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|
package main
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"maps"
"slices"
"strings"
"cuelang.org/go/cue"
)
// kind is the base type of a scalar
type kind int
const (
kindBool kind = iota
kindInt
kindFloat
kindNumber
kindString
)
func (k kind) String() string {
return []string{"bool", "int", "float", "number", "string"}[k]
}
// scalar is a single bool, number, or string value, along with its constraints
type scalar struct {
kind kind
// Constraints from the schema
enum []any
min *bound
max *bound
regexes []scalarRegex
notEmpty bool
// @go(type, parse, import)
goType string
goParse string
goImports []string
// @nix(type, apply, import)
nixType string
nixApply string
nixImports []string
}
// scalarRegex is a regex constraint on a scalar
type scalarRegex struct {
pattern string
// goName is the Go name of the definition the regex is written in, e.g. URL for #URL, or empty if there isn't one
goName string
}
// customGo reports whether the scalar uses a custom Go type with its own parse function
func (s scalar) customGo() bool {
return s.goParse != ""
}
// field is a single field of a struct.
// It is either a nested struct, a list of scalars, or a scalar.
type field struct {
label string
path []string
goName string
doc string
optional bool
// nested is set if the field is a struct.
// Otherwise scalar describes the field, or each element if isList is set.
nested *structType
isList bool
scalar scalar
defaultValue any
hasDefault bool
nixSkip bool
nixDefault any
hasNixDefault bool
nixImports []string
// On a list field, @nix(type) and @nix(apply) are for the whole list rather than each element
nixListType string
nixListApply string
}
// flagName returns the dotted path of the field, e.g. ssh.clone-url
func (f *field) flagName() string {
return strings.Join(f.path, ".")
}
// errorf returns an error prefixed with the field's flag name
func (f *field) errorf(format string, args ...any) error {
return fmt.Errorf("%s: %w", f.flagName(), fmt.Errorf(format, args...))
}
// structType is a CUE struct, generated as a Go struct type
type structType struct {
goName string
fields []*field
}
// builder builds the model from a CUE value, making sure generated Go names don't collide
type builder struct {
names namer
typeSuffix string
// typeOwners maps each Go struct type name to the flag name of the field that uses it
typeOwners map[string]string
}
// buildModel validates v and builds the model for it, with the root struct named rootType
func buildModel(v cue.Value, rootType, typeSuffix string, names namer) (*structType, error) {
if err := v.Validate(); err != nil {
return nil, err
}
b := &builder{
names: names,
typeSuffix: typeSuffix,
typeOwners: map[string]string{
rootType: "(root)",
},
}
return b.buildStruct(v, nil, rootType)
}
// buildStruct builds the struct at path, including all of its fields
func (b *builder) buildStruct(v cue.Value, path []string, goName string) (*structType, error) {
if v.LookupPath(cue.MakePath(cue.AnyString)).Exists() {
return nil, fmt.Errorf("%s: structs with pattern constraints ([string]: T) are not supported", pathString(path))
}
iter, err := v.Fields(cue.Optional(true))
if err != nil {
return nil, fmt.Errorf("%s: %w", pathString(path), err)
}
st := &structType{goName: goName}
// fieldOwners maps each Go field name to the flag name that uses it
fieldOwners := make(map[string]string)
for iter.Next() {
fieldPath := append(slices.Clone(path), iter.Selector().Unquoted())
f, err := b.buildField(iter.Value(), fieldPath, iter.IsOptional())
if err != nil {
return nil, err
}
if owner, ok := fieldOwners[f.goName]; ok {
return nil, fmt.Errorf("%s: Go field name %s is also used by %s; set @go(name=...)", f.flagName(), f.goName, owner)
}
fieldOwners[f.goName] = f.flagName()
st.fields = append(st.fields, f)
}
return st, nil
}
// buildField builds the field at path
func (b *builder) buildField(v cue.Value, path []string, optional bool) (*field, error) {
f := &field{
label: path[len(path)-1],
path: path,
doc: docText(v),
optional: optional,
}
goAttrs, err := readAttrs(v, "go", "name", "type", "parse", "import")
if err != nil {
return nil, f.errorf("%w", err)
}
nixAttrs, err := readAttrs(v, "nix", "type", "apply", "import", "default", "skip")
if err != nil {
return nil, f.errorf("%w", err)
}
