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// Copyright 2025 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
package aflow
import (
"bytes"
"fmt"
"io"
"reflect"
"strings"
"text/template"
"text/template/parse"
)
// formatTemplate formats template 'text' using the standard text/template logic.
// Panics on any errors, but these panics shouldn't happen if verifyTemplate
// was called for the template before.
func formatTemplate(text string, state map[string]any) string {
templ, err := parseTemplate(text)
if err != nil {
panic(err)
}
w := new(bytes.Buffer)
if err := templ.Execute(w, state); err != nil {
panic(err)
}
return w.String()
}
// verifyTemplate checks that the template 'text' can be executed with the variables 'vars'.
// Returns the set of variables that are actually used in the template.
func verifyTemplate(text string, vars map[string]reflect.Type) (map[string]bool, error) {
templ, err := parseTemplate(text)
if err != nil {
return nil, err
}
used := make(map[string]bool)
walkTemplate(templ.Root, used, &err)
if err != nil {
return nil, err
}
vals := make(map[string]any)
for name := range used {
typ, ok := vars[name]
if !ok {
return nil, fmt.Errorf("input %v is not provided", name)
}
vals[name] = reflect.Zero(typ).Interface()
}
// Execute once just to make sure.
if err := templ.Execute(io.Discard, vals); err != nil {
return nil, err
}
return used, nil
}
// walkTemplate recursively walks template nodes collecting used variables.
// It does not handle all node types, but enough to support reasonably simple templates.
func walkTemplate(n parse.Node, used map[string]bool, errp *error) {
if reflect.ValueOf(n).IsNil() {
return
}
switch n := n.(type) {
case *parse.ListNode:
for _, c := range n.Nodes {
walkTemplate(c, used, errp)
}
case *parse.IfNode:
walkTemplate(n.Pipe, used, errp)
walkTemplate(n.List, used, errp)
walkTemplate(n.ElseList, used, errp)
case *parse.RangeNode:
walkTemplate(n.Pipe, used, errp)
walkTemplate(n.List, used, errp)
walkTemplate(n.ElseList, used, errp)
case *parse.ActionNode:
walkTemplate(n.Pipe, used, errp)
case *parse.PipeNode:
for _, c := range n.Decl {
walkTemplate(c, used, errp)
}
for _, c := range n.Cmds {
walkTemplate(c, used, errp)
}
case *parse.CommandNode:
for _, c := range n.Args {
walkTemplate(c, used, errp)
}
case *parse.FieldNode:
if len(n.Ident) != 1 {
noteError(errp, "compound values are not supported: .%v", strings.Join(n.Ident, "."))
}
used[n.Ident[0]] = true
case *parse.VariableNode:
case *parse.TextNode:
default:
noteError(errp, "unhandled node type %T", n)
}
}
func parseTemplate(prompt string) (*template.Template, error) {
return template.New("").Option("missingkey=error").Parse(prompt)
}
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