internal/gps: ensure packages are deducible before attempting to solve

Add gps.ValidateParams to ensure all packages in SolverParams are
deducible.

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

cmd/dep/ensure.go

@@ -142,6 +142,18 @@ func (cmd *ensureCommand) Run(ctx *dep.Ctx, args []string) error {
 		}
 	}
 
+	err = gps.ValidateParams(params, sm)
+	if err != nil {
+		if deduceErrs, ok := err.(gps.DeductionErrs); ok {
+			ctx.Err.Println("The following errors occurred while deducing packages:")
+			for ip, dErr := range deduceErrs {
+				ctx.Err.Printf("  * \"%s\": %s", ip, dErr)
+			}
+			ctx.Err.Println()
+		}
+		return errors.Wrap(err, "validateParams")
+	}
+
 	solver, err := gps.Prepare(params, sm)
 	if err != nil {
 		return errors.Wrap(err, "ensure Prepare")

internal/gps/hash_test.go

@@ -528,7 +528,8 @@ func TestHashInputsOverrides(t *testing.T) {
 
 		s, err := Prepare(params, newdepspecSM(basefix.ds, nil))
 		if err != nil {
-			t.Fatalf("(fix: %q) Unexpected error while prepping solver: %s", fix.name, err)
+			t.Errorf("(fix: %q) Unexpected error while prepping solver: %s", fix.name, err)
+			continue
 		}
 
 		h := sha256.New()

internal/gps/solver.go

@@ -10,6 +10,7 @@ import (
 	"log"
 	"sort"
 	"strings"
+	"sync"
 
 	"github.com/armon/go-radix"
 	"github.com/golang/dep/internal/gps/paths"
@@ -381,6 +382,50 @@ func (s *solver) Version() int {
 	return 1
 }
 
+// DeductionErrs maps package import path to errors occurring during deduction.
+type DeductionErrs map[string]error
+
+func (e DeductionErrs) Error() string {
+	return "could not deduce external imports' project roots"
+}
+
+// ValidateParams validates the solver parameters to ensure solving can be completed.
+func ValidateParams(params SolveParameters, sm SourceManager) error {
+	// Ensure that all packages are deducible without issues.
+	var deducePkgsGroup sync.WaitGroup
+	deductionErrs := make(DeductionErrs)
+	var errsMut sync.Mutex
+
+	rd, err := params.toRootdata()
+	if err != nil {
+		return err
+	}
+
+	deducePkg := func(ip string, sm SourceManager) {
+		fmt.Println(ip)
+		_, err := sm.DeduceProjectRoot(ip)
+		if err != nil {
+			errsMut.Lock()
+			deductionErrs[ip] = err
+			errsMut.Unlock()
+		}
+		deducePkgsGroup.Done()
+	}
+
+	for _, ip := range rd.externalImportList(paths.IsStandardImportPath) {
+		deducePkgsGroup.Add(1)
+		go deducePkg(ip, sm)
+	}
+
+	deducePkgsGroup.Wait()
+
+	if len(deductionErrs) > 0 {
+		return deductionErrs
+	}
+
+	return nil
+}
+
 // Solve attempts to find a dependency solution for the given project, as
 // represented by the SolveParameters with which this Solver was created.
 //
@@ -391,8 +436,7 @@ func (s *solver) Solve() (Solution, error) {
 	s.vUnify.mtr = s.mtr
 
 	// Prime the queues with the root project
-	err := s.selectRoot()
-	if err != nil {
+	if err := s.selectRoot(); err != nil {
 		return nil, err
 	}
 

internal/gps/solver_test.go

@@ -0,0 +1,62 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gps
+
+import (
+	"testing"
+
+	"github.com/golang/dep/internal/gps/pkgtree"
+	"github.com/golang/dep/internal/test"
+)
+
+func TestValidateParams(t *testing.T) {
+	h := test.NewHelper(t)
+	defer h.Cleanup()
+
+	cacheDir := "gps-cache"
+	h.TempDir(cacheDir)
+	sm, err := NewSourceManager(h.Path(cacheDir))
+	h.Must(err)
+	defer sm.Release()
+
+	h.TempDir("src")
+
+	testcases := []struct {
+		imports []string
+		err     bool
+	}{
+		{[]string{"google.com/non-existing/package"}, true},
+		{[]string{"google.com/non-existing/package/subpkg"}, true},
+		{[]string{"github.com/sdboyer/testrepo"}, false},
+		{[]string{"github.com/sdboyer/testrepo/subpkg"}, false},
+	}
+
+	params := SolveParameters{
+		ProjectAnalyzer: naiveAnalyzer{},
+		RootDir:         h.Path("src"),
+		RootPackageTree: pkgtree.PackageTree{
+			ImportRoot: "github.com/sdboyer/dep",
+		},
+	}
+
+	for _, tc := range testcases {
+		params.RootPackageTree.Packages = map[string]pkgtree.PackageOrErr{
+			"github.com/sdboyer/dep": {
+				P: pkgtree.Package{
+					Name:       "github.com/sdboyer/dep",
+					ImportPath: "github.com/sdboyer/dep",
+					Imports:    tc.imports,
+				},
+			},
+		}
+
+		err = ValidateParams(params, sm)
+		if tc.err && err == nil {
+			t.Fatalf("expected an error when deducing package fails, got none")
+		} else if !tc.err && err != nil {
+			t.Fatalf("deducing packges should have succeeded, got err: %#v", err)
+		}
+	}
+}