1 files changed, 116 insertions, 0 deletions

diff --git a/cli/internal/packagemanager/yarn.go b/cli/internal/packagemanager/yarn.go
new file mode 100644
index 0000000..8779c5f
--- /dev/null
+++ b/cli/internal/packagemanager/yarn.go
@@ -0,0 +1,116 @@
+package packagemanager
+
+import (
+	"errors"
+	"fmt"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"github.com/Masterminds/semver"
+	"github.com/vercel/turbo/cli/internal/fs"
+	"github.com/vercel/turbo/cli/internal/lockfile"
+	"github.com/vercel/turbo/cli/internal/turbopath"
+)
+
+// NoWorkspacesFoundError is a custom error used so that upstream implementations can switch on it
+type NoWorkspacesFoundError struct{}
+
+func (e *NoWorkspacesFoundError) Error() string {
+	return "package.json: no workspaces found. Turborepo requires Yarn workspaces to be defined in the root package.json"
+}
+
+var nodejsYarn = PackageManager{
+	Name:         "nodejs-yarn",
+	Slug:         "yarn",
+	Command:      "yarn",
+	Specfile:     "package.json",
+	Lockfile:     "yarn.lock",
+	PackageDir:   "node_modules",
+	ArgSeparator: []string{"--"},
+
+	getWorkspaceGlobs: func(rootpath turbopath.AbsoluteSystemPath) ([]string, error) {
+		pkg, err := fs.ReadPackageJSON(rootpath.UntypedJoin("package.json"))
+		if err != nil {
+			return nil, fmt.Errorf("package.json: %w", err)
+		}
+		if len(pkg.Workspaces) == 0 {
+			return nil, &NoWorkspacesFoundError{}
+		}
+		return pkg.Workspaces, nil
+	},
+
+	getWorkspaceIgnores: func(pm PackageManager, rootpath turbopath.AbsoluteSystemPath) ([]string, error) {
+		// function: https://github.com/yarnpkg/yarn/blob/3119382885ea373d3c13d6a846de743eca8c914b/src/config.js#L799
+
+		// Yarn is unique in ignore patterns handling.
+		// The only time it does globbing is for package.json or yarn.json and it scopes the search to each workspace.
+		// For example: `apps/*/node_modules/**/+(package.json|yarn.json)`
+		// The `extglob` `+(package.json|yarn.json)` (from micromatch) after node_modules/** is redundant.
+
+		globs, err := pm.getWorkspaceGlobs(rootpath)
+		if err != nil {
+			// In case of a non-monorepo, the workspaces field is empty and only node_modules in the root should be ignored
+			var e *NoWorkspacesFoundError
+			if errors.As(err, &e) {
+				return []string{"node_modules/**"}, nil
+			}
+
+			return nil, err
+		}
+
+		ignores := make([]string, len(globs))
+
+		for i, glob := range globs {
+			ignores[i] = filepath.Join(glob, "/node_modules/**")
+		}
+
+		return ignores, nil
+	},
+
+	canPrune: func(cwd turbopath.AbsoluteSystemPath) (bool, error) {
+		return true, nil
+	},
+
+	// Versions older than 2.0 are yarn, after that they become berry
+	Matches: func(manager string, version string) (bool, error) {
+		if manager != "yarn" {
+			return false, nil
+		}
+
+		v, err := semver.NewVersion(version)
+		if err != nil {
+			return false, fmt.Errorf("could not parse yarn version: %w", err)
+		}
+		c, err := semver.NewConstraint("<2.0.0-0")
+		if err != nil {
+			return false, fmt.Errorf("could not create constraint: %w", err)
+		}
+
+		return c.Check(v), nil
+	},
+
+	// Detect for yarn needs to identify which version of yarn is running on the system.
+	detect: func(projectDirectory turbopath.AbsoluteSystemPath, packageManager *PackageManager) (bool, error) {
+		specfileExists := projectDirectory.UntypedJoin(packageManager.Specfile).FileExists()
+		lockfileExists := projectDirectory.UntypedJoin(packageManager.Lockfile).FileExists()
+
+		// Short-circuit, definitely not Yarn.
+		if !specfileExists || !lockfileExists {
+			return false, nil
+		}
+
+		cmd := exec.Command("yarn", "--version")
+		cmd.Dir = projectDirectory.ToString()
+		out, err := cmd.Output()
+		if err != nil {
+			return false, fmt.Errorf("could not detect yarn version: %w", err)
+		}
+
+		return packageManager.Matches(packageManager.Slug, strings.TrimSpace(string(out)))
+	},
+
+	UnmarshalLockfile: func(_rootPackageJSON *fs.PackageJSON, contents []byte) (lockfile.Lockfile, error) {
+		return lockfile.DecodeYarnLockfile(contents)
+	},
+}