lang: funcs: Move standalone functions into core
Everything should be all together.
This commit is contained in:
James Shubin
338
lang/core/struct_lookup.go
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338
lang/core/struct_lookup.go
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@@ -0,0 +1,338 @@
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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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// StructLookupFuncName is the name this function is registered as. This
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// starts with an underscore so that it cannot be used from the lexer.
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StructLookupFuncName = funcs.StructLookupFuncName
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// arg names...
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structLookupArgNameStruct = "struct"
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structLookupArgNameField = "field"
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)
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func init() {
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funcs.Register(StructLookupFuncName, func() interfaces.Func { return &StructLookupFunc{} }) // must register the func and name
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}
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var _ interfaces.BuildableFunc = &StructLookupFunc{} // ensure it meets this expectation
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// StructLookupFunc is a struct field lookup function.
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type StructLookupFunc 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
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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 *StructLookupFunc) String() string {
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return StructLookupFuncName
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}
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// ArgGen returns the Nth arg name for this function.
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func (obj *StructLookupFunc) ArgGen(index int) (string, error) {
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seq := []string{structLookupArgNameStruct, structLookupArgNameField}
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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 *StructLookupFunc) 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",
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structLookupArgNameStruct, st,
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structLookupArgNameField,
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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 *StructLookupFunc) FuncInfer(partialType *types.Type, partialValues []types.Value) (*types.Type, []*interfaces.UnificationInvariant, error) {
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// func(struct ?1, field str) ?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 := 2; 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 // store for later
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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!
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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 *StructLookupFunc) 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) != 2 {
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return nil, fmt.Errorf("the structlookup function needs exactly two 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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// NOTE: We actually don't know which field this is yet, only its type!
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// We cached the discovered field during Infer(), but it turns out it's
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// not actually necessary for us to know it to build the struct. It is
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// needed to make sure the lossy Infer unification variables are right.
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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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if obj.field == "" {
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// programming error
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return nil, fmt.Errorf("did not infer correctly")
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}
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ix := -1 // not found
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for i, x := range tStruct.Ord {
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if x != obj.field {
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continue
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}
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// found
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if ix != -1 {
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// programming error
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return nil, fmt.Errorf("duplicate field found")
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}
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ix = i // found it here!
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//break // keep checking for extra safety
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}
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if ix == -1 {
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return nil, fmt.Errorf("field %s was not found in struct", obj.field)
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}
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tF, exists := tStruct.Map[tStruct.Ord[ix]]
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if !exists {
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return nil, fmt.Errorf("field %s was not found in struct", obj.field)
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}
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// The return value must match the type of the field we're pulling out!
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if err := typ.Out.Cmp(tF); err != nil {
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return nil, fmt.Errorf("field %s type error: %+v", obj.field, err)
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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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// Copy is implemented so that the obj.field value is not lost if we copy this
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// function. That value is learned during FuncInfer, and previously would have
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// been lost by the time we used it in Build.
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func (obj *StructLookupFunc) Copy() interfaces.Func {
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return &StructLookupFunc{
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Type: obj.Type, // don't copy because we use this after unification
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Out: obj.Out,
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built: obj.built,
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init: obj.init, // likely gets overwritten anyways
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field: obj.field, // this we really need!
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}
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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 *StructLookupFunc) 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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for _, t := range obj.Type.Map {
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if obj.Out.Cmp(t) == nil {
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return nil // found at least one match
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}
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}
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return fmt.Errorf("return type is not in the list of available struct fields")
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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 *StructLookupFunc) 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 *StructLookupFunc) 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 *StructLookupFunc) 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()[structLookupArgNameStruct]).(*types.StructValue)
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field := input.Struct()[structLookupArgNameField].Str()
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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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result, exists := st.Lookup(obj.field)
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if !exists {
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return fmt.Errorf("could not lookup field: `%s` in struct", field)
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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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