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validation: add generic validation framework (#2480)
* [wip] validation framework Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * [wip] wip Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * working for shallow structs!!! Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix needle pointer deref Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * add comment Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix nested structs Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix nested struct pointers Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * add tests Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix slices / arrays Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix struct parsing Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * extend tests Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * expose API Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * extend in-package documentation Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * linter fixes Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * fix naming Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * add missing license headers Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> * Apply suggestions from code review Co-authored-by: Daniel Weiße <66256922+daniel-weisse@users.noreply.github.com> * align with review Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> --------- Signed-off-by: Moritz Sanft <58110325+msanft@users.noreply.github.com> Co-authored-by: Daniel Weiße <66256922+daniel-weisse@users.noreply.github.com>
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Moritz Sanft
GitHub
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269
internal/validation/errors.go
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269
internal/validation/errors.go
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@ -0,0 +1,269 @@
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/*
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Copyright (c) Edgeless Systems GmbH
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SPDX-License-Identifier: AGPL-3.0-only
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*/
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package validation
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import (
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"errors"
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"fmt"
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"reflect"
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"strings"
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)
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// Error is returned when a document is not valid.
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type Error struct {
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Path string
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Err error
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}
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/*
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newError creates a new validation Error.
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To find the path to the exported field that failed validation, it traverses "doc"
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recursively until it finds a field in "doc" that matches the reference to "field".
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*/
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func newError(doc, field referenceableValue, errMsg error) *Error {
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// traverse the top level struct (i.e. the "haystack") until addr (i.e. the "needle") is found
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path, err := traverse(doc, field, newPathBuilder(doc._type.Name()))
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if err != nil {
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return &Error{
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Path: "unknown",
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Err: fmt.Errorf("cannot find path to field: %w. original error: %w", err, errMsg),
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}
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}
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return &Error{
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Path: path,
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Err: errMsg,
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}
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}
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// Error implements the error interface.
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func (e *Error) Error() string {
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return fmt.Sprintf("validating %s: %s", e.Path, e.Err)
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}
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// Unwrap implements the error interface.
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func (e *Error) Unwrap() error {
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return e.Err
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}
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/*
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traverse "haystack" recursively until it finds a field that matches
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the reference saved in "needle", while building a pseudo-JSONPath to the field.
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If it traverses a level down, it appends the name of the struct tag
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or another entity like array index or map field to path.
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When a field matches the reference to the given field, it returns the
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path to the field.
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*/
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func traverse(haystack referenceableValue, needle referenceableValue, path pathBuilder) (string, error) {
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// recursion anchor: doc is the field we are looking for.
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// Join the path and return.
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if foundNeedle(haystack, needle) {
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return path.string(), nil
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}
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kind := haystack._type.Kind()
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switch kind {
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case reflect.Struct:
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// Traverse all visible struct fields.
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for _, field := range reflect.VisibleFields(haystack._type) {
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// skip unexported fields
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if !field.IsExported() {
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continue
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}
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fieldVal := recPointerDeref(haystack.value.FieldByName(field.Name))
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if isNilPtrOrInvalid(fieldVal) {
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continue
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}
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fieldAddr := haystack.addr + field.Offset
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newHaystack := referenceableValue{
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value: fieldVal,
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addr: fieldVal.UnsafeAddr(),
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_type: fieldVal.Type(),
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}
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if canTraverse(fieldVal) {
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// When a field is not the needle and cannot be traversed further,
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// a errCannotTraverse is returned. Therefore, we only want to handle
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// the case where the field is the needle.
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if path, err := traverse(newHaystack, needle, path.appendStructField(field)); err == nil {
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return path, nil
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}
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}
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if foundNeedle(referenceableValue{addr: fieldAddr, _type: field.Type}, needle) {
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return path.appendStructField(field).string(), nil
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}
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}
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case reflect.Slice, reflect.Array:
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// Traverse slice / Array elements
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for i := 0; i < haystack.value.Len(); i++ {
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// see struct case
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itemVal := recPointerDeref(haystack.value.Index(i))
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if isNilPtrOrInvalid(itemVal) {
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continue
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}
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newHaystack := referenceableValue{
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value: itemVal,
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addr: itemVal.UnsafeAddr(),
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_type: itemVal.Type(),
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}
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if canTraverse(itemVal) {
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if path, err := traverse(newHaystack, needle, path.appendArrayIndex(i)); err == nil {
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return path, nil
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}
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}
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if foundNeedle(newHaystack, needle) {
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return path.appendArrayIndex(i).string(), nil
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}
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}
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case reflect.Map:
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// Traverse map elements
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iter := haystack.value.MapRange()
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for iter.Next() {
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// see struct case
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mapKey := iter.Key().String()
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mapVal := recPointerDeref(iter.Value())
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if isNilPtrOrInvalid(mapVal) {
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continue
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}
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if canTraverse(mapVal) {
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newHaystack := referenceableValue{
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value: mapVal,
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addr: mapVal.UnsafeAddr(),
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_type: mapVal.Type(),
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mapKey: mapKey,
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}
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if path, err := traverse(newHaystack, needle, path.appendMapKey(mapKey)); err == nil {
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return path, nil
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}
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}
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// check if reference to map is the needle and the map key matches
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if foundNeedle(referenceableValue{addr: haystack.addr, _type: haystack._type, mapKey: mapKey}, needle) {
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return path.appendMapKey(mapKey).string(), nil
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}
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}
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}
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// Primitive type, but not the value we are looking for.
