mod/diagnostics.go

@@ -88,7 +88,7 @@ func ExtractGoCommandError(ctx context.Context, snapshot source.Snapshot, fh sou
 		path, version := match[1], match[2]
 		// Any module versions that come from the workspace module should not
 		// be shown to the user.
-		if version == source.WorkspaceModuleVersion {
+		if source.IsWorkspaceModuleVersion(version) {
 			continue
 		}
 		if err := module.Check(path, version); err != nil {

internal/lsp/source/view.go

@@ -548,8 +548,17 @@ var (
 	PackagesLoadError     = errors.New("packages.Load error")
 )
 
-// WorkspaceModuleVersion is the nonexistent pseudoversion used in the
+// WorkspaceModuleVersion is the nonexistent pseudoversion suffix used in the
 // construction of the workspace module. It is exported so that we can make
 // sure not to show this version to end users in error messages, to avoid
 // confusion.
-const WorkspaceModuleVersion = "v0.0.0-goplsworkspace"
+// The major version is not included, as that depends on the module path.
+const workspaceModuleVersion = ".0.0-goplsworkspace"
+
+func IsWorkspaceModuleVersion(version string) bool {
+	return strings.HasSuffix(version, workspaceModuleVersion)
+}
+
+func WorkspaceModuleVersion(majorVersion string) string {
+	return majorVersion + workspaceModuleVersion
+}