feat: pass kotlin build errors to the language server

fixes #1123
fixes #1159

backend/schema/errors.go

@@ -3,6 +3,8 @@ package schema
 import (
 	"errors"
 	"fmt"
+
+	schemapb "github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/schema"
 )
 
 type Error struct {
@@ -12,8 +14,32 @@ type Error struct {
 	Err       error    `protobuf:"-"` // Wrapped error, if any
 }
 
+func errorFromProto(e *schemapb.Error) *Error {
+	return &Error{
+		Pos:       posFromProto(e.Pos),
+		Msg:       e.Msg,
+		EndColumn: int(e.EndColumn),
+	}
+}
+
+func errorsFromProto(errs []*schemapb.Error) []*Error {
+	var out []*Error
+	for _, pb := range errs {
+		s := errorFromProto(pb)
+		out = append(out, s)
+	}
+	return out
+}
+
 type ErrorList struct {
-	Errors []Error `json:"errors" protobuf:"1"`
+	Errors []*Error `json:"errors" protobuf:"1"`
+}
+
+// ErrorListFromProto converts a protobuf ErrorList to an ErrorList.
+func ErrorListFromProto(e *schemapb.ErrorList) *ErrorList {
+	return &ErrorList{
+		Errors: errorsFromProto(e.Errors),
+	}
 }
 
 func (e Error) Error() string { return fmt.Sprintf("%s-%d: %s", e.Pos, e.EndColumn, e.Msg) }

buildengine/build_go_test.go

@@ -125,7 +125,7 @@ func Nothing(context.Context) error {
 		buildDir:  "_ftl",
 		sch:       sch,
 	}
-	testBuild(t, bctx, []assertion{
+	testBuild(t, bctx, false, []assertion{
 		assertGeneratedModule("go/modules/other/external_module.go", expected),
 	})
 }
@@ -174,7 +174,7 @@ func Call(context.Context, Req) (Resp, error) {
 		buildDir:  "_ftl",
 		sch:       sch,
 	}
-	testBuild(t, bctx, []assertion{
+	testBuild(t, bctx, false, []assertion{
 		assertGeneratedModule("go/modules/test/external_module.go", expected),
 	})
 }

buildengine/build_kotlin.go

@@ -2,6 +2,7 @@ package buildengine
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -13,8 +14,10 @@ import (
 	"github.com/beevik/etree"
 	sets "github.com/deckarep/golang-set/v2"
 	"golang.org/x/exp/maps"
+	"google.golang.org/protobuf/proto"
 
 	"github.com/TBD54566975/ftl"
+	schemapb "github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/schema"
 	"github.com/TBD54566975/ftl/backend/schema"
 	"github.com/TBD54566975/ftl/internal"
 	"github.com/TBD54566975/ftl/internal/exec"
@@ -59,7 +62,16 @@ func buildKotlinModule(ctx context.Context, sch *schema.Schema, module Module) e
 	logger.Debugf("Using build command '%s'", module.Build)
 	err := exec.Command(ctx, log.Debug, module.Dir, "bash", "-c", module.Build).RunBuffered(ctx)
 	if err != nil {
-		return fmt.Errorf("failed to build module %q: %w", module.Module, err)
+		// read runtime-specific build errors from the build directory
+		errorList, err := loadProtoErrors(module.AbsDeployDir())
+		if err != nil {
+			return fmt.Errorf("failed to read build errors for module: %w", err)
+		}
+		errs := make([]error, 0, len(errorList.Errors))
+		for _, e := range errorList.Errors {
+			errs = append(errs, *e)
+		}
+		return errors.Join(errs...)
 	}
 
 	return nil
@@ -249,3 +261,21 @@ func genType(module *schema.Module, t schema.Type) string {
 	}
 	panic(fmt.Sprintf("unsupported type %T", t))
 }
+
+func loadProtoErrors(buildDir string) (*schema.ErrorList, error) {
+	f := filepath.Join(buildDir, "errors.pb")
+	if _, err := os.Stat(f); errors.Is(err, os.ErrNotExist) {
+		return &schema.ErrorList{Errors: make([]*schema.Error, 0)}, nil
+	}
+
+	content, err := os.ReadFile(f)
+	if err != nil {
+		return nil, err
+	}
+	errorspb := &schemapb.ErrorList{}
+	err = proto.Unmarshal(content, errorspb)
+	if err != nil {
+		return nil, err
+	}
+	return schema.ErrorListFromProto(errorspb), nil
+}

buildengine/build_kotlin_test.go

@@ -1,15 +1,9 @@
 package buildengine
 
 import (
-	"bytes"
-	"context"
-	"os"
 	"testing"
 
-	"github.com/alecthomas/assert/v2"
-
 	"github.com/TBD54566975/ftl/backend/schema"
-	"github.com/TBD54566975/ftl/internal/log"
 )
 
