tools/template-check/gotemplate/gotemplate.go

package gotemplate

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"regexp"
	"strings"
)

// Note: this is allowlisted to combat other issues like `=` instead of `==`, but it is possible we
// need to add more options to this list in the future, like `private`. The main thing we want to
// prevent is targeting `beta` in version guards, because it mishandles either `ga` or `private`.

// TODO: refactor to be a regex as the permitted formats are more varied under go templates
var allowedGuards = []string{
	`{{- if ne $.TargetVersionName "ga" }}`,
	`{{ if ne $.TargetVersionName "ga" -}}`,
	`{{- if ne $.TargetVersionName "ga" -}}`,
	`{{ if ne $.TargetVersionName "ga" }}`,
	`{{- if eq $.TargetVersionName "ga" }}`,
	`{{ if eq $.TargetVersionName "ga" -}}`,
	`{{- if eq $.TargetVersionName "ga" -}}`,
	`{{ if eq $.TargetVersionName "ga" }}`,
	"{{- if ne $.TargetVersionName `ga` }}",
	"{{ if ne $.TargetVersionName `ga` -}}",
	"{{- if ne $.TargetVersionName `ga` -}}",
	"{{ if ne $.TargetVersionName `ga` }}",
	"{{- if eq $.TargetVersionName `ga` }}",
	"{{ if eq $.TargetVersionName `ga` -}}",
	"{{- if eq $.TargetVersionName `ga` -}}",
	"{{ if eq $.TargetVersionName `ga` }}",
}

// Note: this does not account for _every_ possible use of a version guard (for example, those
// starting with `version.nil?`), because the logic would start to get more complicated. Instead,
// the goal is to capture (and validate) all "standard" version guards that would be added for new
// resources/fields.
func isVersionGuard(line string) bool {
	re := regexp.MustCompile(`{{-? if (eq|ne) \$\.TargetVersionName`)
	return re.MatchString(line)
}

func isValidVersionGuard(line string) bool {
	for _, g := range allowedGuards {
		if strings.Contains(line, g) {
			return true
		}
	}
	return false
}

// CheckVersionGuards scans the input for version guards, and checks that those version guards are
// valid. Invalid version guards are returned along with the line number in which they occurred.
func CheckVersionGuards(r io.Reader) []string {
	scanner := bufio.NewScanner(r)
	lineNum := 1
	var invalidGuards []string
	for scanner.Scan() {
		if isVersionGuard(scanner.Text()) && !isValidVersionGuard(scanner.Text()) {
			invalidGuards = append(invalidGuards, fmt.Sprintf("%d: %s", lineNum, scanner.Text()))
		}
		lineNum++
	}
	return invalidGuards
}

// CheckVersionGuardsForFile scans the file for version guards, and checks that those version
// guards are valid. Invalid version guards are returned along with the line number in which they
// occurred.
func CheckVersionGuardsForFile(filename string) ([]string, error) {
	file, err := os.Open(filename)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	return CheckVersionGuards(file), nil
}