f.goName = goAttrs["name"]
if f.goName == "" {
f.goName, err = b.names.fieldName(f.label)
if err != nil {
return nil, f.errorf("%w", err)
}
}
_, f.nixSkip = nixAttrs["skip"]
switch v.IncompleteKind() {
case cue.StructKind:
if err := b.buildStructField(v, f, goAttrs, nixAttrs); err != nil {
return nil, err
}
return f, nil
case cue.ListKind:
err = b.buildListField(v, f, goAttrs, nixAttrs)
default:
err = b.buildScalarField(v, f, goAttrs, nixAttrs)
}
if err != nil {
return nil, err
}
if err := setNixImports(f, nixAttrs); err != nil {
return nil, err
}
if err := setDefaults(v, f, nixAttrs); err != nil {
return nil, err
}
return f, nil
}
// buildStructField fills in f as a nested struct
func (b *builder) buildStructField(v cue.Value, f *field, goAttrs, nixAttrs map[string]string) error {
if goAttrs["parse"] != "" || goAttrs["import"] != "" {
return f.errorf("@go(parse) and @go(import) are not allowed on structs")
}
for _, key := range []string{"default", "apply", "import"} {
if _, ok := nixAttrs[key]; ok {
return f.errorf("@nix(%s) is not allowed on structs; set it on the fields", key)
}
}
typeName := goAttrs["type"]
if typeName == "" {
var err error
typeName, err = b.names.typeName(f.label, b.typeSuffix)
if err != nil {
return f.errorf("%w", err)
}
}
if owner, ok := b.typeOwners[typeName]; ok {
return f.errorf("Go type %s is also used by %s; set @go(type=...)", typeName, owner)
}
b.typeOwners[typeName] = f.flagName()
nested, err := b.buildStruct(v, f.path, typeName)
if err != nil {
return err
}
f.nested = nested
return nil
}
// buildListField fills in f as a list of scalars
func (b *builder) buildListField(v cue.Value, f *field, goAttrs, nixAttrs map[string]string) error {
f.isList = true
elem := listElem(v)
if !elem.Exists() {
return f.errorf("only open lists ([...T]) are supported")
}
if elemKind := elem.IncompleteKind(); elemKind == cue.ListKind || elemKind == cue.StructKind {
return f.errorf("lists of %v are not supported", elemKind)
}
s, err := b.buildScalar(elem, goAttrs)
if err != nil {
return f.errorf("%w", err)
}
f.scalar = s
f.nixListType = nixAttrs["type"]
f.nixListApply = nixAttrs["apply"]
return nil
}
// buildScalarField fills in f as a scalar
func (b *builder) buildScalarField(v cue.Value, f *field, goAttrs, nixAttrs map[string]string) error {
s, err := b.buildScalar(v, goAttrs)
if err != nil {
return f.errorf("%w", err)
}
// The field's own @nix attributes win over any from a definition
if nixType := nixAttrs["type"]; nixType != "" {
s.nixType = nixType
}
if nixApply := nixAttrs["apply"]; nixApply != "" {
s.nixApply = nixApply
}
f.scalar = s
return nil
}
// setNixImports collects the names f's Nix type and apply use, and makes sure each can be a Nix function argument
func setNixImports(f *field, nixAttrs map[string]string) error {
f.nixImports = f.scalar.nixImports
if imports := nixAttrs["import"]; imports != "" {
f.nixImports = append(strings.Fields(imports), f.nixImports...)
}
for _, name := range f.nixImports {
if !nixIdent.MatchString(name) || nixKeywords[name] || nixReserved[name] {
return f.errorf("@nix(import): %q can't be a Nix function argument", name)
}
}
return nil
}
// setDefaults sets f's schema default, and its Nix default if @nix(default) is set
func setDefaults(v cue.Value, f *field, nixAttrs map[string]string) error {
if def, ok := concreteDefault(v); ok {
value, err := decode(def)
if err != nil {
return f.errorf("default: %w", err)
}
f.defaultValue = value
f.hasDefault = true
}
if raw, ok := nixAttrs["default"]; ok {
value, err := parseNixDefault(v, f, raw)
if err != nil {
return f.errorf("@nix(default=%s): %w", raw, err)
}
f.nixDefault = value
f.hasNixDefault = true
}
return nil
}
// parseNixDefault parses the value of @nix(default=...) and checks it against the schema.
// For string fields the raw text is the value, otherwise it's parsed as CUE.
func parseNixDefault(v cue.Value, f *field, raw string) (any, error) {
var def cue.Value
if !f.isList && f.scalar.kind == kindString {
def = v.Context().Encode(raw)
} else {
def = v.Context().CompileString(raw)
}
if err := def.Err(); err != nil {
return nil, err
}
unified := v.Unify(def)
if err := unified.Validate(cue.Concrete(true)); err != nil {
return nil, err
}
return decode(unified)
}
// listElem returns the element type of an open list ([...T]), or a non-existent value if v isn't one.
