starlark/typed/dict.go - infra/luci/luci-go - Git at Google

 // Copyright 2019 The LUCI 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
 //
 //      http://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 typed

 import (
 	"fmt"

 	"go.starlark.net/starlark"
 	"go.starlark.net/syntax"
 )

 // Dict is a Starlark value that looks like a regular dict, but implements type
 // checks and implicit conversions for keys and values when assigning elements.
 //
 // Note that keys(), values() and items() methods return regular lists, not
 // typed ones.
 //
 // Differences from regular dicts:
 //   - Not comparable by value to regular dicts, only to other typed dicts.
 //     go.starlark.net has no way to express that typed dicts should be
 //     comparable to regular dicts.
 //   - update() doesn't support keyword arguments. Using keyword arguments
 //     implies string keys which make no sense in generic typed Dict interface,
 //     since generally strings are not valid keys. This also substantially
 //     simplifies the implementation of update().
 type Dict struct {
 	keyT Converter      // defines the type of keys
 	valT Converter      // defines the type of values
 	dict *starlark.Dict // the underlying untyped dict
 }

 // Note that these interfaces intersect, so we can't mush them into a single
 // interface to check *Dict conforms it.
 var (
 	_ starlark.Value           = (*Dict)(nil)
 	_ starlark.Sequence        = (*Dict)(nil)
 	_ starlark.IterableMapping = (*Dict)(nil)
 	_ starlark.HasAttrs        = (*Dict)(nil)
 	_ starlark.HasSetKey       = (*Dict)(nil)
 	_ starlark.Comparable      = (*Dict)(nil)
 )

 // NewDict returns a dict with give preallocated capacity.
 func NewDict(key, val Converter, size int) *Dict {
 	return &Dict{
 		keyT: key,
 		valT: val,
 		dict: starlark.NewDict(size),
 	}
 }

 // AsTypedDict allocates a new dict<k,v>, and copies it from 'x'.
 //
 // Returns an error if 'x' is not an iterable mapping or some of its (k, v)
 // pairs can't be converted to requested types.
 func AsTypedDict(k, v Converter, x starlark.Value) (*Dict, error) {
 	m, ok := x.(starlark.IterableMapping)
 	if !ok {
 		return nil, fmt.Errorf("got %s, want an iterable mapping", x.Type())
 	}
 	items := m.Items()
 	d := NewDict(k, v, len(items))
 	for _, kv := range items {
 		if err := d.SetKey(kv[0], kv[1]); err != nil {
 			return nil, err
 		}
 	}
 	return d, nil
 }

 // KeyConverter returns the type converter used for keys of this dict.
 func (d *Dict) KeyConverter() Converter { return d.keyT }

 // ValueConverter returns the type converter used for values of this dict.
 func (d *Dict) ValueConverter() Converter { return d.valT }

 // conv calls Convert on a (k, v) pair, annotating the error.
 func (d *Dict) conv(k, v starlark.Value) (starlark.Value, starlark.Value, error) {
 	var err error
 	k, err = d.keyT.Convert(k)
 	if err != nil {
 		return nil, nil, fmt.Errorf("bad key: %s", err)
 	}
 	v, err = d.valT.Convert(v)
 	if err != nil {
 		return nil, nil, fmt.Errorf("bad value: %s", err)
 	}
 	return k, v, nil
 }

 // starlark.Dict methods we reimplement or proxy.

 func (d *Dict) Type() string {
 	return fmt.Sprintf("dict<%s,%s>", d.keyT.Type(), d.valT.Type())
 }

 func (d *Dict) String() string {
 	return fmt.Sprintf("%s(%s)", d.Type(), d.dict.String())
 }

 func (d *Dict) Hash() (uint32, error) {
 	return 0, fmt.Errorf("unhashable type: %s", d.Type())
 }

 func (d *Dict) SetKey(k, v starlark.Value) error {
 	k, v, err := d.conv(k, v)
 	if err != nil {
 		return err
 	}
 	return d.dict.SetKey(k, v)
 }

