lang: funcs: Move standalone functions into core
Everything should be all together.
This commit is contained in:
James Shubin
317
lang/core/struct_lookup_optional.go
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317
lang/core/struct_lookup_optional.go
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// Mgmt
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// Copyright (C) 2013-2024+ James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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//
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// Additional permission under GNU GPL version 3 section 7
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//
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// If you modify this program, or any covered work, by linking or combining it
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// with embedded mcl code and modules (and that the embedded mcl code and
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// modules which link with this program, contain a copy of their source code in
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// the authoritative form) containing parts covered by the terms of any other
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// license, the licensors of this program grant you additional permission to
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// convey the resulting work. Furthermore, the licensors of this program grant
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// the original author, James Shubin, additional permission to update this
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// additional permission if he deems it necessary to achieve the goals of this
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// additional permission.
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package core
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import (
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"context"
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"fmt"
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"github.com/purpleidea/mgmt/lang/funcs"
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"github.com/purpleidea/mgmt/lang/interfaces"
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"github.com/purpleidea/mgmt/lang/types"
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"github.com/purpleidea/mgmt/util/errwrap"
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)
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const (
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// StructLookupOptionalFuncName is the name this function is registered
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// as. This starts with an underscore so that it cannot be used from the
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// lexer.
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StructLookupOptionalFuncName = funcs.StructLookupOptionalFuncName
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// arg names...
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structLookupOptionalArgNameStruct = "struct"
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structLookupOptionalArgNameField = "field"
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structLookupOptionalArgNameOptional = "optional"
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)
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func init() {
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funcs.Register(StructLookupOptionalFuncName, func() interfaces.Func { return &StructLookupOptionalFunc{} }) // must register the func and name
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}
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var _ interfaces.InferableFunc = &StructLookupOptionalFunc{} // ensure it meets this expectation
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// StructLookupOptionalFunc is a struct field lookup function. It does a special
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// trick in that it will unify on a struct that doesn't have the specified field
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// in it, but in that case, it will always return the optional value. This is a
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// bit different from the "default" mechanism that is used by list and map
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// lookup functions.
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type StructLookupOptionalFunc struct {
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Type *types.Type // Kind == Struct, that is used as the struct we lookup
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Out *types.Type // type of field we're extracting (also the type of optional)
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built bool // was this function built yet?
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init *interfaces.Init
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last types.Value // last value received to use for diff
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field string
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result types.Value // last calculated output
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}
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// String returns a simple name for this function. This is needed so this struct
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// can satisfy the pgraph.Vertex interface.
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func (obj *StructLookupOptionalFunc) String() string {
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return StructLookupOptionalFuncName
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}
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// ArgGen returns the Nth arg name for this function.
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func (obj *StructLookupOptionalFunc) ArgGen(index int) (string, error) {
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seq := []string{structLookupOptionalArgNameStruct, structLookupOptionalArgNameField, structLookupOptionalArgNameOptional}
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if l := len(seq); index >= l {
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return "", fmt.Errorf("index %d exceeds arg length of %d", index, l)
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}
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return seq[index], nil
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}
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// helper
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func (obj *StructLookupOptionalFunc) sig() *types.Type {
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st := "?1"
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out := "?2"
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if obj.Type != nil {
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st = obj.Type.String()
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}
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if obj.Out != nil {
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out = obj.Out.String()
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}
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return types.NewType(fmt.Sprintf(
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"func(%s %s, %s str, %s %s) %s",
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structLookupOptionalArgNameStruct, st,
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structLookupOptionalArgNameField,
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structLookupOptionalArgNameOptional, out,
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out,
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))
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}
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// FuncInfer takes partial type and value information from the call site of this
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// function so that it can build an appropriate type signature for it. The type
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// signature may include unification variables.
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func (obj *StructLookupOptionalFunc) FuncInfer(partialType *types.Type, partialValues []types.Value) (*types.Type, []*interfaces.UnificationInvariant, error) {
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// func(struct ?1, field str, optional ?2) ?2
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// This particular function should always get called with a known string
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// for the second argument. Without it being known statically, we refuse
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// to build this function.
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if l := 3; len(partialValues) != l {
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return nil, nil, fmt.Errorf("function must have %d args", l)
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}
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if err := partialValues[1].Type().Cmp(types.TypeStr); err != nil {
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return nil, nil, errwrap.Wrapf(err, "function field name must be a str")
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}
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s := partialValues[1].Str() // must not panic
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if s == "" {
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return nil, nil, fmt.Errorf("function must not have an empty field name")
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}
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// This can happen at runtime too, but we save it here for Build()!
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//obj.field = s // don't store for this optional lookup version!
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// Figure out more about the sig if any information is known statically.
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if len(partialType.Ord) > 0 && partialType.Map[partialType.Ord[0]] != nil {
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obj.Type = partialType.Map[partialType.Ord[0]] // assume this
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if obj.Type.Kind == types.KindStruct && obj.Type.Map != nil {
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if typ, exists := obj.Type.Map[s]; exists {
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obj.Out = typ
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}
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}
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}
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// This isn't precise enough because we must guarantee that the field is
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// in the struct and that ?1 is actually a struct, but that's okay it is
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// something that we'll verify at build time! (Or skip it for optional!)
