refactor providers schema command argument parsing

internal/command/arguments/providers_schema.go

@@ -0,0 +1,50 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: BUSL-1.1
+
+package arguments
+
+import "github.com/hashicorp/terraform/internal/tfdiags"
+
+// ProvidersSchema represents the command-line arguments for the providers
+// schema command.
+type ProvidersSchema struct {
+	JSON bool
+}
+
+// ParseProvidersSchema processes CLI arguments, returning a ProvidersSchema
+// value and errors. If errors are encountered, a ProvidersSchema value is
+// still returned representing the best effort interpretation of the arguments.
+func ParseProvidersSchema(args []string) (*ProvidersSchema, tfdiags.Diagnostics) {
+	var diags tfdiags.Diagnostics
+	providersSchema := &ProvidersSchema{}
+
+	cmdFlags := defaultFlagSet("providers schema")
+	cmdFlags.BoolVar(&providersSchema.JSON, "json", false, "produce JSON output")
+
+	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",
+			"Expected no positional arguments.",
+		))
+	}
+
+	if !providersSchema.JSON {
+		diags = diags.Append(tfdiags.Sourceless(
+			tfdiags.Error,
+			"The -json flag is required",
+			"The `terraform providers schema` command requires the `-json` flag.",
+		))
+	}
+
+	return providersSchema, diags
+}

internal/command/arguments/providers_schema_test.go

@@ -0,0 +1,100 @@
+// 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 TestParseProvidersSchema_valid(t *testing.T) {
+	testCases := map[string]struct {
+		args []string
+		want *ProvidersSchema
+	}{
+		"json": {
+			[]string{"-json"},
+			&ProvidersSchema{
+				JSON: true,
+			},
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			got, diags := ParseProvidersSchema(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 TestParseProvidersSchema_invalid(t *testing.T) {
+	testCases := map[string]struct {
+		args      []string
+		want      *ProvidersSchema
+		wantDiags tfdiags.Diagnostics
+	}{
+		"missing json": {
+			nil,
+			&ProvidersSchema{
+				JSON: false,
+			},
+			tfdiags.Diagnostics{
+				tfdiags.Sourceless(
+					tfdiags.Error,
+					"The -json flag is required",
+					"The `terraform providers schema` command requires the `-json` flag.",
+				),
+			},
+		},
+		"too many positional arguments": {
+			[]string{"-json", "extra"},
+			&ProvidersSchema{
+				JSON: true,
+			},
+			tfdiags.Diagnostics{
+				tfdiags.Sourceless(
+					tfdiags.Error,
+					"Too many command line arguments",
+					"Expected no positional arguments.",
+				),
+			},
+		},
+		"unknown flag and missing json": {
+			[]string{"-wat"},
+			&ProvidersSchema{
+				JSON: false,
+			},
+			tfdiags.Diagnostics{
+				tfdiags.Sourceless(
+					tfdiags.Error,
+					"Failed to parse command-line flags",
+					"flag provided but not defined: -wat",
+				),
+				tfdiags.Sourceless(
+					tfdiags.Error,
+					"The -json flag is required",
+					"The `terraform providers schema` command requires the `-json` flag.",
+				),
+			},
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			got, gotDiags := ParseProvidersSchema(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_schema.go

@@ -10,7 +10,6 @@ import (
 	"github.com/hashicorp/terraform/internal/backend/backendrun"
 	"github.com/hashicorp/terraform/internal/command/arguments"
 	"github.com/hashicorp/terraform/internal/command/jsonprovider"
-	"github.com/hashicorp/terraform/internal/tfdiags"
 )
 
 // ProvidersCommand is a Command implementation that prints out information
@@ -28,23 +27,12 @@ func (c *ProvidersSchemaCommand) Synopsis() string {
 }
 
 func (c *ProvidersSchemaCommand) Run(args []string) int {
-	args = c.Meta.process(args)
-	cmdFlags := c.Meta.defaultFlagSet("providers schema")
-	var jsonOutput bool
-	cmdFlags.BoolVar(&jsonOutput, "json", false, "produce JSON output")
-
-	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()))
+	_, diags := arguments.ParseProvidersSchema(c.Meta.process(args))
+	if diags.HasErrors() {
+		c.showDiagnostics(diags)
 		return 1
 	}
 
-	if !jsonOutput {
-		c.Ui.Error(
-			"The `terraform providers schema` command requires the `-json` flag.\n")
-		cmdFlags.Usage()
-		return 1
-	}
 	viewType := arguments.ViewJSON // See above; enforced use of JSON output
 
 	// Check for user-supplied plugin path
@@ -53,9 +41,6 @@ func (c *ProvidersSchemaCommand) Run(args []string) int {
 		c.Ui.Error(fmt.Sprintf("Error loading plugin path: %s", err))
 		return 1
 	}
-
-	var diags tfdiags.Diagnostics
-
 	// Load the backend
 	b, backendDiags := c.backend(".", viewType)
 	diags = diags.Append(backendDiags)