Add basic resource trimming command (#41780)

* Add basic trim command

* Indent properly

* Actually apply defaults if the user asks for it

pkg/cmd/grafana-cli/commands/commands.go

@@ -214,6 +214,22 @@ so must be recompiled to validate newly-added CUE files.`,
 			},
 		},
 	},
+	{
+		Name:   "trim-resource",
+		Usage:  "trim schema-specified defaults from a resource",
+		Action: runCueCommand(cmd.trimResource),
+		Flags: []cli.Flag{
+			&cli.StringFlag{
+				Name:  "dashboard",
+				Usage: "path to file containing (valid) dashboard JSON",
+			},
+			&cli.BoolFlag{
+				Name:  "apply",
+				Usage: "invert the operation: apply defaults instead of trimming them",
+				Value: false,
+			},
+		},
+	},
 	{
 		Name:  "gen-ts",
 		Usage: "generate TypeScript from all known CUE file types",

pkg/cmd/grafana-cli/commands/trim_command.go

@@ -0,0 +1,59 @@
+package commands
+
+import (
+	"bytes"
+	"encoding/json"
+	gerrors "errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+
+	"cuelang.org/go/cue/errors"
+	"github.com/grafana/grafana/pkg/cmd/grafana-cli/utils"
+	"github.com/grafana/grafana/pkg/schema"
+	"github.com/grafana/grafana/pkg/schema/load"
+)
+
+func (cmd Command) trimResource(c utils.CommandLine) error {
+	filename := c.String("dashboard")
+	if filename == "" {
+		return gerrors.New("must specify dashboard file path with --dashboard")
+	}
+	apply := c.Bool("apply")
+
+	f, err := os.Open(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	b, err := io.ReadAll(f)
+	if err != nil {
+		return err
+	}
+
+	res := schema.Resource{Value: string(b), Name: filename}
+	sch, err := load.DistDashboardFamily(paths)
+	if err != nil {
+		return fmt.Errorf("error while loading dashboard scuemata, err: %w", err)
+	}
+
+	var out schema.Resource
+	if apply {
+		out, err = schema.ApplyDefaults(res, sch.CUE())
+	} else {
+		out, err = schema.TrimDefaults(res, sch.CUE())
+	}
+
+	if err != nil {
+		return gerrors.New(errors.Details(err, nil))
+	}
+
+	b = []byte(out.Value.(string))
+	var buf bytes.Buffer
+	err = json.Indent(&buf, b, "", "  ")
+	if err != nil {
+		return err
+	}
+	fmt.Println(buf.String())
+	return nil
+}