 func (d *Dict) AttrNames() []string {
 	// Note: we hardcode the list of methods (rather than call d.dict.AttrNames)
 	// to be able to notice (via the failing test) when go.starlark.net adds some
 	// new methods that we might need to "wrap" in Attr(...).
 	return []string{
 		"clear",
 		"get",
 		"items",
 		"keys",
 		"pop",
 		"popitem",
 		"setdefault",
 		"update",
 		"values",
 	}
 }

 func (d *Dict) Attr(name string) (starlark.Value, error) {
 	switch name {
 	case "setdefault":
 		return d.implSetDefault(), nil
 	case "update":
 		return d.implUpdate(), nil
 	default:
 		return d.dict.Attr(name)
 	}
 }

 func (d *Dict) CompareSameType(op syntax.Token, y starlark.Value, depth int) (bool, error) {
 	switch op {
 	case syntax.EQL:
 		return dictsEqual(d, y.(*Dict), depth)
 	case syntax.NEQ:
 		eq, err := dictsEqual(d, y.(*Dict), depth)
 		return !eq, err
 	default:
 		return false, fmt.Errorf("%q is not implemented for %s", op, d.Type())
 	}
 }

 func dictsEqual(l, r *Dict, depth int) (bool, error) {
 	if l.keyT != r.keyT || l.valT != r.valT {
 		return false, nil
 	}
 	return l.dict.CompareSameType(syntax.EQL, r.dict, depth)
 }

 // starlark.Dict methods delegated without any modifications.

 func (d *Dict) Clear() error                                                   { return d.dict.Clear() }
 func (d *Dict) Delete(k starlark.Value) (starlark.Value, bool, error)          { return d.dict.Delete(k) }
 func (d *Dict) Get(k starlark.Value) (v starlark.Value, found bool, err error) { return d.dict.Get(k) }
 func (d *Dict) Items() []starlark.Tuple                                        { return d.dict.Items() }
 func (d *Dict) Keys() []starlark.Value                                         { return d.dict.Keys() }
 func (d *Dict) Len() int                                                       { return d.dict.Len() }
 func (d *Dict) Iterate() starlark.Iterator                                     { return d.dict.Iterate() }
 func (d *Dict) Freeze()                                                        { d.dict.Freeze() }
 func (d *Dict) Truth() starlark.Bool                                           { return d.dict.Truth() }

 // Reimplemented builtins.

 // implSetDefault reimplements 'setdefault' via Get and SetKey.
 func (d *Dict) implSetDefault() *starlark.Builtin {
 	return starlark.NewBuiltin("setdefault", func(th *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
 		var key, dflt starlark.Value = nil, starlark.None
 		if err := starlark.UnpackPositionalArgs("setdefault", args, kwargs, 1, &key, &dflt); err != nil {
 			return nil, err
 		}

 		// Convert first to avoid "lazy" type checking for 'dflt'.
 		key, dflt, err := d.conv(key, dflt)
 		if err != nil {
 			return nil, fmt.Errorf("setdefault: %s", err)
 		}

 		// Do regular d.dict.setdefault(...) logic.
 		if v, ok, err := d.dict.Get(key); err != nil {
 			return nil, fmt.Errorf("setdefault: %s", err)
 		} else if ok {
 			return v, nil
 		} else if err := d.dict.SetKey(key, dflt); err != nil {
 			return nil, fmt.Errorf("setdefault: %s", err)
 		} else {
 			return dflt, nil
 		}
 	})
 }

 // implUpdate reimplements 'update' via SetKey(...).
 //
 // This is a simplified version that doesn't accept kwargs, since generally
 // their stringy keys make no sense for typed dicts.
 func (d *Dict) implUpdate() *starlark.Builtin {
 	return starlark.NewBuiltin("update", func(th *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
 		switch {
 		case len(kwargs) > 0:
 			return nil, fmt.Errorf("update: got unexpected keyword argument")
 		case len(args) != 1:
 			return nil, fmt.Errorf("update: got %d arguments, want exactly 1", len(args))
 		}
 		v := args[0]