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return "", errCannotTraverse
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}
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// referenceableValue is a type that can be passed as any (thus being copied) without losing the reference to the actual value.
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type referenceableValue struct {
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value reflect.Value
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_type reflect.Type
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mapKey string // special case for map values, which are not addressable
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addr uintptr
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}
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// errCannotTraverse is returned when a field cannot be traversed further.
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var errCannotTraverse = errors.New("cannot traverse anymore")
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// recPointerDeref recursively dereferences pointers and unpacks interfaces until a non-pointer value is found.
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func recPointerDeref(val reflect.Value) reflect.Value {
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switch val.Kind() {
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case reflect.Ptr, reflect.UnsafePointer, reflect.Interface:
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return recPointerDeref(val.Elem())
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}
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return val
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}
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// pointerDeref dereferences pointers and unpacks interfaces.
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// If the value is not a pointer, it is returned unchanged.
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func pointerDeref(val reflect.Value) reflect.Value {
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switch val.Kind() {
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case reflect.Ptr, reflect.UnsafePointer, reflect.Interface:
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return val.Elem()
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}
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return val
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}
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/*
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canTraverse whether a value can be further traversed.
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For pointer types, false is returned.
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*/
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func canTraverse(v reflect.Value) bool {
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switch v.Kind() {
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case reflect.Struct, reflect.Slice, reflect.Array, reflect.Map:
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return true
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}
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return false
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}
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// isNilPtrOrInvalid returns true if a value is a nil pointer or if the value is of an invalid kind.
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func isNilPtrOrInvalid(v reflect.Value) bool {
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switch v.Kind() {
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case reflect.Ptr, reflect.UnsafePointer, reflect.Interface, reflect.Slice, reflect.Map:
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return v.IsNil()
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case reflect.Invalid:
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return true
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}
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return false
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}
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/*
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foundNeedle returns whether the given value is the needle.
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It does so by comparing the address and type of the value to the address and type of the needle.
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The comparison of types is necessary because the first value of a struct has the same address as the struct itself.
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*/
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func foundNeedle(haystack, needle referenceableValue) bool {
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return haystack.addr == needle.addr &&
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haystack._type == needle._type &&
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haystack.mapKey == needle.mapKey
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}
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// pathBuilder is a helper to build a field path.
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type pathBuilder struct {
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buf []string // slice can be copied by value when its non-zero, contrary to a strings.Builder
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}
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// newPathBuilder creates a new pathBuilder from the identifier of a top level document.
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func newPathBuilder(topLevelDoc string) pathBuilder {
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return pathBuilder{
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buf: []string{topLevelDoc},
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}
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}
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// appendStructField appends the JSON / YAML struct tag of a field to the path.
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// If no struct tag is present, the field name is used.
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func (p pathBuilder) appendStructField(field reflect.StructField) pathBuilder {
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switch {
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case field.Tag.Get("json") != "":
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p.buf = append(p.buf, fmt.Sprintf(".%s", field.Tag.Get("json")))
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case field.Tag.Get("yaml") != "":
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p.buf = append(p.buf, fmt.Sprintf(".%s", field.Tag.Get("yaml")))
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default:
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p.buf = append(p.buf, fmt.Sprintf(".%s", field.Name))
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}
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return p
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}
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// appendArrayIndex appends the index of an array to the path.
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func (p pathBuilder) appendArrayIndex(i int) pathBuilder {
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p.buf = append(p.buf, fmt.Sprintf("[%d]", i))
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return p
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}
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// appendMapKey appends the key of a map to the path.
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func (p pathBuilder) appendMapKey(k string) pathBuilder {
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p.buf = append(p.buf, fmt.Sprintf("[\"%s\"]", k))
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return p
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}
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// string returns the path.
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func (p pathBuilder) string() string {
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// Remove struct tag prefix
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return strings.TrimPrefix(
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strings.Join(p.buf, ""),
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".",
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)
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}
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