core: ResourceAddress.MatchesConfig method

This is a useful building block for filtering configuration based on a
resource address. It is similar in principle to state filtering, but for
specific resource configuration blocks.

terraform/resource_address.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 
 	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/config/module"
 )
 
 // ResourceAddress is a way of identifying an individual resource (or,
@@ -108,6 +109,32 @@ func (r *ResourceAddress) WholeModuleAddress() *ResourceAddress {
 	}
 }
 
+// MatchesConfig returns true if the receiver matches the given
+// configuration resource within the given configuration module.
+//
+// Since resource configuration blocks represent all of the instances of
+// a multi-instance resource, the index of the address (if any) is not
+// considered.
+func (r *ResourceAddress) MatchesConfig(mod *module.Tree, rc *config.Resource) bool {
+	if r.HasResourceSpec() {
+		if r.Mode != rc.Mode || r.Type != rc.Type || r.Name != rc.Name {
+			return false
+		}
+	}
+
+	addrPath := r.Path
+	cfgPath := mod.Path()
+
+	// normalize
+	if len(addrPath) == 0 {
+		addrPath = nil
+	}
+	if len(cfgPath) == 0 {
+		cfgPath = nil
+	}
+	return reflect.DeepEqual(addrPath, cfgPath)
+}
+
 // stateId returns the ID that this resource should be entered with
 // in the state. This is also used for diffs. In the future, we'd like to
 // move away from this string field so I don't export this.

terraform/resource_address_test.go

@@ -1,10 +1,12 @@
 package terraform
 
 import (
+	"fmt"
 	"reflect"
 	"testing"
 
 	"github.com/hashicorp/terraform/config"
+	"github.com/hashicorp/terraform/config/module"
 )
 
 func TestParseResourceAddressInternal(t *testing.T) {
@@ -743,3 +745,179 @@ func TestResourceAddressWholeModuleAddress(t *testing.T) {
 		})
 	}
 }
+
+func TestResourceAddressMatchesConfig(t *testing.T) {
+	root := testModule(t, "empty-with-child-module")
+	child := root.Child([]string{"child"})
+	grandchild := root.Child([]string{"child", "grandchild"})
+
+	tests := []struct {
+		Addr     *ResourceAddress
+		Module   *module.Tree
+		Resource *config.Resource
+		Want     bool
+	}{
+		{
+			&ResourceAddress{
+				Mode:  config.ManagedResourceMode,
+				Type:  "null_resource",
+				Name:  "baz",
+				Index: -1,
+			},
+			root,
+			&config.Resource{
+				Mode: config.ManagedResourceMode,
+				Type: "null_resource",
+				Name: "baz",
+			},
+			true,
+		},
+		{
+			&ResourceAddress{
+				Path:  []string{"child"},
+				Mode:  config.ManagedResourceMode,
+				Type:  "null_resource",
+				Name:  "baz",
+				Index: -1,
+			},
+			child,
+			&config.Resource{
+				Mode: config.ManagedResourceMode,
+				Type: "null_resource",
+				Name: "baz",
+			},
+			true,
+		},
+		{
+			&ResourceAddress{
+				Path:  []string{"child", "grandchild"},
+				Mode:  config.ManagedResourceMode,
+				Type:  "null_resource",
+				Name:  "baz",
+				Index: -1,
+			},
+			grandchild,
+			&config.Resource{
+				Mode: config.ManagedResourceMode,
+				Type: "null_resource",
+				Name: "baz",
+			},
+			true,
+		},
+		{
+			&ResourceAddress{
+				Path:  []string{"child"},
+				Index: -1,
+			},
+			child,
+			&config.Resource{
+				Mode: config.ManagedResourceMode,
+				Type: "null_resource",
+				Name: "baz",
+			},
+			true,
+		},
+		{
+			&ResourceAddress{
+				Path:  []string{"child", "grandchild"},
+				Index: -1,
+			},
+			grandchild,
+			&config.Resource{
+				Mode: config.ManagedResourceMode,
+				Type: "null_resource",
+				Name: "baz",
+			},
+			true,
+		},
+		{
+			&ResourceAddress{
+				Mode:  config.DataResourceMode,
+				Type:  "null_resource",
+				Name:  "baz",
+				Index: -1,
+			},
+			module.NewEmptyTree(),
+			&config.Resource{
+				Mode: config.ManagedResourceMode,
+				Type: "null_resource",
+				Name: "baz",
+			},
+			false,
+		},
+		{
+			&ResourceAddress{
+				Mode:  config.ManagedResourceMode,
+				Type:  "null_resource",
+				Name:  "baz",
+				Index: -1,
+			},
+			module.NewEmptyTree(),
+			&config.Resource{
+				Mode: config.ManagedResourceMode,
+				Type: "null_resource",
+				Name: "pizza",
+			},
+			false,
+		},
+		{
+			&ResourceAddress{
+				Mode:  config.ManagedResourceMode,
+				Type:  "null_resource",
+				Name:  "baz",
+				Index: -1,
+			},
+			module.NewEmptyTree(),
+			&config.Resource{
+				Mode: config.ManagedResourceMode,
+				Type: "aws_instance",
+				Name: "baz",
+			},
+			false,
+		},
+		{
+			&ResourceAddress{
+				Path:  []string{"child", "grandchild"},
+				Mode:  config.ManagedResourceMode,
+				Type:  "null_resource",
+				Name:  "baz",
+				Index: -1,
+			},
+			child,
+			&config.Resource{
+				Mode: config.ManagedResourceMode,
+				Type: "null_resource",
+				Name: "baz",
+			},
+			false,
+		},
+		{
+			&ResourceAddress{
+				Path:  []string{"child"},
+				Mode:  config.ManagedResourceMode,
+				Type:  "null_resource",
+				Name:  "baz",
+				Index: -1,
+			},
+			grandchild,
+			&config.Resource{
+				Mode: config.ManagedResourceMode,
+				Type: "null_resource",
+				Name: "baz",
+			},
+			false,
+		},
+	}
+
+	for i, test := range tests {
+		t.Run(fmt.Sprintf("%02d-%s", i, test.Addr), func(t *testing.T) {
+			got := test.Addr.MatchesConfig(test.Module, test.Resource)
+			if got != test.Want {
+				t.Errorf(
+					"wrong result\naddr: %s\nmod:  %#v\nrsrc: %#v\ngot:  %#v\nwant: %#v",
+					test.Addr, test.Module.Path(), test.Resource, got, test.Want,
+				)
+			}
+		})
+	}
+}

terraform/test-fixtures/empty-with-child-module/child/child.tf

@@ -0,0 +1,3 @@
+module "grandchild" {
+  source = "../grandchild"
+}

terraform/test-fixtures/empty-with-child-module/grandchild/grandchild.tf

@@ -0,0 +1 @@
+# Nothing here!

terraform/test-fixtures/empty-with-child-module/root.tf

@@ -0,0 +1,3 @@
+module "child" {
+  source = "./child"
+}