feat(migrations): Add option migration for inputs.disk

config/migration.go

@@ -151,7 +151,7 @@ func ApplyMigrations(data []byte) ([]byte, uint64, error) {
 		return nil, 0, fmt.Errorf("assigning text failed: %w", err)
 	}
 
-	// Do the actual migration(s)
+	// Do the actual plugin migration(s)
 	var applied uint64
 	for idx, s := range sections {
 		migrate, found := migrations.PluginMigrations[s.name]
@@ -168,10 +168,39 @@ func ApplyMigrations(data []byte) ([]byte, uint64, error) {
 			log.Printf("I! Plugin %q in line %d: %s", s.name, s.begin, msg)
 		}
 		s.raw = bytes.NewBuffer(result)
+		tbl, err := toml.Parse(s.raw.Bytes())
+		if err != nil {
+			return nil, 0, fmt.Errorf("reparsing migrated %q (line %d) failed: %w", s.name, s.begin, err)
+		}
+		s.content = tbl
+		sections[idx] = s
+		applied++
+	}
+
+	// Do the actual plugin option migration(s)
+	for idx, s := range sections {
+		migrate, found := migrations.PluginOptionMigrations[s.name]
+		if !found {
+			continue
+		}
+
+		log.Printf("D!   migrating options of plugin %q in line %d...", s.name, s.begin)
+		result, msg, err := migrate(s.content)
+		if err != nil {
+			if errors.Is(err, migrations.ErrNotApplicable) {
+				continue
+			}
+			return nil, 0, fmt.Errorf("migrating options of %q (line %d) failed: %w", s.name, s.begin, err)
+		}
+		if msg != "" {
+			log.Printf("I! Plugin %q in line %d: %s", s.name, s.begin, msg)
+		}
+		s.raw = bytes.NewBuffer(result)
 		sections[idx] = s
 		applied++
 	}
 
+	// Reconstruct the config file from the sections
 	var buf bytes.Buffer
 	for _, s := range sections {
 		_, err = s.raw.WriteTo(&buf)

migrations/all/inputs_disk.go

@@ -0,0 +1,5 @@
+//go:build !custom || (migrations && (inputs || inputs.disk))
+
+package all
+
+import _ "github.com/influxdata/telegraf/migrations/inputs_disk" // register migration

migrations/inputs_disk/migration.go

@@ -0,0 +1,83 @@
+package inputs_disk
+
+import (
+	"fmt"
+
+	"github.com/influxdata/toml"
+	"github.com/influxdata/toml/ast"
+
+	"github.com/influxdata/telegraf/internal/choice"
+	"github.com/influxdata/telegraf/migrations"
+)
+
+// Migration function
+func migrate(tbl *ast.Table) ([]byte, string, error) {
+	// Decode the old data structure
+	var plugin map[string]interface{}
+	if err := toml.UnmarshalTable(tbl, &plugin); err != nil {
+		return nil, "", err
+	}
+
+	// Check for deprecated option(s) and migrate them
+	var applied bool
+	if rawDeprecatedMountpoints, found := plugin["mountpoints"]; found {
+		applied = true
+
+		// Convert the options to the actual type
+		deprecatedMountpoints, ok := rawDeprecatedMountpoints.([]interface{})
+		if !ok {
+			err := fmt.Errorf("unexpected type for deprecated 'mountpoints' option: %T", rawDeprecatedMountpoints)
+			return nil, "", err
+		}
+
+		// Merge the option with the replacement
+		var mountpoints []string
+		if rawMountpoints, found := plugin["mount_points"]; found {
+			mountpointsList, ok := rawMountpoints.([]interface{})
+			if !ok {
+				err := fmt.Errorf("unexpected type for 'mount_points' option: %T", rawMountpoints)
+				return nil, "", err
+			}
+			for _, raw := range mountpointsList {
+				mp, ok := raw.(string)
+				if !ok {
+					err := fmt.Errorf("unexpected type for 'mount_points' option: %T", raw)
+					return nil, "", err
+				}
+				mountpoints = append(mountpoints, mp)
+			}
+		}
+		for _, raw := range deprecatedMountpoints {
+			dmp, ok := raw.(string)
+			if !ok {
+				err := fmt.Errorf("unexpected type for deprecated 'mountpoints' option: %T", raw)
+				return nil, "", err
+			}
+
+			if !choice.Contains(dmp, mountpoints) {
+				mountpoints = append(mountpoints, dmp)
+			}
+		}
+
+		// Remove the deprecated option and replace the modified one
+		delete(plugin, "mountpoints")
+		plugin["mount_points"] = mountpoints
+	}
+
+	// No options migrated so we can exit early
+	if !applied {
+		return nil, "", migrations.ErrNotApplicable
+	}
+
+	// Create the corresponding plugin configurations
+	cfg := migrations.CreateTOMLStruct("inputs", "disk")
+	cfg.Add("inputs", "disk", plugin)
+
+	output, err := toml.Marshal(cfg)
+	return output, "", err
+}
+
+// Register the migration function for the plugin type
+func init() {
+	migrations.AddPluginOptionMigration("inputs.disk", migrate)
+}

