refactor: move build errors out of schema

backend/protos/xyz/block/ftl/v1/language/language.proto

@@ -0,0 +1,25 @@
+syntax = "proto3";
+
+package xyz.block.ftl.v1.language;
+
+import "xyz/block/ftl/v1/schema/schema.proto";
+
+option go_package = "github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/language;languagepb";
+option java_multiple_files = true;
+
+message Error {
+  enum ErrorLevel {
+    INFO = 0;
+    WARN = 1;
+    ERROR = 2;
+  }
+
+  string msg = 1;
+  schema.Position pos = 2;
+  int64 endColumn = 3;
+  ErrorLevel level = 4;
+}
+
+message ErrorList {
+  repeated Error errors = 1;
+}

backend/protos/xyz/block/ftl/v1/language/mixins.go

@@ -0,0 +1,64 @@
+package languagepb
+
+import (
+	"fmt"
+
+	schemapb "github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/schema"
+	"github.com/TBD54566975/ftl/backend/schema"
+	"github.com/TBD54566975/ftl/internal/builderrors"
+	"github.com/TBD54566975/ftl/internal/slices"
+)
+
+// ErrorsFromProto converts a protobuf ErrorList to a []builderrors.Error.
+func ErrorsFromProto(e *ErrorList) []builderrors.Error {
+	return slices.Map(e.Errors, errorFromProto)
+}
+
+func ErrorsToProto(errs []builderrors.Error) *ErrorList {
+	return &ErrorList{Errors: slices.Map(errs, errorToProto)}
+}
+
+func levelFromProto(level Error_ErrorLevel) builderrors.ErrorLevel {
+	switch level {
+	case Error_INFO:
+		return builderrors.INFO
+	case Error_WARN:
+		return builderrors.WARN
+	case Error_ERROR:
+		return builderrors.ERROR
+	}
+	panic(fmt.Sprintf("unhandled ErrorLevel %v", level))
+}
+
+func levelToProto(level builderrors.ErrorLevel) Error_ErrorLevel {
+	switch level {
+	case builderrors.INFO:
+		return Error_INFO
+	case builderrors.WARN:
+		return Error_WARN
+	case builderrors.ERROR:
+		return Error_ERROR
+	}
+	panic(fmt.Sprintf("unhandled ErrorLevel %v", level))
+}
+
+func errorFromProto(e *Error) builderrors.Error {
+	return builderrors.Error{
+		Pos:   schema.PosFromProto(e.Pos).ToErrorPosWithEnd(int(e.EndColumn)),
+		Msg:   e.Msg,
+		Level: levelFromProto(e.Level),
+	}
+}
+
+func errorToProto(e builderrors.Error) *Error {
+	return &Error{
+		Msg: e.Msg,
+		Pos: &schemapb.Position{
+			Filename: e.Pos.Filename,
+			Column:   int64(e.Pos.StartColumn),
+			Line:     int64(e.Pos.Line),
+		},
+		EndColumn: int64(e.Pos.EndColumn),
+		Level:     levelToProto(e.Level),
+	}
+}