implement GraphNodeModulePath

GraphNodeModulePath is similar to GraphNodeSubPath, except that it
returns an addrs.Module rather than an addrs.ModuleInstance. This is
used by the ReferenceTransformer to connect references, when modules may
not yet be expanded.

Because references only exist within the scope of a module, we can
connect everything knowing only the module path. If the reference is to
an expanded module instance output, we can still properly order the
reference because we'll wait for the entire module to complete
evaluation.

terraform/graph_interface_subgraph.go

@@ -9,3 +9,9 @@ import (
 type GraphNodeSubPath interface {
 	Path() addrs.ModuleInstance
 }
+
+// GraphNodeModulePath is implemented by all referenceable nodes, to indicate
+// their configuration path in unexpanded modules.
+type GraphNodeModulePath interface {
+	ModulePath() addrs.Module
+}

terraform/node_local.go

@@ -34,6 +34,11 @@ func (n *NodeLocal) Path() addrs.ModuleInstance {
 	return n.Addr.Module
 }
 
+// GraphNodeModulePath
+func (n *NodeLocal) ModulePath() addrs.Module {
+	return n.Addr.Module.Module()
+}
+
 // RemovableIfNotTargeted
 func (n *NodeLocal) RemoveIfNotTargeted() bool {
 	return true

terraform/node_module_expand.go

@@ -39,6 +39,14 @@ func (n *nodeExpandModule) Path() addrs.ModuleInstance {
 	return n.CallerAddr
 }
 
+// GraphNodeModulePath implementation
+func (n *nodeExpandModule) ModulePath() addrs.Module {
+	// This node represents the module call within a module,
+	// so return the CallerAddr as the path as the module
+	// call may expand into multiple child instances
+	return n.Addr
+}
+
 // GraphNodeReferencer implementation
 func (n *nodeExpandModule) References() []*addrs.Reference {
 	var refs []*addrs.Reference

terraform/node_module_removed.go

@@ -29,6 +29,14 @@ func (n *NodeModuleRemoved) Path() addrs.ModuleInstance {
 	return n.Addr
 }
 
+// GraphNodeModulePath implementation
+func (n *NodeModuleRemoved) ModulePath() addrs.Module {
+	// This node represents the module call within a module,
+	// so return the CallerAddr as the path as the module
+	// call may expand into multiple child instances
+	return n.Addr.Module()
+}
+
 // GraphNodeEvalable
 func (n *NodeModuleRemoved) EvalTree() EvalNode {
 	return &EvalOpFilter{

terraform/node_module_variable.go

@@ -54,6 +54,11 @@ func (n *NodePlannableModuleVariable) Path() addrs.ModuleInstance {
 	return n.Module.UnkeyedInstanceShim()
 }
 
+// GraphNodeModulePath
+func (n *NodePlannableModuleVariable) ModulePath() addrs.Module {
+	return n.Module
+}
+
 // GraphNodeReferencer
 func (n *NodePlannableModuleVariable) References() []*addrs.Reference {
 
@@ -137,6 +142,11 @@ func (n *NodeApplyableModuleVariable) Path() addrs.ModuleInstance {
 	return n.Addr.Module.Parent()
 }
 
+// GraphNodeModulePath
+func (n *NodeApplyableModuleVariable) ModulePath() addrs.Module {
+	return n.Addr.Module.Parent().Module()
+}
+
 // RemovableIfNotTargeted
 func (n *NodeApplyableModuleVariable) RemoveIfNotTargeted() bool {
 	// We need to add this so that this node will be removed if

terraform/node_output.go

@@ -51,6 +51,11 @@ func (n *NodePlannableOutput) Path() addrs.ModuleInstance {
 	return n.Module.UnkeyedInstanceShim()
 }
 
+// GraphNodeModulePath
+func (n *NodePlannableOutput) ModulePath() addrs.Module {
+	return n.Module
+}
+
 // GraphNodeReferenceable
 func (n *NodePlannableOutput) ReferenceableAddrs() []addrs.Referenceable {
 	// An output in the root module can't be referenced at all.
@@ -128,6 +133,11 @@ func (n *NodeApplyableOutput) Path() addrs.ModuleInstance {
 	return n.Addr.Module
 }
 
