fix dep silently failing

cmd/dep/ensure.go

@@ -9,6 +9,7 @@ import (
 	"encoding/hex"
 	"flag"
 	"fmt"
+	"go/build"
 	"log"
 	"os"
 	"path/filepath"
@@ -128,6 +129,10 @@ func (cmd *ensureCommand) Run(ctx *dep.Ctx, args []string) error {
 		return errors.Wrap(err, "ensure ListPackage for project")
 	}
 
+	if err := checkErrors(params.RootPackageTree.Packages); err != nil {
+		return err
+	}
+
 	if cmd.update {
 		applyUpdateArgs(args, &params)
 	} else {
@@ -362,3 +367,30 @@ func deduceConstraint(s string) gps.Constraint {
 	// TODO: if there is amgibuity here, then prompt the user?
 	return gps.NewVersion(s)
 }
+
+func checkErrors(m map[string]gps.PackageOrErr) error {
+	noGoErrors, pkgErrors := 0, 0
+	for _, poe := range m {
+		if poe.Err != nil {
+			switch poe.Err.(type) {
+			case *build.NoGoError:
+				noGoErrors++
+			default:
+				pkgErrors++
+			}
+		}
+	}
+	if len(m) == 0 || len(m) == noGoErrors {
+		return errors.New("all dirs lacked any go code")
+	}
+
+	if len(m) == pkgErrors {
+		return errors.New("all dirs had go code with errors")
+	}
+
+	if len(m) == pkgErrors+noGoErrors {
+		return fmt.Errorf("%d dirs had errors and %d had no go code", pkgErrors, noGoErrors)
+	}
+
+	return nil
+}

cmd/dep/testdata/harness_tests/ensure/empty/case3/final/lock.json

@@ -0,0 +1,4 @@
+{
+    "memo": "",
+    "projects": []
+}

cmd/dep/testdata/harness_tests/ensure/empty/case3/final/manifest.json

@@ -0,0 +1 @@
+{}

cmd/dep/testdata/harness_tests/ensure/empty/case3/testcase.json

@@ -0,0 +1,6 @@
+{
+  "commands": [
+    ["init"],
+    ["ensure"]
+  ]
+}