refactor providers command argument parsing

internal/command/arguments/providers.go

@@ -0,0 +1,42 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: BUSL-1.1
+
+package arguments
+
+import "github.com/hashicorp/terraform/internal/tfdiags"
+
+// Providers represents the command-line arguments for the providers command.
+type Providers struct {
+	// TestsDirectory is the directory containing Terraform test files.
+	TestsDirectory string
+}
+
+// ParseProviders processes CLI arguments, returning a Providers value and
+// errors. If errors are encountered, a Providers value is still returned
+// representing the best effort interpretation of the arguments.
+func ParseProviders(args []string) (*Providers, tfdiags.Diagnostics) {
+	var diags tfdiags.Diagnostics
+	providers := &Providers{}
+
+	cmdFlags := defaultFlagSet("providers")
+	cmdFlags.StringVar(&providers.TestsDirectory, "test-directory", "tests", "test-directory")
+
+	if err := cmdFlags.Parse(args); err != nil {
+		diags = diags.Append(tfdiags.Sourceless(
+			tfdiags.Error,
+			"Failed to parse command-line flags",
+			err.Error(),
+		))
+	}
+
+	args = cmdFlags.Args()
+	if len(args) > 0 {
+		diags = diags.Append(tfdiags.Sourceless(
+			tfdiags.Error,
+			"Too many command line arguments",
+			"Did you mean to use -chdir?",
+		))
+	}
+
+	return providers, diags
+}

internal/command/arguments/providers_test.go

@@ -0,0 +1,88 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: BUSL-1.1
+
+package arguments
+
+import (
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/hashicorp/terraform/internal/tfdiags"
+)
+
+func TestParseProviders_valid(t *testing.T) {
+	testCases := map[string]struct {
+		args []string
+		want *Providers
+	}{
+		"defaults": {
+			nil,
+			&Providers{
+				TestsDirectory: "tests",
+			},
+		},
+		"test directory": {
+			[]string{"-test-directory=integration-tests"},
+			&Providers{
+				TestsDirectory: "integration-tests",
+			},
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			got, diags := ParseProviders(tc.args)
+			if len(diags) > 0 {
+				t.Fatalf("unexpected diags: %v", diags)
+			}
+			if diff := cmp.Diff(tc.want, got); diff != "" {
+				t.Fatalf("unexpected result\n%s", diff)
+			}
+		})
+	}
+}
+
+func TestParseProviders_invalid(t *testing.T) {
+	testCases := map[string]struct {
+		args      []string
+		want      *Providers
+		wantDiags tfdiags.Diagnostics
+	}{
+		"unknown flag": {
+			[]string{"-wat"},
+			&Providers{
+				TestsDirectory: "tests",
+			},
+			tfdiags.Diagnostics{
+				tfdiags.Sourceless(
+					tfdiags.Error,
+					"Failed to parse command-line flags",
+					"flag provided but not defined: -wat",
+				),
+			},
+		},
+		"too many positional arguments": {
+			[]string{"foo"},
+			&Providers{
+				TestsDirectory: "tests",
+			},
+			tfdiags.Diagnostics{
+				tfdiags.Sourceless(
+					tfdiags.Error,
+					"Too many command line arguments",
+					"Did you mean to use -chdir?",
+				),
+			},
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			got, gotDiags := ParseProviders(tc.args)
+			if diff := cmp.Diff(tc.want, got); diff != "" {
+				t.Fatalf("unexpected result\n%s", diff)
+			}
+			tfdiags.AssertDiagnosticsMatch(t, gotDiags, tc.wantDiags)
+		})
+	}
+}

internal/command/providers.go

@@ -31,26 +31,19 @@ func (c *ProvidersCommand) Synopsis() string {
 }
 
 func (c *ProvidersCommand) Run(args []string) int {
-	var testsDirectory string
-
-	args = c.Meta.process(args)
-	cmdFlags := c.Meta.defaultFlagSet("providers")
-	cmdFlags.StringVar(&testsDirectory, "test-directory", "tests", "test-directory")
-	cmdFlags.Usage = func() { c.Ui.Error(c.Help()) }
-	if err := cmdFlags.Parse(args); err != nil {
-		c.Ui.Error(fmt.Sprintf("Error parsing command-line flags: %s\n", err.Error()))
+	parsedArgs, diags := arguments.ParseProviders(c.Meta.process(args))
+	if diags.HasErrors() {
+		c.showDiagnostics(diags)
 		return 1
 	}
 
-	configPath, err := ModulePath(cmdFlags.Args())
+	configPath, err := ModulePath(nil)
 	if err != nil {
 		c.Ui.Error(err.Error())
 		return 1
 	}
 
-	var diags tfdiags.Diagnostics
-
-	empty, err := configs.IsEmptyDir(configPath, testsDirectory)
+	empty, err := configs.IsEmptyDir(configPath, parsedArgs.TestsDirectory)
 	if err != nil {
 		diags = diags.Append(tfdiags.Sourceless(
 			tfdiags.Error,
@@ -74,7 +67,7 @@ func (c *ProvidersCommand) Run(args []string) int {
 		return 1
 	}
 
-	config, configDiags := c.loadConfigWithTests(configPath, testsDirectory)
+	config, configDiags := c.loadConfigWithTests(configPath, parsedArgs.TestsDirectory)
 	diags = diags.Append(configDiags)
 	if configDiags.HasErrors() {
 		c.showDiagnostics(diags)