Fix the returned schema object for broken views (#12713)

The logic added in #12675 has a
small issue. When a view is found that has an error, it's not present
anymore when a subsequent `.ToSQL()` call happens, so it looks like the
view disappears.

We should never have a view disappear since that could potentially break
things and lead to unexpected results.

Signed-off-by: Dirkjan Bussink <d.bussink@gmail.com>

go/vt/schemadiff/schema.go

@@ -70,10 +70,8 @@ func NewSchemaFromEntities(entities []Entity) (*Schema, error) {
 			return nil, &UnsupportedEntityError{Entity: c.Name(), Statement: c.Create().CanonicalStatementString()}
 		}
 	}
-	if err := schema.normalize(); err != nil {
-		return schema, err
-	}
-	return schema, nil
+	err := schema.normalize()
+	return schema, err
 }
 
 // NewSchemaFromStatements creates a valid and normalized schema based on list of valid statements
@@ -309,16 +307,18 @@ func (s *Schema) normalize() error {
 		// - two or more views have a circular dependency
 		for _, t := range s.tables {
 			if _, ok := dependencyLevels[t.Name()]; !ok {
-				// We _know_ that in this iteration, at least one view is found unassigned a dependency level.
+				// We _know_ that in this iteration, at least one foreign key is not found.
 				// We return the first one.
 				return &ForeignKeyDependencyUnresolvedError{Table: t.Name()}
 			}
 		}
 		for _, v := range s.views {
 			if _, ok := dependencyLevels[v.Name()]; !ok {
 				// We _know_ that in this iteration, at least one view is found unassigned a dependency level.
-				// We return the first one.
+				// We gather all the errors.
 				errs = errors.Join(errs, &ViewDependencyUnresolvedError{View: v.ViewName.Name.String()})
+				// 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

@@ -114,9 +114,12 @@ func TestNewSchemaFromQueriesUnresolved(t *testing.T) {
 	queries := append(createQueries,
 		"create view v7 as select * from v8, t2",
 	)
-	_, err := NewSchemaFromQueries(queries)
+	schema, err := NewSchemaFromQueries(queries)
 	assert.Error(t, err)
 	assert.EqualError(t, err, (&ViewDependencyUnresolvedError{View: "v7"}).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 TestNewSchemaFromQueriesUnresolvedAlias(t *testing.T) {