 		// Fastest path: adding items from a typed dict with the exact same
 		// signature: can just directly update the dict skipping the conversion.
 		if td, ok := v.(*Dict); ok && td.keyT == d.keyT && td.valT == d.valT {
 			for i, item := range td.dict.Items() {
 				if err := d.dict.SetKey(item[0], item[1]); err != nil {
 					return nil, fmt.Errorf("update: element #%d: %s", i, err)
 				}
 			}
 			return starlark.None, nil
 		}

 		// Fast path: adding items from an IterableMapping (e.g. a regular dict).
 		// Need to convert (k, v) by passing them through the converter in SetKey.
 		if im, ok := v.(starlark.IterableMapping); ok {
 			for i, item := range im.Items() {
 				if err := d.SetKey(item[0], item[1]); err != nil {
 					return nil, fmt.Errorf("update: element #%d: %s", i, err)
 				}
 			}
 			return starlark.None, nil
 		}

 		// Slow generic path: an iterable with (k,v) pairs (represented by iterables
 		// themselves).
 		iter := starlark.Iterate(v)
 		if iter == nil {
 			return nil, fmt.Errorf("update: got %s, want iterable", v.Type())
 		}
 		defer iter.Done()

 		var pair starlark.Value
 		for i := 0; iter.Next(&pair); i++ {
 			k, v, err := toKV(pair)
 			if err != nil {
 				return nil, fmt.Errorf("update: element #%d %s", i, err)
 			}
 			if err := d.SetKey(k, v); err != nil {
 				return nil, fmt.Errorf("update: element #%d: %s", i, err)
 			}
 		}

 		return starlark.None, nil
 	})
 }

 func toKV(pair starlark.Value) (k starlark.Value, v starlark.Value, err error) {
 	iter := starlark.Iterate(pair)
 	if iter == nil {
 		return nil, nil, fmt.Errorf("is not iterable (%s)", pair.Type())
 	}
 	defer iter.Done()

 	switch l := starlark.Len(pair); {
 	case l < 0:
 		return nil, nil, fmt.Errorf("has unknown length (%s)", pair.Type())
 	case l != 2:
 		return nil, nil, fmt.Errorf("has length %d, want 2", l)
 	}

 	// If len(...) == 2, iter MUST return 2 items.
 	if !iter.Next(&k) {
 		return nil, nil, fmt.Errorf("has bad iterable implementation (%s)", pair.Type())
 	}
 	if !iter.Next(&v) {
 		return nil, nil, fmt.Errorf("has bad iterable implementation (%s)", pair.Type())
 	}
 	return
 }
	// Copyright 2019 The LUCI 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
	//
	// http://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 typed

	import (
	"fmt"

	"go.starlark.net/starlark"
	"go.starlark.net/syntax"
	)

	// Dict is a Starlark value that looks like a regular dict, but implements type
	// checks and implicit conversions for keys and values when assigning elements.
	//
	// Note that keys(), values() and items() methods return regular lists, not
	// typed ones.
	//
	// Differences from regular dicts:
	// - Not comparable by value to regular dicts, only to other typed dicts.
	// go.starlark.net has no way to express that typed dicts should be
	// comparable to regular dicts.
	// - update() doesn't support keyword arguments. Using keyword arguments
	// implies string keys which make no sense in generic typed Dict interface,
	// since generally strings are not valid keys. This also substantially
	// simplifies the implementation of update().
	type Dict struct {
	keyT Converter // defines the type of keys
	valT Converter // defines the type of values
	dict *starlark.Dict // the underlying untyped dict
	}

	// Note that these interfaces intersect, so we can't mush them into a single
	// interface to check *Dict conforms it.
	var (
	_ starlark.Value = (*Dict)(nil)
	_ starlark.Sequence = (*Dict)(nil)
	_ starlark.IterableMapping = (*Dict)(nil)
	_ starlark.HasAttrs = (*Dict)(nil)
	_ starlark.HasSetKey = (*Dict)(nil)
	_ starlark.Comparable = (*Dict)(nil)
	)

	// NewDict returns a dict with give preallocated capacity.
	func NewDict(key, val Converter, size int) *Dict {
	return &Dict{
	keyT: key,
	valT: val,
	dict: starlark.NewDict(size),
	}
	}

