vendor: update buildkit to master@31c870e82a48

Signed-off-by: Justin Chadwell <me@jedevc.com>

vendor/google.golang.org/protobuf/reflect/protopath/path.go

@@ -0,0 +1,122 @@
+// Copyright 2020 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 protopath provides functionality for
+// representing a sequence of protobuf reflection operations on a message.
+package protopath
+
+import (
+	"fmt"
+
+	"google.golang.org/protobuf/internal/msgfmt"
+	"google.golang.org/protobuf/reflect/protoreflect"
+)
+
+// NOTE: The Path and Values are separate types here since there are use cases
+// where you would like to "address" some value in a message with just the path
+// and don't have the value information available.
+//
+// This is different from how "github.com/google/go-cmp/cmp".Path operates,
+// which combines both path and value information together.
+// Since the cmp package itself is the only one ever constructing a cmp.Path,
+// it will always have the value available.
+
+// Path is a sequence of protobuf reflection steps applied to some root
+// protobuf message value to arrive at the current value.
+// The first step must be a Root step.
+type Path []Step
+
+// TODO: Provide a Parse function that parses something similar to or
+// perhaps identical to the output of Path.String.
+
+// Index returns the ith step in the path and supports negative indexing.
+// A negative index starts counting from the tail of the Path such that -1
+// refers to the last step, -2 refers to the second-to-last step, and so on.
+// It returns a zero Step value if the index is out-of-bounds.
+func (p Path) Index(i int) Step {
+	if i < 0 {
+		i = len(p) + i
+	}
+	if i < 0 || i >= len(p) {
+		return Step{}
+	}
+	return p[i]
+}
+
+// String returns a structured representation of the path
+// by concatenating the string representation of every path step.
+func (p Path) String() string {
+	var b []byte
+	for _, s := range p {
+		b = s.appendString(b)
+	}
+	return string(b)
+}
+
+// Values is a Path paired with a sequence of values at each step.
+// The lengths of Path and Values must be identical.
+// The first step must be a Root step and
+// the first value must be a concrete message value.
+type Values struct {
+	Path   Path
+	Values []protoreflect.Value
+}
+
+// Len reports the length of the path and values.
+// If the path and values have differing length, it returns the minimum length.
+func (p Values) Len() int {
+	n := len(p.Path)
+	if n > len(p.Values) {
+		n = len(p.Values)
+	}
+	return n
+}
+
+// Index returns the ith step and value and supports negative indexing.
+// A negative index starts counting from the tail of the Values such that -1
+// refers to the last pair, -2 refers to the second-to-last pair, and so on.
+func (p Values) Index(i int) (out struct {
+	Step  Step
+	Value protoreflect.Value
+}) {
+	// NOTE: This returns a single struct instead of two return values so that
+	// callers can make use of the the value in an expression:
+	//	vs.Index(i).Value.Interface()
+	n := p.Len()
+	if i < 0 {
+		i = n + i
+	}
+	if i < 0 || i >= n {
+		return out
+	}
+	out.Step = p.Path[i]
+	out.Value = p.Values[i]
+	return out
+}
+
+// String returns a humanly readable representation of the path and last value.
+// Do not depend on the output being stable.
+//
+// For example:
+//
+//	(path.to.MyMessage).list_field[5].map_field["hello"] = {hello: "world"}
+func (p Values) String() string {
+	n := p.Len()
+	if n == 0 {
+		return ""
+	}
+
+	// Determine the field descriptor associated with the last step.
+	var fd protoreflect.FieldDescriptor
+	last := p.Index(-1)
+	switch last.Step.kind {
+	case FieldAccessStep:
+		fd = last.Step.FieldDescriptor()
+	case MapIndexStep, ListIndexStep:
+		fd = p.Index(-2).Step.FieldDescriptor()
+	}
+
+	// Format the full path with the last value.
+	return fmt.Sprintf("%v = %v", p.Path[:n], msgfmt.FormatValue(last.Value, fd))
+}