//
// v may be wrapped, or be a disjunction such as [...int] | *[1, 2] when the list has a default,
// so up to a few layers are looked through to find the list.
func listElem(v cue.Value) cue.Value {
anyIndex := cue.MakePath(cue.AnyIndex)
for range 4 {
if elem := v.LookupPath(anyIndex); elem.Exists() {
return elem
}
op, args := v.Expr()
switch {
case op == cue.NoOp && len(args) == 1:
v = args[0]
case op == cue.OrOp:
// Only one side of the disjunction may be an open list
var elems []cue.Value
for _, arg := range args {
if elem := arg.LookupPath(anyIndex); elem.Exists() {
elems = append(elems, elem)
}
}
if len(elems) != 1 {
return cue.Value{}
}
return elems[0]
default:
return cue.Value{}
}
}
return cue.Value{}
}
// concreteDefault returns v's default, or v itself if it's already a concrete value
func concreteDefault(v cue.Value) (cue.Value, bool) {
if def, ok := v.Default(); ok && def.IsConcrete() {
return def, true
}
if v.IsConcrete() && v.Validate(cue.Concrete(true)) == nil {
return v, true
}
return cue.Value{}, false
}
// buildScalar builds the scalar for v, along with its constraints.
//
// @go and @nix attributes are also read from any definitions v references (e.g. #Duration).
// fieldGoAttrs are the field's own @go attributes, which win over those of the definitions.
func (b *builder) buildScalar(v cue.Value, fieldGoAttrs map[string]string) (scalar, error) {
var s scalar
switch k := v.IncompleteKind(); k {
case cue.BoolKind:
s.kind = kindBool
case cue.IntKind:
s.kind = kindInt
case cue.FloatKind:
s.kind = kindFloat
case cue.NumberKind:
s.kind = kindNumber
case cue.StringKind:
s.kind = kindString
default:
return s, fmt.Errorf("unsupported type %v", k)
}
var c constraints
if err := c.collect(v, "", 0); err != nil {
return s, err
}
s.min = c.min
s.max = c.max
for _, re := range c.regexes {
sr := scalarRegex{pattern: re.pattern}
if re.definition != "" {
// A definition that can't be a Go name just falls back to the field's name
sr.goName, _ = b.names.fieldName(re.definition)
}
s.regexes = append(s.regexes, sr)
}
s.notEmpty = c.notEmpty
for _, e := range c.enum {
value, err := decode(e)
if err != nil {
return s, err
}
s.enum = append(s.enum, value)
}
goAttrs := make(map[string]string)
maps.Copy(goAttrs, fieldGoAttrs)
// Definitions are nearest first, so the first one to set an attribute wins
for _, def := range c.definitions {
defGoAttrs, err := readAttrs(def, "go", "type", "parse", "import")
if err != nil {
return s, err
}
defNixAttrs, err := readAttrs(def, "nix", "type", "apply", "import")
if err != nil {
return s, err
}
for key, val := range defGoAttrs {
if _, ok := goAttrs[key]; !ok {
goAttrs[key] = val
}
}
if s.nixType == "" {
s.nixType = defNixAttrs["type"]
}
if s.nixApply == "" {
s.nixApply = defNixAttrs["apply"]
}
s.nixImports = append(s.nixImports, strings.Fields(defNixAttrs["import"])...)
}
s.goType = goAttrs["type"]
s.goParse = goAttrs["parse"]
if (s.goType == "") != (s.goParse == "") {
return s, errors.New("@go(type) and @go(parse) must be set together")
}
s.goImports = strings.Fields(goAttrs["import"])
return s, nil
}
// readAttrs returns the key=value arguments of the @name(...) attribute on v, or nil if there isn't one.
// A key without a value, such as @nix(skip), maps to an empty string. Any key not in known is an error.
func readAttrs(v cue.Value, name string, known ...string) (map[string]string, error) {
attr := v.Attribute(name)
if attr.Err() != nil {
return nil, nil
}
attrs := make(map[string]string)
for idx := range attr.NumArgs() {
key, val := attr.Arg(idx)
key = strings.TrimSpace(key)
if !slices.Contains(known, key) {
return nil, fmt.Errorf("unknown key %q in @%s (known: %s)", key, name, strings.Join(slices.Sorted(slices.Values(known)), ", "))
}
attrs[key] = strings.TrimSpace(val)
}
return attrs, nil
}
// docText returns v's doc comments, one paragraph per comment group
func docText(v cue.Value) string {
var paragraphs []string
for _, group := range v.Doc() {
if text := strings.TrimSpace(group.Text()); text != "" {
paragraphs = append(paragraphs, text)
}
}
return strings.Join(paragraphs, "\n\n")
}
// decode converts a concrete CUE value to a Go value, keeping numbers as json.Number so they print as written
func decode(v cue.Value) (any, error) {
data, err := v.MarshalJSON()
if err != nil {
return nil, err
}
dec := json.NewDecoder(bytes.NewReader(data))
dec.UseNumber()
var out any
if err := dec.Decode(&out); err != nil {
return nil, err
}
return out, nil
}
// valueString returns a decoded value as plain text, e.g. for usage and error messages
func valueString(v any) string {
switch v := v.(type) {
case string:
return v
case json.Number:
return v.String()
default:
return fmt.Sprint(v)
}
}
// pathString returns path as a flag name, or (root) for the root struct
func pathString(path []string) string {
if len(path) == 0 {
return "(root)"
}
return strings.Join(path, ".")
}
|