internal/gps: add solver.validateParams() method

Signed-off-by: Ibrahim AshShohail <ibra.sho@gmail.com>

cmd/dep/ensure.go

@@ -144,21 +144,19 @@ func (cmd *ensureCommand) Run(ctx *dep.Ctx, args []string) error {
 
 	solver, err := gps.Prepare(params, sm)
 	if err != nil {
-		if deduceErrs, ok := err.(gps.DeductionFailureErrs); ok {
-			ctx.Loggers.Err.Println("The following errors occurred while deducing packages:")
-			for ip, error := range deduceErrs {
-				ctx.Loggers.Err.Printf("  * \"%s\": %s", ip, error)
-			}
-			ctx.Loggers.Err.Println()
-
-			return errors.New("could not deduce packages to ensure constraints")
-		}
 		return errors.Wrap(err, "ensure Prepare")
 	}
 
 	solution, err := solver.Solve()
 	if err != nil {
 		handleAllTheFailuresOfTheWorld(err)
+		if deduceErrs, ok := err.(gps.DeductionFailureErrs); ok {
+			ctx.Loggers.Err.Println("The following errors occurred while deducing packages:")
+			for ip, dErr := range deduceErrs {
+				ctx.Loggers.Err.Printf("  * \"%s\": %s", ip, dErr)
+			}
+			ctx.Loggers.Err.Println()
+		}
 		return errors.Wrap(err, "ensure Solve()")
 	}
 

internal/gps/solve_failures.go

@@ -243,7 +243,7 @@ func (e badOptsFailure) Error() string {
 type DeductionFailureErrs map[string]error
 
 func (e DeductionFailureErrs) Error() string {
-	return fmt.Sprintf("%v", e)
+	return "could not deduce packages to ensure constraints are solvable"
 }
 
 type sourceMismatchFailure struct {

internal/gps/solver.go

@@ -290,28 +290,6 @@ func Prepare(params SolveParameters, sm SourceManager) (Solver, error) {
 		rd:       rd,
 	}
 
-	var deducePkgsGroup sync.WaitGroup
-	deductionErrs := make(DeductionFailureErrs)
-
-	checkPkg := func(ip string, sm SourceManager) {
-		_, err := sm.DeduceProjectRoot(ip)
-		if err != nil {
-			deductionErrs[ip] = err
-		}
-		deducePkgsGroup.Done()
-	}
-
-	for _, ip := range rd.externalImportList(params.stdLibFn) {
-		deducePkgsGroup.Add(1)
-		go checkPkg(ip, sm)
-	}
-
-	deducePkgsGroup.Wait()
-
-	if len(deductionErrs) > 0 {
-		return nil, deductionErrs
-	}
-
 	// Set up the bridge and ensure the root dir is in good, working order
 	// before doing anything else.
 	if params.mkBridgeFn == nil {
@@ -413,9 +391,13 @@ func (s *solver) Solve() (Solution, error) {
 	s.mtr = newMetrics()
 	s.vUnify.mtr = s.mtr
 
+	// Validate the solver parameters
+	if err := s.validateParams(); err != nil {
+		return nil, err
+	}
+
 	// Prime the queues with the root project
-	err := s.selectRoot()
-	if err != nil {
+	if err := s.selectRoot(); err != nil {
 		return nil, err
 	}
 
@@ -556,6 +538,37 @@ func (s *solver) solve() (map[atom]map[string]struct{}, error) {
 	return projs, nil
 }
 
+// validateParams validates the solver parameters to ensure solving can be completed.
+func (s *solver) validateParams() error {
+	// Ensure that all packages are deducible without issues.
+	var deducePkgsGroup sync.WaitGroup
+	deductionErrs := make(DeductionFailureErrs)
+	var errsMut sync.Mutex
+
+	deducePkg := func(ip string, s *solver) {
+		_, err := s.b.DeduceProjectRoot(ip)
+		if err != nil {
+			errsMut.Lock()
+			deductionErrs[ip] = err
+			errsMut.Unlock()
+		}
+		deducePkgsGroup.Done()
+	}
+
+	for _, ip := range s.rd.externalImportList(s.stdLibFn) {
+		deducePkgsGroup.Add(1)
+		go deducePkg(ip, s)
+	}
+
+	deducePkgsGroup.Wait()
+
+	if len(deductionErrs) > 0 {
+		return deductionErrs
+	}
+
+	return nil
+}
+
 // selectRoot is a specialized selectAtom, used solely to initially
 // populate the queues at the beginning of a solve run.
 func (s *solver) selectRoot() error {