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// This is a 'go generate'-oriented program for producing the "Variables"
// method on every Expression implementation found within this package.
// All expressions share the same implementation for this method, which
// just wraps the package-level function "Variables" and uses an AST walk
// to do its work.
// +build ignore
package main
import (
"fmt"
"go/ast"
"go/parser"
"go/token"
"os"
"sort"
)
func main() {
fs := token.NewFileSet()
pkgs, err := parser.ParseDir(fs, ".", nil, 0)
if err != nil {
fmt.Fprintf(os.Stderr, "error while parsing: %s\n", err)
os.Exit(1)
}
pkg := pkgs["hclsyntax"]
// Walk all the files and collect the receivers of any "Value" methods
// that look like they are trying to implement Expression.
var recvs []string
for _, f := range pkg.Files {
for _, decl := range f.Decls {
fd, ok := decl.(*ast.FuncDecl)
if !ok {
continue
}
if fd.Name.Name != "Value" {
continue
}
results := fd.Type.Results.List
if len(results) != 2 {
continue
}
valResult := fd.Type.Results.List[0].Type.(*ast.SelectorExpr).X.(*ast.Ident)
diagsResult := fd.Type.Results.List[1].Type.(*ast.SelectorExpr).X.(*ast.Ident)
if valResult.Name != "cty" && diagsResult.Name != "hcl" {
continue
}
// If we have a method called Value and it returns something in
// "cty" followed by something in "hcl" then that's specific enough
// for now, even though this is not 100% exact as a correct
// implementation of Value.
recvTy := fd.Recv.List[0].Type
switch rtt := recvTy.(type) {
case *ast.StarExpr:
name := rtt.X.(*ast.Ident).Name
recvs = append(recvs, fmt.Sprintf("*%s", name))
default:
fmt.Fprintf(os.Stderr, "don't know what to do with a %T receiver\n", recvTy)
}
}
}
sort.Strings(recvs)
of, err := os.OpenFile("expression_vars.go", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, os.ModePerm)
if err != nil {
fmt.Fprintf(os.Stderr, "failed to open output file: %s\n", err)
os.Exit(1)
}
fmt.Fprint(of, outputPreamble)
for _, recv := range recvs {
fmt.Fprintf(of, outputMethodFmt, recv)
}
fmt.Fprint(of, "\n")
}
const outputPreamble = `package hclsyntax
// Generated by expression_vars_get.go. DO NOT EDIT.
// Run 'go generate' on this package to update the set of functions here.
import (
"github.com/hashicorp/hcl2/hcl"
)`
const outputMethodFmt = `
func (e %s) Variables() []hcl.Traversal {
return Variables(e)
}`
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