feat: Supports watch param (#25)

* rename overwriteOutput param to replaceOutput

* watch

* watch readme

* adjust doc

* simplify outConfig with convert errors

* join err check

* waitForFileEvent

Author: lantoli

README.md

@@ -32,7 +32,9 @@ you can also use shorter aliases, e.g.:
 atlas tf clu2adv -f in.tf -o out.tf
 ```
 
-If you want to overwrite the output file if it exists, or even use the same output file as the input file, use the `--overwriteOutput true` or the `-w` flag.
+If you want to overwrite the output file if it exists, or even use the same output file as the input file, use the `--replaceOutput true` or the `-r` flag.
+
+You can use the `--watch true` or the `-w` flag to keep the plugin running and watching for changes in the input file. You can have input and output files open in an editor and see easily how changes to the input file affect the output file.
 
 ### Limitations
 

go.mod

@@ -3,6 +3,7 @@ module github.com/mongodb-labs/atlas-cli-plugin-terraform
 go 1.23.6
 
 require (
+	github.com/fsnotify/fsnotify v1.8.0
 	github.com/hashicorp/hcl/v2 v2.23.0
 	github.com/sebdah/goldie/v2 v2.5.5
 	github.com/spf13/afero v1.12.0
@@ -23,6 +24,7 @@ require (
 	github.com/spf13/pflag v1.0.5 // indirect
 	golang.org/x/mod v0.22.0 // indirect
 	golang.org/x/sync v0.10.0 // indirect
+	golang.org/x/sys v0.29.0 // indirect
 	golang.org/x/text v0.21.0 // indirect
 	golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect

go.sum

@@ -6,6 +6,8 @@ github.com/cpuguy83/go-md2man/v2 v2.0.4/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46t
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/fsnotify/fsnotify v1.8.0 h1:dAwr6QBTBZIkG8roQaJjGof0pp0EeF+tNV7YBP3F/8M=
+github.com/fsnotify/fsnotify v1.8.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
 github.com/go-test/deep v1.0.3 h1:ZrJSEWsXzPOxaZnFteGEfooLba+ju3FYIbOrS+rQd68=
 github.com/go-test/deep v1.0.3/go.mod h1:wGDj63lr65AM2AQyKZd/NYHGb0R+1RLqB8NKt3aSFNA=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
@@ -49,6 +51,8 @@ golang.org/x/mod v0.22.0 h1:D4nJWe9zXqHOmWqj4VMOJhvzj7bEZg4wEYa759z1pH4=
 golang.org/x/mod v0.22.0/go.mod h1:6SkKJ3Xj0I0BrPOZoBy3bdMptDDU9oJrpohJ3eWZ1fY=
 golang.org/x/sync v0.10.0 h1:3NQrjDixjgGwUOCaF8w2+VYHv0Ve/vGYSbdkTa98gmQ=
 golang.org/x/sync v0.10.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/sys v0.29.0 h1:TPYlXGxvx1MGTn2GiZDhnjPA9wZzZeGKHHmKhHYvgaU=
+golang.org/x/sys v0.29.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/text v0.21.0 h1:zyQAAkrwaneQ066sspRyJaG9VNi/YJ1NfzcGB3hZ/qo=
 golang.org/x/text v0.21.0/go.mod h1:4IBbMaMmOPCJ8SecivzSH54+73PCFmPWxNTLm+vZkEQ=
 golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d h1:vU5i/LfpvrRCpgM/VPfJLg5KjxD3E+hfT1SH+d9zLwg=

internal/cli/clu2adv/clu2adv.go

@@ -23,6 +23,7 @@ func Builder() *cobra.Command {
 	_ = cmd.MarkFlagRequired("file")
 	cmd.Flags().StringVarP(&o.output, "output", "o", "", "output file")
 	_ = cmd.MarkFlagRequired("output")
-	cmd.Flags().BoolVarP(&o.overwriteOutput, "overwriteOutput", "w", false, "overwrite output file if exists")
+	cmd.Flags().BoolVarP(&o.replaceOutput, "replaceOutput", "r", false, "replace output file if exists")
+	cmd.Flags().BoolVarP(&o.watch, "watch", "w", false, "keeps the plugin running and watches the input file for changes")
 	return cmd
 }

internal/cli/clu2adv/opts.go

@@ -1,41 +1,96 @@
 package clu2adv
 
 import (
+	"errors"
 	"fmt"
 
+	"github.com/fsnotify/fsnotify"
 	"github.com/mongodb-labs/atlas-cli-plugin-terraform/internal/convert"
 	"github.com/mongodb-labs/atlas-cli-plugin-terraform/internal/file"
 	"github.com/spf13/afero"
 )
 
 type opts struct {
-	fs              afero.Fs
-	file            string
-	output          string
-	overwriteOutput bool
+	fs            afero.Fs
+	file          string
+	output        string
+	replaceOutput bool
+	watch         bool
 }
 
 func (o *opts) PreRun() error {
 	if err := file.MustExist(o.fs, o.file); err != nil {
 		return err
 	}
-	if !o.overwriteOutput {
+	if !o.replaceOutput {
 		return file.MustNotExist(o.fs, o.output)
 	}
 	return nil
 }
 
 func (o *opts) Run() error {
+	if err := o.generateFile(false); err != nil {
+		return err
+	}
+	if o.watch {
+		return o.watchFile()
+	}
+	return nil
+}
+
+func (o *opts) generateFile(allowParseErrors bool) error {
 	inConfig, err := afero.ReadFile(o.fs, o.file)
 	if err != nil {
 		return fmt.Errorf("failed to read file %s: %w", o.file, err)
 	}
 	outConfig, err := convert.ClusterToAdvancedCluster(inConfig)
 	if err != nil {
-		return err
+		if allowParseErrors {
+			outConfig = []byte("# CONVERT ERROR: " + err.Error() + "\n\n")
+			outConfig = append(outConfig, inConfig...)
+		} else {
+			return err
+		}
 	}
 	if err := afero.WriteFile(o.fs, o.output, outConfig, 0o600); err != nil {
 		return fmt.Errorf("failed to write file %s: %w", o.output, err)
 	}
 	return nil
 }
+
+func (o *opts) watchFile() error {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		return nil
+	}
+	defer watcher.Close()
+	if err := watcher.Add(o.file); err != nil {
+		return err
+	}
+	for {
+		if err := o.waitForFileEvent(watcher); err != nil {
+			return err
+		}
+	}
+}
+
+func (o *opts) waitForFileEvent(watcher *fsnotify.Watcher) error {
+	watcherError := errors.New("watcher has been closed")
+	select {
+	case event, ok := <-watcher.Events:
+		if !ok {
+			return watcherError
+		}
+		if event.Has(fsnotify.Write) {
+			if err := o.generateFile(true); err != nil {
+				return err
+			}
+		}
+	case err, ok := <-watcher.Errors:
+		if !ok {
+			return watcherError
+		}
+		return err
+	}
+	return nil
+}