Support reading module outputs in terraform console (#24808)

* Include eval in output walk

This allows outputs to be evaluated in the evalwalk,
impacting terraform console. Outputs are still not evaluated
for terraform console in the root module, so this has
no impact on writing to state (as child module outputs are not
written to state). Also adds test coverage to the console command,
including for evaluating locals (another use of the evalwalk)

command/console_test.go

@@ -3,10 +3,12 @@ package command
 import (
 	"bytes"
 	"io/ioutil"
+	"os"
 	"path/filepath"
 	"strings"
 	"testing"
 
+	"github.com/hashicorp/terraform/helper/copy"
 	"github.com/mitchellh/cli"
 )
 
@@ -133,3 +135,46 @@ func TestConsole_unsetRequiredVars(t *testing.T) {
 		t.Fatalf("wrong output\ngot:\n%s\n\nwant string containing %q", got, want)
 	}
 }
+
+func TestConsole_modules(t *testing.T) {
+	td := tempDir(t)
+	copy.CopyDir(testFixturePath("modules"), td)
+	defer os.RemoveAll(td)
+	defer testChdir(t, td)()
+
+	p := testProvider()
+	ui := new(cli.MockUi)
+
+	c := &ConsoleCommand{
+		Meta: Meta{
+			testingOverrides: metaOverridesForProvider(p),
+			Ui:               ui,
+		},
+	}
+
+	commands := map[string]string{
+		"module.child.myoutput\n":          "bar\n",
+		"module.count_child[0].myoutput\n": "bar\n",
+		"local.foo\n":                      "3\n",
+	}
+
+	args := []string{
+		testFixturePath("modules"),
+	}
+
+	for cmd, val := range commands {
+		var output bytes.Buffer
+		defer testStdinPipe(t, strings.NewReader(cmd))()
+		outCloser := testStdoutCapture(t, &output)
+		code := c.Run(args)
+		outCloser()
+		if code != 0 {
+			t.Fatalf("bad: %d\n\n%s", code, ui.ErrorWriter.String())
+		}
+
+		actual := output.String()
+		if output.String() != val {
+			t.Fatalf("bad: %q, expected %q", actual, val)
+		}
+	}
+}

command/testdata/modules/.terraform/modules/modules.json

@@ -0,0 +1 @@
+{"Modules":[{"Key":"","Source":"","Dir":"."},{"Key":"child","Source":"./child","Dir":"child"},{"Key":"count_child","Source":"./child","Dir":"child"}]}

command/testdata/modules/child/main.tf

@@ -0,0 +1,5 @@
+resource "test_instance" "test" {
+}
+output "myoutput" {
+  value = "bar"
+}

command/testdata/modules/main.tf

@@ -0,0 +1,11 @@
+locals {
+  foo = 3
+}
+
+module "child" {
+  source = "./child"
+}
+module "count_child" {
+  count = 1
+  source = "./child"
+}

command/testdata/modules/terraform.tfstate

@@ -0,0 +1,23 @@
+{
+    "version": 4,
+    "terraform_version": "0.13.0",
+    "serial": 7,
+    "lineage": "9cb740e3-d64d-e53e-a8e4-99b9bcacf24b",
+    "outputs": {},
+    "resources": [
+      {
+        "module": "module.child",
+        "mode": "managed",
+        "type": "test_instance",
+        "name": "test",
+        "provider": "provider[\"registry.terraform.io/hashicorp/test\"]",
+        "instances": [
+          {
+            "schema_version": 0,
+            "attributes": {}
+          }
+        ]
+      }
+    ]
+  }
+  

terraform/node_output.go

@@ -222,7 +222,7 @@ func (n *NodeApplyableOutput) EvalTree() EvalNode {
 	return &EvalSequence{
 		Nodes: []EvalNode{
 			&EvalOpFilter{
-				Ops: []walkOperation{walkRefresh, walkPlan, walkApply, walkValidate, walkDestroy, walkPlanDestroy},
+				Ops: []walkOperation{walkEval, walkRefresh, walkPlan, walkApply, walkValidate, walkDestroy, walkPlanDestroy},
 				Node: &EvalWriteOutput{
 					Addr:      n.Addr.OutputValue,
 					Sensitive: n.Config.Sensitive,