command: Add vars to modules command

internal/command/arguments/modules.go

@@ -9,6 +9,9 @@ import "github.com/hashicorp/terraform/internal/tfdiags"
 type Modules struct {
 	// ViewType specifies which output format to use: human, JSON, or "raw"
 	ViewType ViewType
+
+	// Vars are the variable-related flags (-var, -var-file).
+	Vars *Vars
 }
 
 // ParseModules processes CLI arguments, returning a Modules value and error
@@ -18,8 +21,10 @@ func ParseModules(args []string) (*Modules, tfdiags.Diagnostics) {
 	var diags tfdiags.Diagnostics
 	var jsonOutput bool
 
-	modules := &Modules{}
-	cmdFlags := defaultFlagSet("modules")
+	modules := &Modules{
+		Vars: &Vars{},
+	}
+	cmdFlags := extendedFlagSet("modules", nil, nil, modules.Vars)
 	cmdFlags.BoolVar(&jsonOutput, "json", false, "json")
 
 	if err := cmdFlags.Parse(args); err != nil {

internal/command/arguments/modules_test.go

@@ -6,6 +6,8 @@ package arguments
 import (
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
 	"github.com/hashicorp/terraform/internal/tfdiags"
 )
 
@@ -18,24 +20,28 @@ func TestParseModules_valid(t *testing.T) {
 			nil,
 			&Modules{
 				ViewType: ViewHuman,
+				Vars:     &Vars{},
 			},
 		},
 		"json": {
 			[]string{"-json"},
 			&Modules{
 				ViewType: ViewJSON,
+				Vars:     &Vars{},
 			},
 		},
 	}
 
+	cmpOpts := cmpopts.IgnoreUnexported(Vars{})
+
 	for name, tc := range testCases {
 		t.Run(name, func(t *testing.T) {
 			got, diags := ParseModules(tc.args)
 			if len(diags) > 0 {
 				t.Fatalf("unexpected diags: %v", diags)
 			}
-			if *got != *tc.want {
-				t.Fatalf("unexpected result\n got: %#v\nwant: %#v", got, tc.want)
+			if diff := cmp.Diff(tc.want, got, cmpOpts); diff != "" {
+				t.Fatalf("unexpected result\n%s", diff)
 			}
 		})
 	}
@@ -51,6 +57,7 @@ func TestParseModules_invalid(t *testing.T) {
 			[]string{"-sauron"},
 			&Modules{
 				ViewType: ViewHuman,
+				Vars:     &Vars{},
 			},
 			tfdiags.Diagnostics{
 				tfdiags.Sourceless(
@@ -64,6 +71,7 @@ func TestParseModules_invalid(t *testing.T) {
 			[]string{"-json", "frodo"},
 			&Modules{
 				ViewType: ViewJSON,
+				Vars:     &Vars{},
 			},
 			tfdiags.Diagnostics{
 				tfdiags.Sourceless(
@@ -75,13 +83,59 @@ func TestParseModules_invalid(t *testing.T) {
 		},
 	}
 
+	cmpOpts := cmpopts.IgnoreUnexported(Vars{})
+
 	for name, tc := range testCases {
 		t.Run(name, func(t *testing.T) {
 			got, gotDiags := ParseModules(tc.args)
-			if *got != *tc.want {
-				t.Fatalf("unexpected result\n got: %#v\nwant: %#v", got, tc.want)
+			if diff := cmp.Diff(tc.want, got, cmpOpts); diff != "" {
+				t.Fatalf("unexpected result\n%s", diff)
 			}
 			tfdiags.AssertDiagnosticsMatch(t, gotDiags, tc.wantDiags)
 		})
 	}
 }
+
+func TestParseModules_vars(t *testing.T) {
+	testCases := map[string]struct {
+		args []string
+		want []FlagNameValue
+	}{
+		"var": {
+			args: []string{"-var", "foo=bar"},
+			want: []FlagNameValue{
+				{Name: "-var", Value: "foo=bar"},
+			},
+		},
+		"var-file": {
+			args: []string{"-var-file", "cool.tfvars"},
+			want: []FlagNameValue{
+				{Name: "-var-file", Value: "cool.tfvars"},
+			},
+		},
+		"both": {
+			args: []string{
+				"-var", "foo=bar",
+				"-var-file", "cool.tfvars",
+				"-var", "boop=beep",
+			},
+			want: []FlagNameValue{
+				{Name: "-var", Value: "foo=bar"},
+				{Name: "-var-file", Value: "cool.tfvars"},
+				{Name: "-var", Value: "boop=beep"},
+			},
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			got, diags := ParseModules(tc.args)
+			if len(diags) > 0 {
+				t.Fatalf("unexpected diags: %v", diags)
+			}
+			if vars := got.Vars.All(); !cmp.Equal(vars, tc.want) {
+				t.Fatalf("unexpected vars: %#v", vars)
+			}
+		})
+	}
+}

internal/command/modules.go

@@ -48,6 +48,23 @@ func (c *ModulesCommand) Run(rawArgs []string) int {
 	// Set up the command's view
 	view := views.NewModules(c.viewType, c.View)
 
+	loader, err := c.initConfigLoader()
+	if err != nil {
+		diags = diags.Append(err)
+		view.Diagnostics(diags)
+		return 1
+	}
+
+	var varDiags tfdiags.Diagnostics
+	c.VariableValues, varDiags = args.Vars.CollectValues(func(filename string, src []byte) {
+		loader.Parser().ForceFileSource(filename, src)
+	})
+	diags = diags.Append(varDiags)
+	if diags.HasErrors() {
+		view.Diagnostics(diags)
+		return 1
+	}
+
 	rootModPath, err := ModulePath([]string{})
 	if err != nil {
 		diags = diags.Append(err)
@@ -127,6 +144,15 @@ Usage: terraform [global options] modules [options]
 
 Options:
 
-  -json            If specified, output declared Terraform modules and
-                   their resolved versions in a machine-readable format.
+  -json               If specified, output declared Terraform modules and
+                      their resolved versions in a machine-readable format.
+
+  -var 'foo=bar'      Set a value for one of the input variables in the root
+                      module of the configuration. Use this option more than
+                      once to set more than one variable.
+
+  -var-file=filename  Load variable values from the given file, in addition
+                      to the default files terraform.tfvars and *.auto.tfvars.
+                      Use this option more than once to include more than one
+                      variables file.
 `