feat: add local schema diff

If no remote URI is specified for schema diff it will attempt to diff the local project

closes #2174

cmd/ftl/cmd_schema_diff.go

@@ -2,9 +2,13 @@ package main
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"github.com/TBD54566975/ftl/common/projectconfig"
+	"google.golang.org/protobuf/proto"
 	"net/url"
 	"os"
+	"path/filepath"
 
 	"connectrpc.com/connect"
 	"github.com/hexops/gotextdiff"
@@ -22,12 +26,19 @@ import (
 )
 
 type schemaDiffCmd struct {
-	OtherEndpoint url.URL `arg:"" help:"Other endpoint URL to compare against."`
+	OtherEndpoint url.URL `arg:"" help:"Other endpoint URL to compare against. If this is not specified then ftl will perform a diff against the local schema." optional:""`
 	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)
+func (d *schemaDiffCmd) Run(ctx context.Context, currentURL *url.URL, projConfig projectconfig.Config) error {
+	var other *schema.Schema
+	var err error
+	if d.OtherEndpoint.String() == "" {
+		other, err = localSchema(ctx, projConfig)
+	} else {
+		other, err = schemaForURL(ctx, d.OtherEndpoint)
+	}
+
 	if err != nil {
 		return fmt.Errorf("failed to get other schema: %w", err)
 	}
@@ -57,6 +68,61 @@ func (d *schemaDiffCmd) Run(ctx context.Context, currentURL *url.URL) error {
 	return nil
 }
 
+func localSchema(ctx context.Context, moduleDirs projectconfig.Config) (*schema.Schema, error) {
+	pb := &schemapb.Schema{}
+	found := false
+	tried := ""
+	moduleFound := false
+	moduleTried := ""
+	for _, modulePaths := range moduleDirs.AbsModuleDirs() {
+		entries, err := os.ReadDir(modulePaths)
+		if err != nil {
+			return nil, fmt.Errorf("failed to list directory %w", err)
+		}
+		for _, module := range entries {
+			if !module.IsDir() {
+				continue
+			}
+			path := filepath.Join(modulePaths, module.Name(), ".ftl", "schema.pb")
+			mod, err := loadProtoSchema(path)
+			if err != nil {
+				moduleTried += fmt.Sprintf("failed to read schema file %s; did you run ftl build?", path)
+			} else {
+				println(path)
+				moduleFound = true
+				found = true
+				pb.Modules = append(pb.Modules, mod)
+			}
+		}
+	}
+	if !moduleFound {
+		tried += moduleTried
+	}
+
+	if !found {
+		return nil, errors.New(tried)
+	}
+
+	s, err := schema.FromProto(pb)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse local schema: %w", err)
+	}
+	return s, nil
+}
+
+func loadProtoSchema(file string) (*schemapb.Module, error) {
+	content, err := os.ReadFile(file)
+	if err != nil {
+		return nil, err
+	}
+	module := &schemapb.Module{}
+	err = proto.Unmarshal(content, module)
+	if err != nil {
+		return nil, err
+	}
+	return module, 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{}))