	// AsTypedDict allocates a new dict<k,v>, and copies it from 'x'.
	//
	// Returns an error if 'x' is not an iterable mapping or some of its (k, v)
	// pairs can't be converted to requested types.
	func AsTypedDict(k, v Converter, x starlark.Value) (*Dict, error) {
	m, ok := x.(starlark.IterableMapping)
	if !ok {
	return nil, fmt.Errorf("got %s, want an iterable mapping", x.Type())
	}
	items := m.Items()
	d := NewDict(k, v, len(items))
	for _, kv := range items {
	if err := d.SetKey(kv[0], kv[1]); err != nil {
	return nil, err
	}
	}
	return d, nil
	}

	// KeyConverter returns the type converter used for keys of this dict.
	func (d *Dict) KeyConverter() Converter { return d.keyT }

	// ValueConverter returns the type converter used for values of this dict.
	func (d *Dict) ValueConverter() Converter { return d.valT }

	// conv calls Convert on a (k, v) pair, annotating the error.
	func (d *Dict) conv(k, v starlark.Value) (starlark.Value, starlark.Value, error) {
	var err error
	k, err = d.keyT.Convert(k)
	if err != nil {
	return nil, nil, fmt.Errorf("bad key: %s", err)
	}
	v, err = d.valT.Convert(v)
	if err != nil {
	return nil, nil, fmt.Errorf("bad value: %s", err)
	}
	return k, v, nil
	}

	// starlark.Dict methods we reimplement or proxy.

	func (d *Dict) Type() string {
	return fmt.Sprintf("dict<%s,%s>", d.keyT.Type(), d.valT.Type())
	}

	func (d *Dict) String() string {
	return fmt.Sprintf("%s(%s)", d.Type(), d.dict.String())
	}

	func (d *Dict) Hash() (uint32, error) {
	return 0, fmt.Errorf("unhashable type: %s", d.Type())
	}

	func (d *Dict) SetKey(k, v starlark.Value) error {
	k, v, err := d.conv(k, v)
	if err != nil {
	return err
	}
	return d.dict.SetKey(k, v)
	}

	func (d *Dict) AttrNames() []string {
	// Note: we hardcode the list of methods (rather than call d.dict.AttrNames)
	// to be able to notice (via the failing test) when go.starlark.net adds some
	// new methods that we might need to "wrap" in Attr(...).
	return []string{
	"clear",
	"get",
	"items",
	"keys",
	"pop",
	"popitem",
	"setdefault",
	"update",
	"values",
	}
	}

	func (d *Dict) Attr(name string) (starlark.Value, error) {
	switch name {
	case "setdefault":
	return d.implSetDefault(), nil
	case "update":
	return d.implUpdate(), nil
	default:
	return d.dict.Attr(name)
	}
	}

	func (d *Dict) CompareSameType(op syntax.Token, y starlark.Value, depth int) (bool, error) {
	switch op {
	case syntax.EQL:
	return dictsEqual(d, y.(*Dict), depth)
	case syntax.NEQ:
	eq, err := dictsEqual(d, y.(*Dict), depth)
	return !eq, err
	default:
	return false, fmt.Errorf("%q is not implemented for %s", op, d.Type())
	}
	}

	func dictsEqual(l, r *Dict, depth int) (bool, error) {
	if l.keyT != r.keyT \|\| l.valT != r.valT {
	return false, nil
	}
	return l.dict.CompareSameType(syntax.EQL, r.dict, depth)
	}

	// starlark.Dict methods delegated without any modifications.

	func (d *Dict) Clear() error { return d.dict.Clear() }
	func (d *Dict) Delete(k starlark.Value) (starlark.Value, bool, error) { return d.dict.Delete(k) }
	func (d *Dict) Get(k starlark.Value) (v starlark.Value, found bool, err error) { return d.dict.Get(k) }
	func (d *Dict) Items() []starlark.Tuple { return d.dict.Items() }
	func (d *Dict) Keys() []starlark.Value { return d.dict.Keys() }
	func (d *Dict) Len() int { return d.dict.Len() }
	func (d *Dict) Iterate() starlark.Iterator { return d.dict.Iterate() }
	func (d *Dict) Freeze() { d.dict.Freeze() }
	func (d *Dict) Truth() starlark.Bool { return d.dict.Truth() }

	// Reimplemented builtins.

