terraform: subpath context setting

terraform/graph.go

@@ -144,8 +144,8 @@ func (g *Graph) init() {
 
 func (g *Graph) walk(walker GraphWalker) error {
 	// The callbacks for enter/exiting a graph
-	ctx := walker.EnterGraph(g)
-	defer walker.ExitGraph(g)
+	ctx := walker.EnterPath(g.Path)
+	defer walker.ExitPath(g.Path)
 
 	// Get the path for logs
 	path := strings.Join(ctx.Path(), ".")
@@ -158,6 +158,15 @@ func (g *Graph) walk(walker GraphWalker) error {
 		walker.EnterVertex(v)
 		defer func() { walker.ExitVertex(v, rerr) }()
 
+		// vertexCtx is the context that we use when evaluating. This
+		// is normally the context of our graph but can be overridden
+		// with a GraphNodeSubPath impl.
+		vertexCtx := ctx
+		if pn, ok := v.(GraphNodeSubPath); ok {
+			vertexCtx = walker.EnterPath(pn.Path())
+			defer walker.ExitPath(pn.Path())
+		}
+
 		// If the node is eval-able, then evaluate it.
 		if ev, ok := v.(GraphNodeEvalable); ok {
 			tree := ev.EvalTree()
@@ -170,7 +179,7 @@ func (g *Graph) walk(walker GraphWalker) error {
 			// then callback with the output.
 			log.Printf("[DEBUG] vertex %s.%s: evaluating", path, dag.VertexName(v))
 			tree = walker.EnterEvalTree(v, tree)
-			output, err := Eval(tree, ctx)
+			output, err := Eval(tree, vertexCtx)
 			if rerr = walker.ExitEvalTree(v, output, err); rerr != nil {
 				return
 			}
@@ -182,7 +191,7 @@ func (g *Graph) walk(walker GraphWalker) error {
 				"[DEBUG] vertex %s.%s: expanding/walking dynamic subgraph",
 				path,
 				dag.VertexName(v))
-			g, err := ev.DynamicExpand(ctx)
+			g, err := ev.DynamicExpand(vertexCtx)
 			if err != nil {
 				rerr = err
 				return

terraform/graph_config_node_module.go

@@ -227,7 +227,7 @@ func (n *graphNodeModuleExpanded) FlattenGraph() *Graph {
 		graph.Replace(v, &graphNodeModuleFlatWrap{
 			graphNodeModuleWrappable: wn,
 
-			Path:              graph.Path,
+			PathValue:         graph.Path,
 			NamePrefix:        pathStr,
 			DependentOnPrefix: depPrefix,
 		})
@@ -259,7 +259,7 @@ type graphNodeModuleWrappable interface {
 type graphNodeModuleFlatWrap struct {
 	graphNodeModuleWrappable
 
-	Path              []string
+	PathValue         []string
 	NamePrefix        string
 	DependentOnPrefix string
 }
@@ -268,6 +268,11 @@ func (n *graphNodeModuleFlatWrap) Name() string {
 	return fmt.Sprintf("%s.%s", n.NamePrefix, n.graphNodeModuleWrappable.Name())
 }
 
+// GraphNodeSubPath impl.
+func (n *graphNodeModuleFlatWrap) Path() []string {
+	return n.PathValue
+}
+
 func (n *graphNodeModuleFlatWrap) DependableName() []string {
 	result := n.graphNodeModuleWrappable.DependableName()
 	n.prefixList(result, n.NamePrefix)

terraform/graph_interface_subgraph.go

@@ -0,0 +1,7 @@
+package terraform
+
+// GraphNodeSubPath says that a node is part of a graph with a
+// different path, and the context should be adjusted accordingly.
+type GraphNodeSubPath interface {
+	Path() []string
+}

terraform/graph_walk.go

@@ -7,8 +7,8 @@ import (
 // GraphWalker is an interface that can be implemented that when used
 // with Graph.Walk will invoke the given callbacks under certain events.
 type GraphWalker interface {
-	EnterGraph(*Graph) EvalContext
-	ExitGraph(*Graph)
+	EnterPath([]string) EvalContext
+	ExitPath([]string)
 	EnterVertex(dag.Vertex)
 	ExitVertex(dag.Vertex, error)
 	EnterEvalTree(dag.Vertex, EvalNode) EvalNode
@@ -20,8 +20,8 @@ type GraphWalker interface {
 // implementing all the required functions.
 type NullGraphWalker struct{}
 
-func (NullGraphWalker) EnterGraph(*Graph) EvalContext                   { return nil }
-func (NullGraphWalker) ExitGraph(*Graph)                                {}
+func (NullGraphWalker) EnterPath([]string) EvalContext                  { return nil }
+func (NullGraphWalker) ExitPath([]string)                               {}
 func (NullGraphWalker) EnterVertex(dag.Vertex)                          {}
 func (NullGraphWalker) ExitVertex(dag.Vertex, error)                    {}
 func (NullGraphWalker) EnterEvalTree(v dag.Vertex, n EvalNode) EvalNode { return n }

terraform/graph_walk_context.go

@@ -33,14 +33,14 @@ type ContextGraphWalker struct {
 	provisionerLock     sync.Mutex
 }
 
-func (w *ContextGraphWalker) EnterGraph(g *Graph) EvalContext {
+func (w *ContextGraphWalker) EnterPath(path []string) EvalContext {
 	w.once.Do(w.init)
 
 	w.contextLock.Lock()
 	defer w.contextLock.Unlock()
 
 	// If we already have a context for this path cached, use that
-	key := PathCacheKey(g.Path)
+	key := PathCacheKey(path)
 	if ctx, ok := w.contexts[key]; ok {
 		return ctx
 	}
@@ -49,13 +49,13 @@ func (w *ContextGraphWalker) EnterGraph(g *Graph) EvalContext {
 	// to the root module. As we enter subgraphs, we don't want to set
 	// variables, which is set by the SetVariables EvalContext function.
 	variables := w.Context.variables
-	if len(g.Path) > 1 {
+	if len(path) > 1 {
 		// We're in a submodule, the variables should be empty
 		variables = make(map[string]string)
 	}
 
 	ctx := &BuiltinEvalContext{
-		PathValue:           g.Path,
+		PathValue:           path,
 		Hooks:               w.Context.hooks,
 		InputValue:          w.Context.uiInput,
 		Providers:           w.Context.providers,