feat: ftl schema diff (#2043)

Fixes #1989

```
ftl schema diff --help
Usage: ftl schema diff <other-endpoint> [flags]

Print any schema differences between this cluster and another cluster. Returns
an exit code of 1 if there are differences.

Arguments:
  <other-endpoint>    Other endpoint URL to compare against.

  --endpoint=http://127.0.0.1:8892     FTL endpoint to bind/connect to ($FTL_ENDPOINT).
  --color    Enable colored output regardless of TTY.
```

- Compares `<other-endpoint>` vs `--endpoint` into a unified diff with
color.
- Exits with 1 if there is a difference.
- Detects tty and will not emit ANSI unless `--color` is passed in.

<img width="1104" alt="image"
src="https://github.com/TBD54566975/ftl/assets/31338/7aa704ae-9df0-48c7-90d5-56f97f4d556c">

cmd/ftl/cmd_schema.go

@@ -2,6 +2,7 @@ package main
 
 type schemaCmd struct {
 	Get      getSchemaCmd      `default:"" cmd:"" help:"Retrieve the cluster FTL schema."`
+	Diff     schemaDiffCmd     `cmd:"" help:"Print any schema differences between this cluster and another cluster. Returns an exit code of 1 if there are differences."`
 	Protobuf schemaProtobufCmd `cmd:"" help:"Generate protobuf schema mirroring the FTL schema structure."`
 	Generate schemaGenerateCmd `cmd:"" help:"Stream the schema from the cluster and generate files from the template."`
 	Import   schemaImportCmd   `cmd:"" help:"Import messages to the FTL schema."`

cmd/ftl/cmd_schema_diff.go

@@ -0,0 +1,85 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"net/url"
+	"os"
+
+	"connectrpc.com/connect"
+	"github.com/hexops/gotextdiff"
+	"github.com/hexops/gotextdiff/myers"
+	"github.com/hexops/gotextdiff/span"
+	"github.com/mattn/go-isatty"
+
+	ftlv1 "github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1"
+	"github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/ftlv1connect"
+	schemapb "github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/schema"
+	"github.com/TBD54566975/ftl/backend/schema"
+	"github.com/TBD54566975/ftl/internal/log"
+	"github.com/TBD54566975/ftl/internal/rpc"
+	"github.com/alecthomas/chroma/v2/quick"
+)
+
+type schemaDiffCmd struct {
+	OtherEndpoint url.URL `arg:"" help:"Other endpoint URL to compare against."`
+	Color         bool    `help:"Enable colored output regardless of TTY."`
+}
+
+func (d *schemaDiffCmd) Run(ctx context.Context, currentURL *url.URL) error {
+	other, err := schemaForURL(ctx, d.OtherEndpoint)
+	if err != nil {
+		return fmt.Errorf("failed to get other schema: %w", err)
+	}
+	current, err := schemaForURL(ctx, *currentURL)
+	if err != nil {
+		return fmt.Errorf("failed to get current schema: %w", err)
+	}
+
+	edits := myers.ComputeEdits(span.URIFromPath(""), other.String(), current.String())
+	diff := fmt.Sprint(gotextdiff.ToUnified(d.OtherEndpoint.String(), currentURL.String(), other.String(), edits))
+
+	color := d.Color || isatty.IsTerminal(os.Stdout.Fd())
+	if color {
+		err = quick.Highlight(os.Stdout, diff, "diff", "terminal256", "solarized-dark")
+		if err != nil {
+			return fmt.Errorf("failed to highlight diff: %w", err)
+		}
+	} else {
+		fmt.Print(diff)
+	}
+
+	// Similar to the `diff` command, exit with 1 if there are differences.
+	if diff != "" {
+		os.Exit(1)
+	}
+
+	return nil
+}
+
+func schemaForURL(ctx context.Context, url url.URL) (*schema.Schema, error) {
+	client := rpc.Dial(ftlv1connect.NewControllerServiceClient, url.String(), log.Error)
+	resp, err := client.PullSchema(ctx, connect.NewRequest(&ftlv1.PullSchemaRequest{}))
+	if err != nil {
+		return nil, fmt.Errorf("url %s: failed to pull schema: %w", url.String(), err)
+	}
+
+	pb := &schemapb.Schema{}
+	for resp.Receive() {
+		msg := resp.Msg()
+		pb.Modules = append(pb.Modules, msg.Schema)
+		if !msg.More {
+			break
+		}
+	}
+	if resp.Err() != nil {
+		return nil, fmt.Errorf("url %s: failed to receive schema: %w", url.String(), resp.Err())
+	}
+
+	s, err := schema.FromProto(pb)
+	if err != nil {
+		return nil, fmt.Errorf("url %s: failed to parse schema: %w", url.String(), err)
+	}
+
+	return s, nil
+}

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/TBD54566975/scaffolder v1.0.0
 	github.com/alecthomas/assert/v2 v2.10.0
 	github.com/alecthomas/atomic v0.1.0-alpha2
+	github.com/alecthomas/chroma/v2 v2.14.0
 	github.com/alecthomas/concurrency v0.0.2
 	github.com/alecthomas/kong v0.9.0
 	github.com/alecthomas/kong-toml v0.2.0
@@ -121,7 +122,7 @@ require (
 	github.com/godbus/dbus/v5 v5.1.0 // indirect
 	github.com/google/pprof v0.0.0-20240409012703-83162a5b38cd // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.20.0 // indirect
-	github.com/hexops/gotextdiff v1.0.3 // indirect
+	github.com/hexops/gotextdiff v1.0.3
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a // indirect
 	github.com/jackc/puddle/v2 v2.2.1 // indirect