+// GraphNodeModulePath
+func (n *NodeApplyableOutput) ModulePath() addrs.Module {
+	return n.Addr.Module.Module()
+}
+
 // RemovableIfNotTargeted
 func (n *NodeApplyableOutput) RemoveIfNotTargeted() bool {
 	// We need to add this so that this node will be removed if
@@ -254,6 +264,11 @@ func (n *NodeDestroyableOutput) Path() addrs.ModuleInstance {
 	return n.Module.UnkeyedInstanceShim()
 }
 
+// GraphNodeModulePath
+func (n *NodeDestroyableOutput) ModulePath() addrs.Module {
+	return n.Module
+}
+
 // RemovableIfNotTargeted
 func (n *NodeDestroyableOutput) RemoveIfNotTargeted() bool {
 	// We need to add this so that this node will be removed if

terraform/node_output_orphan.go

@@ -37,6 +37,11 @@ func (n *NodeOutputOrphan) Path() addrs.ModuleInstance {
 	return n.Addr.Module
 }
 
+// GraphNodeModulePath
+func (n *NodeOutputOrphan) ModulePath() addrs.Module {
+	return n.Addr.Module.Module()
+}
+
 // GraphNodeEvalable
 func (n *NodeOutputOrphan) EvalTree() EvalNode {
 	return &EvalOpFilter{

terraform/node_provider_abstract.go

@@ -44,6 +44,11 @@ func (n *NodeAbstractProvider) Path() addrs.ModuleInstance {
 	return n.Addr.Module
 }
 
+// GraphNodeModulePath
+func (n *NodeAbstractProvider) ModulePath() addrs.Module {
+	return n.Addr.Module.Module()
+}
+
 // RemovableIfNotTargeted
 func (n *NodeAbstractProvider) RemoveIfNotTargeted() bool {
 	// We need to add this so that this node will be removed if

terraform/node_resource_abstract.go

@@ -153,6 +153,11 @@ func (n *NodeAbstractResource) Path() addrs.ModuleInstance {
 	return n.Addr.Module
 }
 
+// GraphNodeModulePath
+func (n *NodeAbstractResource) ModulePath() addrs.Module {
+	return n.Addr.Module.Module()
+}
+
 // GraphNodeReferenceable
 func (n *NodeAbstractResource) ReferenceableAddrs() []addrs.Referenceable {
 	return []addrs.Referenceable{n.Addr.Resource}

terraform/node_root_variable.go

@@ -27,6 +27,10 @@ func (n *NodeRootVariable) Path() addrs.ModuleInstance {
 	return addrs.RootModuleInstance
 }
 
+func (n *NodeRootVariable) ModulePath() addrs.Module {
+	return addrs.RootModule
+}
+
 // GraphNodeReferenceable
 func (n *NodeRootVariable) ReferenceableAddrs() []addrs.Referenceable {
 	return []addrs.Referenceable{n.Addr}

terraform/transform_reference.go

@@ -22,7 +22,7 @@ import (
 // be referenced and other methods of referencing may still be possible (such
 // as by path!)
 type GraphNodeReferenceable interface {
-	GraphNodeSubPath
+	GraphNodeModulePath
 
 	// ReferenceableAddrs returns a list of addresses through which this can be
 	// referenced.
@@ -32,7 +32,7 @@ type GraphNodeReferenceable interface {
 // GraphNodeReferencer must be implemented by nodes that reference other
 // Terraform items and therefore depend on them.
 type GraphNodeReferencer interface {
-	GraphNodeSubPath
+	GraphNodeModulePath
 
