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// Copyright 2025 CUE Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package cueexperiment
import (
"errors"
"fmt"
"reflect"
"strings"
"cuelang.org/go/internal/mod/semver"
)
func parseExperiments(x ...string) (m map[string]bool) {
for _, a := range x {
if a == "" {
continue
}
if m == nil {
m = make(map[string]bool)
}
for _, elem := range strings.Split(a, ",") {
m[strings.TrimSpace(elem)] = true
}
}
return m
}
// parseConfig initializes the fields in flags from the attached struct field
// tags as well as the contents of the given string, which is a comma-separated
// list of experiment names.
//
// version is the language version associated with th module of a file. An empty
// version string indicates the latest language version supported by the
// compiler.
//
// experiments is a comma-separated list of experiment names.
//
// The struct field tag indicates the life cycle of the experiment, starting
// with the version from when it was introduced, the version where it became
// default, and the version where it was rejected or accepted.
//
// Experiments are all lowercase. Field names are converted to lower case.
func parseConfig[T any](flags *T, version string, experiments map[string]bool) error {
var errs []error
// Collect the field indices and set the default values.
fv := reflect.ValueOf(flags).Elem()
ft := fv.Type()
outer:
for i := range ft.NumField() {
field := ft.Field(i)
if tagStr, ok := field.Tag.Lookup("experiment"); ok {
name := strings.ToLower(field.Name)
for _, f := range strings.Split(tagStr, ",") {
key, rest, _ := strings.Cut(f, ":")
switch key {
case "since":
switch {
case !experiments[name]:
case version != "" && semver.Compare(version, rest) < 0:
const msg = "cannot set experiment %q before version %s"
errs = append(errs, fmt.Errorf(msg, name, rest))
continue outer
default:
fv.Field(i).Set(reflect.ValueOf(true))
}
case "accepted":
if version == "" || semver.Compare(version, rest) >= 0 {
fv.Field(i).Set(reflect.ValueOf(true))
}
case "rejected":
expired := (version == "" || semver.Compare(version, rest) >= 0)
if expired && experiments[name] {
const msg = "cannot set rejected experiment %q"
errs = append(errs, fmt.Errorf(msg, name))
continue outer
}
default:
panic(fmt.Errorf("unknown exp tag %q", f))
}
}
delete(experiments, name)
}
}
for name := range experiments {
errs = append(errs, fmt.Errorf("unknown experiment %q", name))
}
return errors.Join(errs...)
}
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