fix: require a project toml for ftl dev and ftl serve

cmd/ftl/cmd_dev.go

@@ -34,6 +34,9 @@ func (d *devCmd) Run(ctx context.Context, projConfig projectconfig.Config) error
 	if len(d.Dirs) == 0 && len(d.External) == 0 {
 		return errors.New("no directories specified")
 	}
+	if len(projConfig.FilePaths()) == 0 {
+		return errors.New("configuration file not found, create an ftl-project.toml file or specify one with -C")
+	}
 
 	client := rpc.ClientFromContext[ftlv1connect.ControllerServiceClient](ctx)
 
@@ -45,7 +48,7 @@ func (d *devCmd) Run(ctx context.Context, projConfig projectconfig.Config) error
 	}
 	if !d.NoServe {
 		if d.ServeCmd.Stop {
-			err := d.ServeCmd.Run(ctx)
+			err := d.ServeCmd.Run(ctx, projConfig)
 			if err != nil {
 				return err
 			}
@@ -55,7 +58,7 @@ func (d *devCmd) Run(ctx context.Context, projConfig projectconfig.Config) error
 			return errors.New(ftlRunningErrorMsg)
 		}
 
-		g.Go(func() error { return d.ServeCmd.Run(ctx) })
+		g.Go(func() error { return d.ServeCmd.Run(ctx, projConfig) })
 	}
 
 	g.Go(func() error {

cmd/ftl/cmd_serve.go

@@ -22,6 +22,7 @@ import (
 	"github.com/TBD54566975/ftl/backend/controller/sql/databasetesting"
 	ftlv1 "github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1"
 	"github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/ftlv1connect"
+	"github.com/TBD54566975/ftl/common/projectconfig"
 	"github.com/TBD54566975/ftl/internal/bind"
 	"github.com/TBD54566975/ftl/internal/container"
 	"github.com/TBD54566975/ftl/internal/log"
@@ -44,7 +45,11 @@ type serveCmd struct {
 const ftlContainerName = "ftl-db-1"
 const ftlRunningErrorMsg = "FTL is already running. Use 'ftl serve --stop' to stop it"
 
-func (s *serveCmd) Run(ctx context.Context) error {
+func (s *serveCmd) Run(ctx context.Context, projConfig projectconfig.Config) error {
+	if len(projConfig.FilePaths()) == 0 {
+		return errors.New("configuration file not found, create an ftl-project.toml file or specify one with -C")
+	}
+
 	logger := log.FromContext(ctx)
 	client := rpc.ClientFromContext[ftlv1connect.ControllerServiceClient](ctx)
 

common/projectconfig/merge.go

@@ -8,7 +8,7 @@ import (
 //
 // Config is merged left to right, with later files taking precedence over earlier files.
 func Merge(paths ...string) (Config, error) {
-	config := Config{}
+	config := Config{filePaths: paths}
 	for _, path := range paths {
 		partial, err := loadFile(path)
 		if err != nil {

common/projectconfig/projectconfig.go

@@ -33,13 +33,17 @@ type Config struct {
 	Commands      Commands                    `toml:"commands"`
 	FTLMinVersion string                      `toml:"ftl-min-version"`
 	absModuleDirs []string
+	filePaths     []string
 }
 
 // AbsModuleDirsOrDefault returns the absolute path for the module-dirs field from the ftl-project.toml, unless
 // that is not defined, in which case it defaults to the root directory.
 func (c Config) AbsModuleDirsOrDefault() []string { return c.absModuleDirs }
 
-// ConfigPaths returns the computed list of configuration paths to load.
+// FilePaths returns the list of configuration files that generated this Config.
+func (c Config) FilePaths() []string { return c.filePaths }
+
+// ConfigPaths returns the computed list of configuration paths to load, or an empty list if none are found.
 func ConfigPaths(input []string) []string {
 	if len(input) > 0 {
 		return input
@@ -80,7 +84,7 @@ func CreateDefaultFileIfNonexistent(ctx context.Context) error {
 		return err
 	}
 	logger.Debugf("Creating a new project config file at %q", path)
-	return Save(path, Config{})
+	return Save(path, Config{filePaths: []string{path}})
 }
 
 func LoadConfig(ctx context.Context, input []string) (Config, error) {
@@ -108,7 +112,7 @@ func LoadWritableConfig(ctx context.Context, input []string) (Config, error) {
 	logger := log.FromContext(ctx)
 	if _, err := os.Stat(target); errors.Is(err, os.ErrNotExist) {
 		logger.Debugf("Creating a new project config file at %q", target)
-		err = Save(target, Config{})
+		err = Save(target, Config{filePaths: []string{target}})
 		if err != nil {
 			return Config{}, err
 		}
@@ -120,7 +124,7 @@ func LoadWritableConfig(ctx context.Context, input []string) (Config, error) {
 
 // Load project config from a file.
 func loadFile(path string) (Config, error) {
-	config := Config{}
+	config := Config{filePaths: []string{path}}
 	md, err := toml.DecodeFile(path, &config)
 	if err != nil {
 		return Config{}, err

common/projectconfig/projectconfig_test.go

@@ -30,6 +30,7 @@ func TestProjectConfig(t *testing.T) {
 		Commands: Commands{
 			Startup: []string{"echo 'Executing global pre-build command'"},
 		},
+		filePaths: []string{"testdata/ftl-project.toml"},
 	}
 
 	assert.Equal(t, expected, actual)
@@ -41,18 +42,33 @@ func TestProjectLoadConfig(t *testing.T) {
 		paths []string
 		err   string
 	}{
-		{name: "AllValid", paths: []string{"testdata/ftl-project.toml"}},
+		{name: "SingleValid", paths: []string{"testdata/ftl-project.toml"}},
+		{name: "MultipleValid", paths: []string{"testdata/ftl-project.toml", "testdata/go/configs-ftl-project.toml"}},
 		{name: "IsNonExistent", paths: []string{"testdata/ftl-project-nonexistent.toml"}, err: "no such file or directory"},
 		{name: "ContainsNonExistent", paths: []string{"testdata/ftl-project.toml", "testdata/ftl-project-nonexistent.toml"}, err: "no such file or directory"},
 	}
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			_, err := LoadConfig(log.ContextWithNewDefaultLogger(context.Background()), test.paths)
+			config, err := LoadConfig(log.ContextWithNewDefaultLogger(context.Background()), test.paths)
 			if test.err != "" {
+				assert.Error(t, err)
 				assert.Contains(t, err.Error(), test.err)
 			} else {
 				assert.NoError(t, err)
+
+				// Check that all test.paths exist in config.FilePaths
+				assert.Equal(t, len(test.paths), len(config.FilePaths()))
+				for _, path := range test.paths {
+					found := false
+					for _, configPath := range config.FilePaths() {
+						if path == configPath {
+							found = true
+							break
+						}
+					}
+					assert.True(t, found, "expected path %q not found in config.FilePaths", path)
+				}
 			}
 		})
 	}