Merge pull request #29235 from magodo/terraform_add_output_append

`terraform add`: `-out` option append to existing config & optionally check resource existance

internal/command/add.go

@@ -3,6 +3,7 @@ package command
 import (
 	"fmt"
 	"os"
+	"path/filepath"
 	"strings"
 
 	"github.com/hashicorp/hcl/v2"
@@ -33,6 +34,43 @@ func (c *AddCommand) Run(rawArgs []string) int {
 		return 1
 	}
 
+	// In case the output configuration path is specified, we should ensure the
+	// target resource address doesn't exist in the module tree indicated by
+	// the existing configuration files.
+	if args.OutPath != "" {
+		// Ensure the directory to the path exists and is accessible.
+		outDir := filepath.Dir(args.OutPath)
+		if _, err := os.Stat(outDir); os.IsNotExist(err) {
+			diags = diags.Append(tfdiags.Sourceless(
+				tfdiags.Error,
+				"The out path doesn't exist or is not accessible",
+				err.Error(),
+			))
+			view.Diagnostics(diags)
+			return 1
+		}
+
+		config, loadDiags := c.loadConfig(outDir)
+		diags = diags.Append(loadDiags)
+		if diags.HasErrors() {
+			view.Diagnostics(diags)
+			return 1
+		}
+
+		if config != nil && config.Module != nil {
+			if rs, ok := config.Module.ManagedResources[args.Addr.ContainingResource().Config().String()]; ok {
+				diags = diags.Append(&hcl.Diagnostic{
+					Severity: hcl.DiagError,
+					Summary:  "Resource already in configuration",
+					Detail:   fmt.Sprintf("The resource %s is already in this configuration at %s. Resource names must be unique per type in each module.", args.Addr, rs.DeclRange),
+					Subject:  &rs.DeclRange,
+				})
+				c.View.Diagnostics(diags)
+				return 1
+			}
+		}
+	}
+
 	// Check for user-supplied plugin path
 	var err error
 	if c.pluginPath, err = c.loadPluginPath(); err != nil {
@@ -127,21 +165,6 @@ func (c *AddCommand) Run(rawArgs []string) int {
 		}
 	}
 
-	if module == nil {
-		// It's fine if the module doesn't actually exist; we don't need to check if the resource exists.
-	} else {
-		if rs, ok := module.ManagedResources[args.Addr.ContainingResource().Config().String()]; ok {
-			diags = diags.Append(&hcl.Diagnostic{
-				Severity: hcl.DiagError,
-				Summary:  "Resource already in configuration",
-				Detail:   fmt.Sprintf("The resource %s is already in this configuration at %s. Resource names must be unique per type in each module.", args.Addr, rs.DeclRange),
-				Subject:  &rs.DeclRange,
-			})
-			c.View.Diagnostics(diags)
-			return 1
-		}
-	}
-
 	// Get the schemas from the context
 	schemas, moreDiags := lr.Core.Schemas(lr.Config, lr.InputState)
 	diags = diags.Append(moreDiags)

internal/command/add_test.go

@@ -118,6 +118,45 @@ resource "test_instance" "new" {
 		}
 	})
 
+	t.Run("basic to existing file", func(t *testing.T) {
+		view, done := testView(t)
+		c := &AddCommand{
+			Meta: Meta{
+				testingOverrides: overrides,
+				View:             view,
+			},
+		}
+		outPath := "add.tf"
+		args := []string{fmt.Sprintf("-out=%s", outPath), "test_instance.new"}
+		c.Run(args)
+		args = []string{fmt.Sprintf("-out=%s", outPath), "test_instance.new2"}
+		code := c.Run(args)
+		output := done(t)
+		if code != 0 {
+			fmt.Println(output.Stderr())
+			t.Fatalf("wrong exit status. Got %d, want 0", code)
+		}
+		expected := `resource "test_instance" "new" {
+  value = null # REQUIRED string
+}
+resource "test_instance" "new2" {
+  value = null # REQUIRED string
+}
+`
+		result, err := os.ReadFile(outPath)
+		if err != nil {
+			t.Fatalf("error reading result file %s: %s", outPath, err.Error())
+		}
+		// While the entire directory will get removed once the whole test suite
+		// is done, we remove this lest it gets in the way of another (not yet
+		// written) test.
+		os.Remove(outPath)
+
+		if !cmp.Equal(expected, string(result)) {
+			t.Fatalf("wrong output:\n%s", cmp.Diff(expected, string(result)))
+		}
+	})
+
 	t.Run("optionals", func(t *testing.T) {
 		view, done := testView(t)
 		c := &AddCommand{
@@ -194,7 +233,8 @@ resource "test_instance" "new" {
 				View:             view,
 			},
 		}
-		args := []string{"test_instance.exists"}
+		outPath := "add.tf"
+		args := []string{fmt.Sprintf("-out=%s", outPath), "test_instance.exists"}
 		code := c.Run(args)
 		if code != 1 {
 			t.Fatalf("wrong exit status. Got %d, want 0", code)
@@ -206,6 +246,31 @@ resource "test_instance" "new" {
 		}
 	})
 
+	t.Run("output existing resource to stdout", func(t *testing.T) {
+		view, done := testView(t)
+		c := &AddCommand{
+			Meta: Meta{
+				testingOverrides: overrides,
+				View:             view,
+			},
+		}
+		args := []string{"test_instance.exists"}
+		code := c.Run(args)
+		output := done(t)
+		if code != 0 {
+			fmt.Println(output.Stderr())
+			t.Fatalf("wrong exit status. Got %d, want 0", code)
+		}
+		expected := `resource "test_instance" "exists" {
+  value = null # REQUIRED string
+}
+`
+
+		if !cmp.Equal(output.Stdout(), expected) {
+			t.Fatalf("wrong output:\n%s", cmp.Diff(expected, output.Stdout()))
+		}
+	})
+
 	t.Run("provider not in configuration", func(t *testing.T) {
 		view, done := testView(t)
 		c := &AddCommand{

internal/command/views/add.go

@@ -84,7 +84,14 @@ func (v *addHuman) Resource(addr addrs.AbsResourceInstance, schema *configschema
 	} else {
 		// The Println call above adds this final newline automatically; we add it manually here.
 		formatted = append(formatted, '\n')
-		return os.WriteFile(v.outPath, formatted, 0600)
+
+		f, err := os.OpenFile(v.outPath, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0600)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		_, err = f.Write(formatted)
+		return err
 	}
 }