	// implSetDefault reimplements 'setdefault' via Get and SetKey.
	func (d Dict) implSetDefault() starlark.Builtin {
	return starlark.NewBuiltin("setdefault", func(th starlark.Thread, _ starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
	var key, dflt starlark.Value = nil, starlark.None
	if err := starlark.UnpackPositionalArgs("setdefault", args, kwargs, 1, &key, &dflt); err != nil {
	return nil, err
	}

	// Convert first to avoid "lazy" type checking for 'dflt'.
	key, dflt, err := d.conv(key, dflt)
	if err != nil {
	return nil, fmt.Errorf("setdefault: %s", err)
	}

	// Do regular d.dict.setdefault(...) logic.
	if v, ok, err := d.dict.Get(key); err != nil {
	return nil, fmt.Errorf("setdefault: %s", err)
	} else if ok {
	return v, nil
	} else if err := d.dict.SetKey(key, dflt); err != nil {
	return nil, fmt.Errorf("setdefault: %s", err)
	} else {
	return dflt, nil
	}
	})
	}

	// implUpdate reimplements 'update' via SetKey(...).
	//
	// This is a simplified version that doesn't accept kwargs, since generally
	// their stringy keys make no sense for typed dicts.
	func (d Dict) implUpdate() starlark.Builtin {
	return starlark.NewBuiltin("update", func(th starlark.Thread, _ starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
	switch {
	case len(kwargs) > 0:
	return nil, fmt.Errorf("update: got unexpected keyword argument")
	case len(args) != 1:
	return nil, fmt.Errorf("update: got %d arguments, want exactly 1", len(args))
	}
	v := args[0]

	// Fastest path: adding items from a typed dict with the exact same
	// signature: can just directly update the dict skipping the conversion.
	if td, ok := v.(*Dict); ok && td.keyT == d.keyT && td.valT == d.valT {
	for i, item := range td.dict.Items() {
	if err := d.dict.SetKey(item[0], item[1]); err != nil {
	return nil, fmt.Errorf("update: element #%d: %s", i, err)
	}
	}
	return starlark.None, nil
	}

	// Fast path: adding items from an IterableMapping (e.g. a regular dict).
	// Need to convert (k, v) by passing them through the converter in SetKey.
	if im, ok := v.(starlark.IterableMapping); ok {
	for i, item := range im.Items() {
	if err := d.SetKey(item[0], item[1]); err != nil {
	return nil, fmt.Errorf("update: element #%d: %s", i, err)
	}
	}
	return starlark.None, nil
	}

	// Slow generic path: an iterable with (k,v) pairs (represented by iterables
	// themselves).
	iter := starlark.Iterate(v)
	if iter == nil {
	return nil, fmt.Errorf("update: got %s, want iterable", v.Type())
	}
	defer iter.Done()

	var pair starlark.Value
	for i := 0; iter.Next(&pair); i++ {
	k, v, err := toKV(pair)
	if err != nil {
	return nil, fmt.Errorf("update: element #%d %s", i, err)
	}
	if err := d.SetKey(k, v); err != nil {
	return nil, fmt.Errorf("update: element #%d: %s", i, err)
	}
	}

	return starlark.None, nil
	})
	}

	func toKV(pair starlark.Value) (k starlark.Value, v starlark.Value, err error) {
	iter := starlark.Iterate(pair)
	if iter == nil {
	return nil, nil, fmt.Errorf("is not iterable (%s)", pair.Type())
	}
	defer iter.Done()

	switch l := starlark.Len(pair); {
	case l < 0:
	return nil, nil, fmt.Errorf("has unknown length (%s)", pair.Type())
	case l != 2:
	return nil, nil, fmt.Errorf("has length %d, want 2", l)
	}

	// If len(...) == 2, iter MUST return 2 items.
	if !iter.Next(&k) {
	return nil, nil, fmt.Errorf("has bad iterable implementation (%s)", pair.Type())
	}
	if !iter.Next(&v) {
	return nil, nil, fmt.Errorf("has bad iterable implementation (%s)", pair.Type())
	}
	return
	}