schemadiff: ViewDependencyUnresolvedError lists missing referenced entities (vitessio#17711)

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>
Signed-off-by: Dirkjan Bussink <d.bussink@gmail.com>
Co-authored-by: Dirkjan Bussink <d.bussink@gmail.com>

Author: shlomi-noach

go/vt/schemadiff/errors.go

@@ -389,11 +389,20 @@ func (e *IndexNeededByForeignKeyError) Error() string {
 }
 
 type ViewDependencyUnresolvedError struct {
-	View string
+	View                      string
+	MissingReferencedEntities []string
 }
 
 func (e *ViewDependencyUnresolvedError) Error() string {
-	return fmt.Sprintf("view %s has unresolved/loop dependencies", sqlescape.EscapeID(e.View))
+	var b strings.Builder
+	fmt.Fprintf(&b, "view %s has unresolved/loop dependencies: ", sqlescape.EscapeID(e.View))
+	for i, entity := range e.MissingReferencedEntities {
+		if i > 0 {
+			b.WriteString(", ")
+		}
+		sqlescape.WriteEscapeID(&b, entity)
+	}
+	return b.String()
 }
 
 type InvalidColumnReferencedInViewError struct {

go/vt/schemadiff/schema.go

@@ -341,7 +341,14 @@ func (s *Schema) normalize(hints *DiffHints) error {
 			if _, ok := dependencyLevels[v.Name()]; !ok {
 				// We _know_ that in this iteration, at least one view is found unassigned a dependency level.
 				// We gather all the errors.
-				errs = errors.Join(errs, &ViewDependencyUnresolvedError{View: v.ViewName.Name.String()})
+				dependentNames := getViewDependentTableNames(v.CreateView)
+				missingReferencedEntities := []string{}
+				for _, name := range dependentNames {
+					if _, ok := dependencyLevels[name]; !ok {
+						missingReferencedEntities = append(missingReferencedEntities, name)
+					}
+				}
+				errs = errors.Join(errs, &ViewDependencyUnresolvedError{View: v.ViewName.Name.String(), MissingReferencedEntities: missingReferencedEntities})
 				// We still add it so it shows up in the output if that is used for anything.
 				s.sorted = append(s.sorted, v)
 			}

go/vt/schemadiff/schema_test.go

@@ -119,12 +119,26 @@ func TestNewSchemaFromQueriesUnresolved(t *testing.T) {
 	)
 	schema, err := NewSchemaFromQueries(NewTestEnv(), queries)
 	assert.Error(t, err)
-	assert.EqualError(t, err, (&ViewDependencyUnresolvedError{View: "v7"}).Error())
+	assert.EqualError(t, err, (&ViewDependencyUnresolvedError{View: "v7", MissingReferencedEntities: []string{"v8"}}).Error())
 	v := schema.sorted[len(schema.sorted)-1]
 	assert.IsType(t, &CreateViewEntity{}, v)
 	assert.Equal(t, "CREATE VIEW `v7` AS SELECT * FROM `v8`, `t2`", v.Create().CanonicalStatementString())
 }
 
+func TestNewSchemaFromQueriesUnresolvedMulti(t *testing.T) {
+	// v8 does not exist
+	queries := append(schemaTestCreateQueries,
+		"create view v7 as select * from v8, t2, t20, v21",
+	)
+	schema, err := NewSchemaFromQueries(NewTestEnv(), queries)
+	assert.Error(t, err)
+	assert.EqualError(t, err, (&ViewDependencyUnresolvedError{View: "v7", MissingReferencedEntities: []string{"v8", "t20", "v21"}}).Error())
+	assert.Equal(t, "view `v7` has unresolved/loop dependencies: `v8`, `t20`, `v21`", err.Error())
+	v := schema.sorted[len(schema.sorted)-1]
+	assert.IsType(t, &CreateViewEntity{}, v)
+	assert.Equal(t, "CREATE VIEW `v7` AS SELECT * FROM `v8`, `t2`, `t20`, `v21`", v.Create().CanonicalStatementString())
+}
+
 func TestNewSchemaFromQueriesWithSQLKeyword(t *testing.T) {
 	queries := []string{
 		"create table `order` (id int primary key, info int not null)",
@@ -141,7 +155,7 @@ func TestNewSchemaFromQueriesUnresolvedAlias(t *testing.T) {
 	)
 	_, err := NewSchemaFromQueries(NewTestEnv(), queries)
 	assert.Error(t, err)
-	assert.EqualError(t, err, (&ViewDependencyUnresolvedError{View: "v7"}).Error())
+	assert.EqualError(t, err, (&ViewDependencyUnresolvedError{View: "v7", MissingReferencedEntities: []string{"something_else"}}).Error())
 }
 
 func TestNewSchemaFromQueriesViewFromDual(t *testing.T) {
@@ -171,7 +185,7 @@ func TestNewSchemaFromQueriesLoop(t *testing.T) {
 	_, err := NewSchemaFromQueries(NewTestEnv(), queries)
 	require.Error(t, err)
 	err = vterrors.UnwrapFirst(err)
-	assert.EqualError(t, err, (&ViewDependencyUnresolvedError{View: "v7"}).Error())
+	assert.EqualError(t, err, (&ViewDependencyUnresolvedError{View: "v7", MissingReferencedEntities: []string{"v8"}}).Error())
 }
 
 func TestToSQL(t *testing.T) {
@@ -582,7 +596,7 @@ SELECT
     ) AS ranking
 FROM users AS u JOIN earnings AS e ON e.user_id = u.id;
 `,
-			expectErr: &ViewDependencyUnresolvedError{View: "user_earnings_ranking"},
+			expectErr: &ViewDependencyUnresolvedError{View: "user_earnings_ranking", MissingReferencedEntities: []string{"earnings"}},
 		},
 	}
 	for _, ts := range tt {