 	// References returns a list of references made by this node, which
 	// include both a referenced address and source location information for
@@ -252,9 +252,6 @@ func (m *ReferenceMap) References(v dag.Vertex) []dag.Vertex {
 	if !ok {
 		return nil
 	}
-	if _, ok := v.(GraphNodeSubPath); !ok {
-		return nil
-	}
 
 	var matches []dag.Vertex
 
@@ -298,11 +295,11 @@ func (m *ReferenceMap) mapKey(path addrs.ModuleInstance, addr addrs.Referenceabl
 //
 // Only GraphNodeSubPath implementations can be referenced, so this method will
 // panic if the given vertex does not implement that interface.
-func (m *ReferenceMap) vertexReferenceablePath(v dag.Vertex) addrs.ModuleInstance {
-	sp, ok := v.(GraphNodeSubPath)
+func vertexReferenceablePath(v dag.Vertex) addrs.ModuleInstance {
+	sp, ok := v.(GraphNodeModulePath)
 	if !ok {
 		// Only nodes with paths can participate in a reference map.
-		panic(fmt.Errorf("vertexMapKey on vertex type %T which doesn't implement GraphNodeSubPath", sp))
+		panic(fmt.Errorf("vertexMapKey on vertex type %T which doesn't implement GraphNodeModulePath", sp))
 	}
 
 	if outside, ok := v.(GraphNodeReferenceOutside); ok {
@@ -313,7 +310,7 @@ func (m *ReferenceMap) vertexReferenceablePath(v dag.Vertex) addrs.ModuleInstanc
 	}
 
 	// Vertex is referenced from the same module as where it was declared.
-	return sp.Path()
+	return sp.ModulePath().UnkeyedInstanceShim()
 }
 
 // vertexReferencePath returns the path in which references _from_ the given
@@ -321,14 +318,14 @@ func (m *ReferenceMap) vertexReferenceablePath(v dag.Vertex) addrs.ModuleInstanc
 //
 // Only GraphNodeSubPath implementations can have references, so this method
 // will panic if the given vertex does not implement that interface.
-func vertexReferencePath(referrer dag.Vertex) addrs.ModuleInstance {
-	sp, ok := referrer.(GraphNodeSubPath)
+func vertexReferencePath(v dag.Vertex) addrs.ModuleInstance {
+	sp, ok := v.(GraphNodeModulePath)
 	if !ok {
 		// Only nodes with paths can participate in a reference map.
-		panic(fmt.Errorf("vertexReferencePath on vertex type %T which doesn't implement GraphNodeSubPath", sp))
+		panic(fmt.Errorf("vertexReferencePath on vertex type %T which doesn't implement GraphNodeModulePath", v))
 	}
 
-	if outside, ok := referrer.(GraphNodeReferenceOutside); ok {
+	if outside, ok := v.(GraphNodeReferenceOutside); ok {
 		// Vertex makes references to objects in a different module than where
 		// it was declared.
 		_, path := outside.ReferenceOutside()
@@ -337,7 +334,7 @@ func vertexReferencePath(referrer dag.Vertex) addrs.ModuleInstance {
 
 	// Vertex makes references to objects in the same module as where it
 	// was declared.
-	return sp.Path()
+	return sp.ModulePath().UnkeyedInstanceShim()
 }
 
 // referenceMapKey produces keys for the "edges" map. "referrer" is the vertex
@@ -374,7 +371,7 @@ func NewReferenceMap(vs []dag.Vertex) *ReferenceMap {
 			continue
 		}
 
-		path := m.vertexReferenceablePath(v)
+		path := vertexReferenceablePath(v)
 
 		// Go through and cache them
 		for _, addr := range rn.ReferenceableAddrs() {

terraform/transform_reference_test.go

@@ -153,6 +153,10 @@ func (n *graphNodeRefParentTest) Path() addrs.ModuleInstance {
 	return normalizeModulePath(n.PathValue)
 }
 
+func (n *graphNodeRefParentTest) ModulePath() addrs.Module {
+	return normalizeModulePath(n.PathValue).Module()
+}
+
 type graphNodeRefChildTest struct {
 	NameValue string
 	PathValue []string
@@ -179,6 +183,10 @@ func (n *graphNodeRefChildTest) Path() addrs.ModuleInstance {
 	return normalizeModulePath(n.PathValue)
 }
 
+func (n *graphNodeRefChildTest) ModulePath() addrs.Module {
+	return normalizeModulePath(n.PathValue).Module()
+}
+
 const testTransformRefBasicStr = `
 A
 B