better wording of errors

fix nil being passed to errors.Wrap()

Signed-off-by: Jess Frazelle <acidburn@google.com>

ensure.go

@@ -111,6 +111,7 @@ func (cmd *ensureCommand) Run(args []string) error {
 		pc, err := getProjectConstraint(arg, sm)
 		if err != nil {
 			errs = append(errs, err)
+			continue
 		}
 
 		if gps.IsAny(pc.Constraint) && pc.Ident.Source == "" {
@@ -145,6 +146,7 @@ func (cmd *ensureCommand) Run(args []string) error {
 		pc, err := getProjectConstraint(ovr, sm)
 		if err != nil {
 			errs = append(errs, err)
+			continue
 		}
 
 		// Empty overrides are fine (in contrast to deps), because they actually
@@ -166,7 +168,7 @@ func (cmd *ensureCommand) Run(args []string) error {
 
 	if len(errs) > 0 {
 		var buf bytes.Buffer
-		for err := range errs {
+		for _, err := range errs {
 			fmt.Fprintln(&buf, err)
 		}
 
@@ -293,7 +295,7 @@ func getProjectConstraint(arg string, sm *gps.SourceMgr) (gps.ProjectConstraint,
 	}
 
 	if string(pr) != arg {
-		return constraint, errors.Wrapf(err, "dependency path %s is not a project root", arg)
+		return constraint, fmt.Errorf("dependency path %s is not a project root, try %s instead", arg, pr)
 	}
 	constraint.Ident.ProjectRoot = gps.ProjectRoot(arg)
 

main.go

@@ -138,7 +138,7 @@ func resetUsage(fs *flag.FlagSet, name, args, longHelp string) {
 }
 
 var (
-	errProjectNotFound = errors.New("no project could be found")
+	errProjectNotFound = errors.New("could not find project manifest.json")
 )
 
 func findProjectRootFromWD() (string, error) {

manifest.go

@@ -150,7 +150,7 @@ func toPossible(pp gps.ProjectProperties) (p possibleProps) {
 		// the 'any' case, because that's the other possibility, and it's what
 		// we interpret not having any constraint expressions at all to mean.
 		//if !gps.IsAny(pp.Constraint) && !gps.IsNone(pp.Constraint) {
-		if !gps.IsAny(pp.Constraint) {
+		if !gps.IsAny(pp.Constraint) && pp.Constraint != nil {
 			// Has to be a semver range.
 			p.Version = pp.Constraint.String()
 		}