 func TestGenerateBasicModule(t *testing.T) {
@@ -31,7 +25,7 @@ package ftl.test
 		buildDir:  "target",
 		sch:       sch,
 	}
-	testBuild(t, bctx, []assertion{
+	testBuild(t, bctx, false, []assertion{
 		assertGeneratedModule("generated-sources/ftl/test/Test.kt", expected),
 	})
 }
@@ -158,7 +152,7 @@ data class TestResponse(
 		buildDir:  "target",
 		sch:       sch,
 	}
-	testBuild(t, bctx, []assertion{
+	testBuild(t, bctx, false, []assertion{
 		assertGeneratedModule("generated-sources/ftl/test/Test.kt", expected),
 	})
 }
@@ -219,7 +213,7 @@ fun testVerb(context: Context, req: Request): ftl.builtin.Empty = throw
 		buildDir:  "target",
 		sch:       sch,
 	}
-	testBuild(t, bctx, []assertion{
+	testBuild(t, bctx, false, []assertion{
 		assertGeneratedModule("generated-sources/ftl/test/Test.kt", expected),
 	})
 }
@@ -273,7 +267,7 @@ class Empty
 		buildDir:  "target",
 		sch:       sch,
 	}
-	testBuild(t, bctx, []assertion{
+	testBuild(t, bctx, false, []assertion{
 		assertGeneratedModule("generated-sources/ftl/builtin/Builtin.kt", expected),
 	})
 }
@@ -317,7 +311,7 @@ fun emptyVerb(context: Context, req: ftl.builtin.Empty): ftl.builtin.Empty = thr
 		buildDir:  "target",
 		sch:       sch,
 	}
-	testBuild(t, bctx, []assertion{
+	testBuild(t, bctx, false, []assertion{
 		assertGeneratedModule("generated-sources/ftl/test/Test.kt", expected),
 	})
 }
@@ -397,7 +391,7 @@ fun nothing(context: Context): Unit = throw
 		buildDir:  "target",
 		sch:       sch,
 	}
-	testBuild(t, bctx, []assertion{
+	testBuild(t, bctx, false, []assertion{
 		assertGeneratedModule("generated-sources/ftl/test/Test.kt", expected),
 	})
 }
@@ -406,22 +400,12 @@ func TestKotlinExternalType(t *testing.T) {
 	if testing.Short() {
 		t.SkipNow()
 	}
-	moduleDir := "testdata/projects/externalkotlin"
-	buildDir := "_ftl"
-
-	ctx := log.ContextWithLogger(context.Background(), log.Configure(os.Stderr, log.Config{}))
-	module, err := LoadModule(moduleDir)
-	assert.NoError(t, err)
-
-	logBuffer := bytes.Buffer{}
-	logger := log.Configure(&logBuffer, log.Config{})
-	ctx = log.ContextWithLogger(ctx, logger)
-
-	sch := &schema.Schema{}
-	err = Build(ctx, sch, module)
-	assert.Error(t, err)
-	assert.Contains(t, logBuffer.String(), "Expected module name to be in the form ftl.<module>, but was com.google.type.DayOfWeek")
-
-	err = os.RemoveAll(buildDir)
-	assert.NoError(t, err, "Error removing build directory")
+	bctx := buildContext{
+		moduleDir: "testdata/projects/externalkotlin",
+		buildDir:  "target",
+		sch:       &schema.Schema{},
+	}
+	testBuild(t, bctx, true, []assertion{
+		assertBuildProtoErrors("expected module name to be in the form ftl.<module>, but was com.google.type.DayOfWeek"),
+	})
 }

buildengine/build_test.go

@@ -23,22 +23,28 @@ type assertion func(t testing.TB, bctx buildContext) error
 func testBuild(
 	t *testing.T,
 	bctx buildContext,
+	expectFail bool,
 	assertions []assertion,
 ) {
 	t.Helper()
 	ctx := log.ContextWithLogger(context.Background(), log.Configure(os.Stderr, log.Config{}))
-	module, err := LoadModule(bctx.moduleDir)
+	abs, err := filepath.Abs(bctx.moduleDir)
+	assert.NoError(t, err, "Error getting absolute path for module directory")
+	module, err := LoadModule(abs)
 	assert.NoError(t, err)
-
 	err = Build(ctx, bctx.sch, module)
-	assert.NoError(t, err)
+	if expectFail {
+		assert.Error(t, err)
+	} else {
+		assert.NoError(t, err)
+	}
 
 	for _, a := range assertions {
 		err = a(t, bctx)
 		assert.NoError(t, err)
 	}
 
-	err = os.RemoveAll(bctx.buildDir)
+	err = os.RemoveAll(filepath.Join(bctx.moduleDir, bctx.buildDir))
 	assert.NoError(t, err, "Error removing build directory")
 }
 
@@ -54,3 +60,24 @@ func assertGeneratedModule(generatedModulePath string, expectedContent string) a
 		return nil
 	}
 }
+
+func assertBuildProtoErrors(msgs ...string) assertion {
+	return func(t testing.TB, bctx buildContext) error {
+		t.Helper()
+		errorList, err := loadProtoErrors(filepath.Join(bctx.moduleDir, bctx.buildDir))
+		assert.NoError(t, err, "Error loading proto errors")
+
+		expected := make([]*schema.Error, 0, len(msgs))
+		for _, msg := range msgs {
+			expected = append(expected, &schema.Error{Msg: msg})
+		}
+
+		// normalize results
+		for _, e := range errorList.Errors {
+			e.EndColumn = 0
+		}
+
+		assert.Equal(t, errorList.Errors, expected, assert.Exclude[schema.Position]())
+		return nil
+	}
+}

internal/exec/exec.go

@@ -2,7 +2,6 @@ package exec
 
 import (
 	"context"
-	"fmt"
 	"os"
 	"os/exec" //nolint:depguard
 	"syscall"
@@ -59,7 +58,7 @@ func (c *Cmd) RunBuffered(ctx context.Context) error {
 
 	err := c.Run()
 	if err != nil {
-		fmt.Printf("%s", outputBuffer.Bytes())
+		log.FromContext(ctx).Infof("%s", outputBuffer.Bytes())
 		return err
 	}