Run plugin with asserts when building test protos (#1055)

Currently we run the tests with assertions but that doesn't cover some of the
code paths.

When building the test protos we don't run the plugin with assertions.

Add a new executable `protoc-gen-dart-debug` that is the same as
`protoc-gen-dart`, but passes `--enable-asserts` to Dart. Use it when building
test protos.

This triggers an assertion which was reported in #608. The assertion is clearly
wrong (we call the function for repeated fields a few lines above the
assertion) and no one knows or remembers why it's there. Remove the assertion.

Closes #608.

Author: osa1

protoc_plugin/Makefile

@@ -3,7 +3,7 @@ PLUGIN_SRC = \
 	lib/**/*.dart
 
 OUTPUT_DIR=test/gen
-PLUGIN_NAME=protoc-gen-dart
+PLUGIN_NAME=protoc-gen-dart-debug
 PLUGIN_PATH=bin/$(PLUGIN_NAME)
 
 TEST_PROTO_LIST = \

protoc_plugin/bin/protoc-gen-dart-debug

@@ -0,0 +1,3 @@
+#!/bin/bash
+BINDIR=$(dirname "$0")
+dart --enable-asserts "$BINDIR/protoc_plugin.dart" -c "$@"

protoc_plugin/lib/src/protobuf_field.dart

@@ -393,7 +393,6 @@ class ProtobufField {
 
   /// Returns a function expression that returns the field's default value.
   String? generateDefaultFunction({bool omitIfFirstEnumValue = false}) {
-    assert(!isRepeated);
     switch (descriptor.type) {
       case FieldDescriptorProto_Type.TYPE_BOOL:
         return _getDefaultAsBoolExpr(null);