lang: Move the Edge struct into the interfaces package

This makes it consumable from more than one package and avoids future
cycles.

lang/ast/structs.go

@@ -5508,7 +5508,7 @@ func (obj *ExprList) Graph() (*pgraph.Graph, error) {
 		}
 
 		fieldName := fmt.Sprintf("%d", index) // argNames as integers!
-		edge := &funcs.Edge{Args: []string{fieldName}}
+		edge := &interfaces.FuncEdge{Args: []string{fieldName}}
 
 		var once bool
 		edgeGenFn := func(v1, v2 pgraph.Vertex) pgraph.Edge {
@@ -5984,7 +5984,7 @@ func (obj *ExprMap) Graph() (*pgraph.Graph, error) {
 		}
 		// do the key names ever change? -- yes
 		fieldName := fmt.Sprintf("key:%d", index) // stringify map key
-		edge := &funcs.Edge{Args: []string{fieldName}}
+		edge := &interfaces.FuncEdge{Args: []string{fieldName}}
 
 		var once bool
 		edgeGenFn := func(v1, v2 pgraph.Vertex) pgraph.Edge {
@@ -6004,7 +6004,7 @@ func (obj *ExprMap) Graph() (*pgraph.Graph, error) {
 			return nil, err
 		}
 		fieldName := fmt.Sprintf("val:%d", index) // stringify map val
-		edge := &funcs.Edge{Args: []string{fieldName}}
+		edge := &interfaces.FuncEdge{Args: []string{fieldName}}
 
 		var once bool
 		edgeGenFn := func(v1, v2 pgraph.Vertex) pgraph.Edge {
@@ -6396,7 +6396,7 @@ func (obj *ExprStruct) Graph() (*pgraph.Graph, error) {
 		}
 
 		fieldName := x.Name
-		edge := &funcs.Edge{Args: []string{fieldName}}
+		edge := &interfaces.FuncEdge{Args: []string{fieldName}}
 
 		var once bool
 		edgeGenFn := func(v1, v2 pgraph.Vertex) pgraph.Edge {
@@ -7209,7 +7209,7 @@ func (obj *ExprFunc) Graph() (*pgraph.Graph, error) {
 		// when we add an edge from this, then we'll get two because the
 		// contents aren't linked.
 		name := "body" // TODO: what should we name this?
-		edge := &funcs.Edge{Args: []string{name}}
+		edge := &interfaces.FuncEdge{Args: []string{name}}
 
 		var once bool
 		edgeGenFn := func(v1, v2 pgraph.Vertex) pgraph.Edge {
@@ -8221,9 +8221,9 @@ func (obj *ExprCall) Graph() (*pgraph.Graph, error) {
 
 		//argName := fmt.Sprintf("%d", pos) // indexed!
 		argName := argNames[pos]
-		edge := &funcs.Edge{Args: []string{argName}}
+		edge := &interfaces.FuncEdge{Args: []string{argName}}
 		// TODO: replace with:
-		//edge := &funcs.Edge{Args: []string{fmt.Sprintf("arg:%s", argName)}}
+		//edge := &interfaces.FuncEdge{Args: []string{fmt.Sprintf("arg:%s", argName)}}
 
 		var once bool
 		edgeGenFn := func(v1, v2 pgraph.Vertex) pgraph.Edge {
@@ -8253,7 +8253,7 @@ func (obj *ExprCall) Graph() (*pgraph.Graph, error) {
 		return nil, err
 	}
 
-	edge := &funcs.Edge{Args: []string{fmt.Sprintf("call:%s", obj.Name)}}
+	edge := &interfaces.FuncEdge{Args: []string{fmt.Sprintf("call:%s", obj.Name)}}
 
 	var once bool
 	edgeGenFn := func(v1, v2 pgraph.Vertex) pgraph.Edge {
@@ -8536,7 +8536,7 @@ func (obj *ExprVar) Graph() (*pgraph.Graph, error) {
 		return nil, err
 	}
 
-	edge := &funcs.Edge{Args: []string{fmt.Sprintf("var:%s", obj.Name)}}
+	edge := &interfaces.FuncEdge{Args: []string{fmt.Sprintf("var:%s", obj.Name)}}
 
 	var once bool
 	edgeGenFn := func(v1, v2 pgraph.Vertex) pgraph.Edge {
@@ -8949,7 +8949,7 @@ func (obj *ExprIf) Graph() (*pgraph.Graph, error) {
 			return nil, err
 		}
 
-		edge := &funcs.Edge{Args: []string{argName}}
+		edge := &interfaces.FuncEdge{Args: []string{argName}}
 
 		var once bool
 		edgeGenFn := func(v1, v2 pgraph.Vertex) pgraph.Edge {

lang/funcs/engine.go

@@ -19,7 +19,6 @@ package funcs
 
 import (
 	"fmt"
-	"strings"
 	"sync"
 
 	"github.com/purpleidea/mgmt/engine"
@@ -86,17 +85,6 @@ func (obj *State) String() string {
 	return obj.Expr.String()
 }
 
-// Edge links an output vertex (value) to an input vertex with a named argument.
-type Edge struct {
-	Args []string // list of named args that this edge sends to
-}
-
-// String displays the list of arguments this edge satisfies. It is a required
-// property to be a valid pgraph.Edge.
-func (obj *Edge) String() string {
-	return strings.Join(obj.Args, ", ")
-}
-
 // Engine represents the running time varying directed acyclic function graph.
 type Engine struct {
 	Graph    *pgraph.Graph
@@ -205,7 +193,7 @@ func (obj *Engine) Validate() error {
 		ptrs = append(ptrs, node.handle)
 	}
 	for _, edge := range obj.Graph.Edges() {
-		if _, ok := edge.(*Edge); !ok {
+		if _, ok := edge.(*interfaces.FuncEdge); !ok {
 			e := fmt.Errorf("edge `%s` was not the correct type", edge)
 			err = errwrap.Append(err, e)
 		}
@@ -250,7 +238,7 @@ func (obj *Engine) Validate() error {
 		node1 := obj.state[vertex1]
 		for vertex2, edge := range obj.Graph.Adjacency()[vertex1] {
 			node2 := obj.state[vertex2]
-			edge := edge.(*Edge)
+			edge := edge.(*interfaces.FuncEdge)
 			// check vertex1 -> vertex2 (with e) is valid
 
 			for _, arg := range edge.Args { // loop over each arg
@@ -378,7 +366,7 @@ func (obj *Engine) Run() error {
 					}
 					st := types.NewStruct(si)
 					for _, v := range incoming {
-						args := obj.Graph.Adjacency()[v][vertex].(*Edge).Args
+						args := obj.Graph.Adjacency()[v][vertex].(*interfaces.FuncEdge).Args
 						from := obj.state[v]
 						obj.mutex.RLock()
 						value, exists := obj.table[v]

lang/interfaces/func.go

@@ -18,6 +18,8 @@
 package interfaces
 
 import (
+	"strings"
+
 	"github.com/purpleidea/mgmt/engine"
 	"github.com/purpleidea/mgmt/lang/types"
 )
@@ -187,3 +189,15 @@ type DataFunc interface {
 	// context.
 	SetData(*FuncData)
 }
+
+// FuncEdge links an output vertex (value) to an input vertex with a named
+// argument.
+type FuncEdge struct {
+	Args []string // list of named args that this edge sends to
+}
+
+// String displays the list of arguments this edge satisfies. It is a required
+// property to be a valid pgraph.Edge.
+func (obj *FuncEdge) String() string {
+	return strings.Join(obj.Args, ", ")
+}