fix: no longer crash for single projects with global dependencies (#5002

)

### Description

Fixes #4914, this is the pnpm implementation of #4240

Was caused as `pnpm` when calculating ignores touches the file system
and will error if `pnpm-workspace.yaml` isn't present. This also avoids
failing on the rare case of someone using turbo on a single project with
no external dependencies as pnpm won't create a lockfile in this case.

### Testing Instructions

Added integration test for a single project using pnpm with global
dependencies

---------

Co-authored-by: Chris Olszewski <Chris Olszewski>

cli/internal/packagemanager/pnpm.go

@@ -1,7 +1,9 @@
 package packagemanager
 
 import (
+	"errors"
 	"fmt"
+	stdfs "io/fs"
 	"strings"
 
 	"github.com/vercel/turbo/cli/internal/fs"
@@ -58,6 +60,10 @@ func getPnpmWorkspaceIgnores(pm PackageManager, rootpath turbopath.AbsoluteSyste
 	}
 	pkgGlobs, err := readPnpmWorkspacePackages(rootpath.UntypedJoin("pnpm-workspace.yaml"))
 	if err != nil {
+		// If workspace file doesn't exist we shouldn't error as we might be a single package repo
+		if errors.Is(err, stdfs.ErrNotExist) {
+			return ignores, nil
+		}
 		return nil, err
 	}
 	for _, pkgGlob := range pkgGlobs {

cli/internal/run/global_hash.go

@@ -129,7 +129,9 @@ func getGlobalHashInputs(
 	if lockFile == nil {
 		// If we don't have lockfile information available, add the specfile and lockfile to global deps
 		globalDeps.Add(filepath.Join(rootpath.ToStringDuringMigration(), packageManager.Specfile))
-		globalDeps.Add(filepath.Join(rootpath.ToStringDuringMigration(), packageManager.Lockfile))
+		if rootpath.UntypedJoin(packageManager.Lockfile).Exists() {
+			globalDeps.Add(filepath.Join(rootpath.ToStringDuringMigration(), packageManager.Lockfile))
+		}
 	}
 
 	// No prefix, global deps already have full paths

turborepo-tests/integration/tests/single_package/dry-run-pnpm.t

@@ -0,0 +1,6 @@
+Setup
+  $ . ${TESTDIR}/../../../helpers/setup.sh
+  $ . ${TESTDIR}/../_helpers/setup_monorepo.sh $(pwd) single_package pnpm@8.0.0
+
+We only care about this running sucessfully and not the json output
+  $ ${TURBO} run build --dry=json > /dev/null