revert: "fix: add a build.lock file to gate the buildengine (#1670)" (#…

…1732)

This reverts commit e711523.

```
=== Failed
=== FAIL: buildengine TestDissallowMultipleEngines (0.00s)
    /home/runner/work/ftl/ftl/buildengine/engine_test.go:65: Did not expect an error but got:
        failed to lock file at: /home/runner/.ftl/build.lock

DONE 383 tests, 1 skipped, 1 failure in 115.533s
Error: === RUN   TestDissallowMultipleEngines
    buildengine/engine_test.go:65: Did not expect an error but got:
        failed to lock file at: /home/runner/.ftl/build.lock
```

cc @safeer

buildengine/engine.go

@@ -6,15 +6,13 @@ import (
 	"crypto/sha256"
 	"errors"
 	"fmt"
-	"os"
 	"path/filepath"
 	"runtime"
 	"strings"
 	"time"
 
 	"connectrpc.com/connect"
 	"github.com/alecthomas/types/pubsub"
-	"github.com/gofrs/flock"
 	"github.com/jpillora/backoff"
 	"github.com/puzpuzpuz/xsync/v3"
 	"golang.org/x/exp/maps"
@@ -85,13 +83,6 @@ func WithListener(listener Listener) Option {
 //
 // "dirs" are directories to scan for local modules.
 func New(ctx context.Context, client ftlv1connect.ControllerServiceClient, moduleDirs []string, externalDirs []string, options ...Option) (*Engine, error) {
-	logger := log.FromContext(ctx)
-	lock, err := acquireBuildLock()
-	if err != nil {
-		return nil, err
-	}
-	logger.Debugf("Acquired lock file at %s", lock.Path())
-
 	ctx = rpc.ContextWithClient(ctx, client)
 	e := &Engine{
 		client:           client,
@@ -111,14 +102,6 @@ func New(ctx context.Context, client ftlv1connect.ControllerServiceClient, modul
 	ctx, cancel := context.WithCancel(ctx)
 	e.cancel = cancel
 
-	go func() {
-		<-ctx.Done()
-		err := lock.Unlock()
-		if err != nil {
-			logger.Errorf(err, "failed to unlock file at %s", lock.Path())
-		}
-	}()
-
 	projects, err := DiscoverProjects(ctx, moduleDirs, externalDirs)
 	if err != nil {
 		return nil, fmt.Errorf("could not find projects: %w", err)
@@ -184,26 +167,6 @@ func (e *Engine) Close() error {
 	return nil
 }
 
-func acquireBuildLock() (*flock.Flock, error) {
-	homeDir, err := os.UserHomeDir()
-	if err != nil {
-		return nil, err
-	}
-	lockFile := filepath.Join(homeDir, ".ftl", "build.lock")
-	if err := os.MkdirAll(filepath.Dir(lockFile), 0750); err != nil {
-		return nil, err
-	}
-	lock := flock.New(lockFile)
-	locked, err := lock.TryLock()
-	if err != nil {
-		return nil, err
-	}
-	if !locked {
-		return nil, fmt.Errorf("failed to lock file at: %s", lockFile)
-	}
-	return lock, nil
-}
-
 // Graph returns the dependency graph for the given modules.
 //
 // If no modules are provided, the entire graph is returned. An error is returned if

buildengine/engine_test.go

@@ -58,13 +58,3 @@ func TestEngine(t *testing.T) {
 	err = engine.Build(ctx)
 	assert.NoError(t, err)
 }
-
-func TestDissallowMultipleEngines(t *testing.T) {
-	ctx := log.ContextWithNewDefaultLogger(context.Background())
-	engine, err := buildengine.New(ctx, nil, []string{"testdata/projects/alpha"}, nil)
-	assert.NoError(t, err)
-	defer engine.Close()
-
-	_, err = buildengine.New(ctx, nil, []string{"testdata/projects/alpha"}, nil)
-	assert.Error(t, err)
-}