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return obj.sig(), []*interfaces.UnificationInvariant{}, nil
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}
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// Build is run to turn the polymorphic, undetermined function, into the
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// specific statically typed version. It is usually run after Unify completes,
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// and must be run before Info() and any of the other Func interface methods are
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// used. This function is idempotent, as long as the arg isn't changed between
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// runs.
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func (obj *StructLookupOptionalFunc) Build(typ *types.Type) (*types.Type, error) {
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// typ is the KindFunc signature we're trying to build...
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if typ.Kind != types.KindFunc {
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return nil, fmt.Errorf("input type must be of kind func")
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}
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if len(typ.Ord) != 3 {
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return nil, fmt.Errorf("the structlookup function needs exactly three args")
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}
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if typ.Out == nil {
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return nil, fmt.Errorf("return type of function must be specified")
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}
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if typ.Map == nil {
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return nil, fmt.Errorf("invalid input type")
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}
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tStruct, exists := typ.Map[typ.Ord[0]]
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if !exists || tStruct == nil {
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return nil, fmt.Errorf("first arg must be specified")
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}
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tField, exists := typ.Map[typ.Ord[1]]
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if !exists || tField == nil {
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return nil, fmt.Errorf("second arg must be specified")
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}
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if err := tField.Cmp(types.TypeStr); err != nil {
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return nil, errwrap.Wrapf(err, "field must be an str")
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}
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tOptional, exists := typ.Map[typ.Ord[2]]
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if !exists || tOptional == nil {
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return nil, fmt.Errorf("third arg must be specified")
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}
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if err := tOptional.Cmp(typ.Out); err != nil {
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return nil, errwrap.Wrapf(err, "optional arg must match return type")
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}
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// NOTE: We actually don't know which field this is yet, only its type!
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// We don't care, because that's a runtime issue and doesn't need to be
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// our problem as long as this is a struct. The only optimization we can
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// add is to know statically if we're returning the optional value.
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if tStruct.Kind != types.KindStruct {
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return nil, fmt.Errorf("first arg must be of kind struct, got: %s", tStruct.Kind)
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}
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obj.Type = tStruct // struct type
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obj.Out = typ.Out // type of return value
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obj.built = true
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return obj.sig(), nil
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}
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// Validate tells us if the input struct takes a valid form.
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func (obj *StructLookupOptionalFunc) Validate() error {
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if !obj.built {
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return fmt.Errorf("function wasn't built yet")
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}
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if obj.Type == nil { // build must be run first
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return fmt.Errorf("type is still unspecified")
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}
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if obj.Type.Kind != types.KindStruct {
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return fmt.Errorf("type must be a kind of struct")
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}
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if obj.Out == nil {
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return fmt.Errorf("return type must be specified")
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}
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// TODO: can we do better and validate more aspects here?
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return nil
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}
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// Info returns some static info about itself. Build must be called before this
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// will return correct data.
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func (obj *StructLookupOptionalFunc) Info() *interfaces.Info {
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// Since this function implements FuncInfer we want sig to return nil to
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// avoid an accidental return of unification variables when we should be
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// getting them from FuncInfer, and not from here. (During unification!)
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var sig *types.Type
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if obj.built {
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sig = obj.sig() // helper
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}
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return &interfaces.Info{
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Pure: true,
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Memo: false,
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Sig: sig,
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Err: obj.Validate(),
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}
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}
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// Init runs some startup code for this function.
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func (obj *StructLookupOptionalFunc) Init(init *interfaces.Init) error {
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obj.init = init
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return nil
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}
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// Stream returns the changing values that this func has over time.
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func (obj *StructLookupOptionalFunc) Stream(ctx context.Context) error {
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defer close(obj.init.Output) // the sender closes
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for {
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select {
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case input, ok := <-obj.init.Input:
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if !ok {
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return nil // can't output any more
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}
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//if err := input.Type().Cmp(obj.Info().Sig.Input); err != nil {
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// return errwrap.Wrapf(err, "wrong function input")
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//}
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if obj.last != nil && input.Cmp(obj.last) == nil {
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continue // value didn't change, skip it
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}
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obj.last = input // store for next
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st := (input.Struct()[structLookupOptionalArgNameStruct]).(*types.StructValue)
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field := input.Struct()[structLookupOptionalArgNameField].Str()
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optional := input.Struct()[structLookupOptionalArgNameOptional]
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if field == "" {
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return fmt.Errorf("received empty field")
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}
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if obj.field == "" {
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// This can happen at compile time too. Bonus!
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obj.field = field // store first field
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}
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if field != obj.field {
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return fmt.Errorf("input field changed from: `%s`, to: `%s`", obj.field, field)
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}
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// We know the result of this lookup statically at
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// compile time, but for simplicity we check each time
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// here anyways. Maybe one day there will be a fancy
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// reason why this might vary over time.
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var result types.Value
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val, exists := st.Lookup(obj.field)
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if exists {
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result = val
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} else {
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result = optional
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}
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// if previous input was `2 + 4`, but now it
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// changed to `1 + 5`, the result is still the
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// same, so we can skip sending an update...
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if obj.result != nil && result.Cmp(obj.result) == nil {
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continue // result didn't change
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}
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obj.result = result // store new result
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case <-ctx.Done():
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return nil
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}
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select {
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case obj.init.Output <- obj.result: // send
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case <-ctx.Done():
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return nil
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}
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}
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}
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