Add check that dep pkgs exist on selected project

errors.go

@@ -307,3 +307,76 @@ func (e *checkeeHasProblemPackagesFailure) traceString() string {
 
 	return buf.String()
 }
+
+type depHasProblemPackagesFailure struct {
+	goal Dependency
+	v    Version
+	pl   []string
+	prob map[string]error
+}
+
+func (e *depHasProblemPackagesFailure) Error() string {
+	fcause := func(pkg string) string {
+		var cause string
+		if err, has := e.prob[pkg]; has {
+			cause = fmt.Sprintf("does not contain usable Go code (%T).", err)
+		} else {
+			cause = "is missing."
+		}
+		return cause
+	}
+
+	if len(e.pl) == 1 {
+		return fmt.Sprintf(
+			"Could not introduce %s at %s, as it requires package %s from %s, but in version %s that package %s",
+			e.goal.Depender.Ident.errString(),
+			e.goal.Depender.Version,
+			e.pl[0],
+			e.goal.Dep.Ident.errString(),
+			e.v,
+			fcause(e.pl[0]),
+		)
+	}
+
+	var buf bytes.Buffer
+	fmt.Fprintf(
+		&buf, "Could not introduce %s at %s, as it requires problematic packages from %s (current version %s):",
+		e.goal.Depender.Ident.errString(),
+		e.goal.Depender.Version,
+		e.goal.Dep.Ident.errString(),
+		e.v,
+	)
+
+	for _, pkg := range e.pl {
+		fmt.Fprintf(&buf, "\t%s %s", pkg, fcause(pkg))
+	}
+
+	return buf.String()
+}
+
+func (e *depHasProblemPackagesFailure) traceString() string {
+	var buf bytes.Buffer
+	fcause := func(pkg string) string {
+		var cause string
+		if err, has := e.prob[pkg]; has {
+			cause = fmt.Sprintf("has parsing err (%T).", err)
+		} else {
+			cause = "is missing"
+		}
+		return cause
+	}
+
+	fmt.Fprintf(
+		&buf, "%s at %s depping on %s at %s has problem subpkg(s):",
+		e.goal.Depender.Ident.errString(),
+		e.goal.Depender.Version,
+		e.goal.Dep.Ident.errString(),
+		e.v,
+	)
+
+	for _, pkg := range e.pl {
+		fmt.Fprintf(&buf, "\t%s %s", pkg, fcause(pkg))
+	}
+
+	return buf.String()
+}

satisfy.go

@@ -35,6 +35,9 @@ func (s *solver) checkProject(a atomWithPackages) error {
 		if err := s.checkDepsDisallowsSelected(a, dep); err != nil {
 			return err
 		}
+		if err := s.checkPackageImportsFromDepExist(a, dep); err != nil {
+			return err
+		}
 
 		// TODO add check that fails if adding this atom would create a loop
 	}
@@ -70,6 +73,9 @@ func (s *solver) checkPackage(a atomWithPackages) error {
 		if err := s.checkDepsDisallowsSelected(a, dep); err != nil {
 			return err
 		}
+		if err := s.checkPackageImportsFromDepExist(a, dep); err != nil {
+			return err
+		}
 	}
 
 	return nil
@@ -135,10 +141,12 @@ func (s *solver) checkRequiredPackagesExist(a atomWithPackages) error {
 	}
 
 	if len(fp) > 0 {
-		return &checkeeHasProblemPackagesFailure{
+		e := &checkeeHasProblemPackagesFailure{
 			goal:    a.atom,
 			failpkg: fp,
 		}
+		s.logSolve(e)
+		return e
 	}
 	return nil
 }
@@ -228,3 +236,44 @@ func (s *solver) checkIdentMatches(a atomWithPackages, cdep completeDep) error {
 
 	return nil
 }
+
+// checkPackageImportsFromDepExist ensures that, if the dep is already selected,
+// the newly-required set of packages being placed on it exist and are valid.
+func (s *solver) checkPackageImportsFromDepExist(a atomWithPackages, cdep completeDep) error {
+	sel, is := s.sel.selected(cdep.ProjectDep.Ident)
+	if !is {
+		// dep is not already selected; nothing to do
+		return nil
+	}
+
+	ptree, err := s.b.listPackages(sel.atom.Ident, sel.atom.Version)
+	if err != nil {
+		// TODO handle this more gracefully
+		return err
+	}
+
+	e := &depHasProblemPackagesFailure{
+		goal: Dependency{
+			Depender: a.atom,
+			Dep:      cdep,
+		},
+		v:    sel.atom.Version,
+		prob: make(map[string]error),
+	}
+
+	for _, pkg := range cdep.pl {
+		perr, has := ptree.Packages[pkg]
+		if !has || perr.Err != nil {
+			e.pl = append(e.pl, pkg)
+			if has {
+				e.prob[pkg] = perr.Err
+			}
+		}
+	}
+
+	if len(e.pl) > 0 {
+		s.logSolve(e)
+		return e
+	}
+	return nil
+}

solve_bimodal_test.go

@@ -345,7 +345,7 @@ var bimodalFixtures = map[string]bimodalFixture{
 				pkg("d", "a/nonexistent"),
 			),
 		},
-		errp: []string{"d", "a"},
+		errp: []string{"d", "a", "d"},
 	},
 }
 

solve_test.go

@@ -303,6 +303,8 @@ func getFailureCausingProjects(err error) (projs []string) {
 				projs = append(projs, string(atom.Ident.LocalName))
 			}
 		}
+	case *depHasProblemPackagesFailure:
+		projs = append(projs, string(e.goal.Depender.Ident.LocalName), string(e.goal.Dep.Ident.LocalName))
 	default:
 		panic("unknown failtype")
 	}