migrations/inputs_disk/migration_test.go

@@ -0,0 +1,86 @@
+package inputs_disk_test
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/influxdata/telegraf/config"
+	_ "github.com/influxdata/telegraf/migrations/inputs_disk" // register migration
+	_ "github.com/influxdata/telegraf/plugins/inputs/disk"    // register plugin
+)
+
+func TestNoMigration(t *testing.T) {
+	defaultCfg := []byte(`
+# Read metrics about disk usage by mount point
+[[inputs.disk]]
+  ## By default stats will be gathered for all mount points.
+  ## Set mount_points will restrict the stats to only the specified mount points.
+  # mount_points = ["/"]
+
+  ## Ignore mount points by filesystem type.
+  ignore_fs = ["tmpfs", "devtmpfs", "devfs", "iso9660", "overlay", "aufs", "squashfs"]
+
+  ## Ignore mount points by mount options.
+  ## The 'mount' command reports options of all mounts in parathesis.
+  ## Bind mounts can be ignored with the special 'bind' option.
+  # ignore_mount_opts = []
+`)
+
+	// Migrate and check that nothing changed
+	output, n, err := config.ApplyMigrations(defaultCfg)
+	require.NoError(t, err)
+	require.NotEmpty(t, output)
+	require.Zero(t, n)
+	require.Equal(t, string(defaultCfg), string(output))
+}
+
+func TestCases(t *testing.T) {
+	// Get all directories in testdata
+	folders, err := os.ReadDir("testcases")
+	require.NoError(t, err)
+
+	for _, f := range folders {
+		// Only handle folders
+		if !f.IsDir() {
+			continue
+		}
+
+		t.Run(f.Name(), func(t *testing.T) {
+			testcasePath := filepath.Join("testcases", f.Name())
+			inputFile := filepath.Join(testcasePath, "telegraf.conf")
+			expectedFile := filepath.Join(testcasePath, "expected.conf")
+
+			// Read the expected output
+			expected := config.NewConfig()
+			require.NoError(t, expected.LoadConfig(expectedFile))
+			require.NotEmpty(t, expected.Inputs)
+
+			// Read the input data
+			input, remote, err := config.LoadConfigFile(inputFile)
+			require.NoError(t, err)
+			require.False(t, remote)
+			require.NotEmpty(t, input)
+
+			// Migrate
+			output, n, err := config.ApplyMigrations(input)
+			require.NoError(t, err)
+			require.NotEmpty(t, output)
+			require.GreaterOrEqual(t, n, uint64(1))
+			actual := config.NewConfig()
+			require.NoError(t, actual.LoadConfigData(output))
+
+			// Test the output
+			require.Len(t, actual.Inputs, len(expected.Inputs))
+			actualIDs := make([]string, 0, len(expected.Inputs))
+			expectedIDs := make([]string, 0, len(expected.Inputs))
+			for i := range actual.Inputs {
+				actualIDs = append(actualIDs, actual.Inputs[i].ID())
+				expectedIDs = append(expectedIDs, expected.Inputs[i].ID())
+			}
+			require.ElementsMatch(t, expectedIDs, actualIDs, string(output))
+		})
+	}
+}

migrations/inputs_disk/testcases/deprecated_mountpoints/expected.conf

@@ -0,0 +1,3 @@
+[[inputs.disk]]
+mount_points = ["/mnt/disk", "/srv", "/mnt/others"]
+ignore_fs = ["tmpfs", "devtmpfs", "devfs", "iso9660", "overlay", "aufs", "squashfs"]

migrations/inputs_disk/testcases/deprecated_mountpoints/telegraf.conf

@@ -0,0 +1,7 @@
+# Read metrics about disk usage by mount point
+[[inputs.disk]]
+  ## Deprecated mountpoint option
+  mountpoints = ["/mnt/disk", "/srv", "/mnt/others"]
+
+  ## Ignore mount points by filesystem type.
+  ignore_fs = ["tmpfs", "devtmpfs", "devfs", "iso9660", "overlay", "aufs", "squashfs"]

migrations/inputs_disk/testcases/deprecated_mountpoints_existing/expected.conf

@@ -0,0 +1,3 @@
+[[inputs.disk]]
+mount_points = ["/", "/srv", "/mnt/disk", "/mnt/others"]
+ignore_fs = ["tmpfs", "devtmpfs", "devfs", "iso9660", "overlay", "aufs", "squashfs"]

migrations/inputs_disk/testcases/deprecated_mountpoints_existing/telegraf.conf

@@ -0,0 +1,11 @@
+# Read metrics about disk usage by mount point
+[[inputs.disk]]
+  ## Deprecated mountpoint option
+  mountpoints = ["/mnt/disk", "/srv", "/mnt/others"]
+
+  ## By default stats will be gathered for all mount points.
+  ## Set mount_points will restrict the stats to only the specified mount points.
+  mount_points = ["/", "/srv"]
+
+  ## Ignore mount points by filesystem type.
+  ignore_fs = ["tmpfs", "devtmpfs", "devfs", "iso9660", "overlay", "aufs", "squashfs"]

migrations/registry.go

@@ -1,11 +1,14 @@
 package migrations
 
 import (
+	"errors"
 	"fmt"
 
 	"github.com/influxdata/toml/ast"
 )
 
+var ErrNotApplicable = errors.New("no migration applied")
+
 type PluginMigrationFunc func(*ast.Table) ([]byte, string, error)
 
 var PluginMigrations = make(map[string]PluginMigrationFunc)
@@ -17,6 +20,17 @@ func AddPluginMigration(name string, f PluginMigrationFunc) {
 	PluginMigrations[name] = f
 }
 
+type PluginOptionMigrationFunc PluginMigrationFunc
+
+var PluginOptionMigrations = make(map[string]PluginOptionMigrationFunc)
+
+func AddPluginOptionMigration(name string, f PluginOptionMigrationFunc) {
+	if _, found := PluginOptionMigrations[name]; found {
+		panic(fmt.Errorf("plugin option migration function already registered for %q", name))
+	}
+	PluginOptionMigrations[name] = f
+}
+
 type pluginTOMLStruct map[string]map[string][]interface{}
 
 func CreateTOMLStruct(category, name string) pluginTOMLStruct {