[rust] Make enum names public (#5690)

* Bugfix for Rust generation of union fields named with language keywords

Looking at ParseField, it appears that in the case of unions, an extra field with a `UnionTypeFieldSuffix` is added to the type definition, however, if the name of this field is a keyword in the target language, it isn't escaped.

For example, if generating code for rust for a union field named `type`, flatc will generate a (non-keyword escaped) field named `type_type` for this hidden union field, and one (keyword escaped) called `type_` for the actual union contents.

When the union accessors are generated, they refer to this `type_type` field, but they will escape it mistakenly, generating code like this:

```
  #[inline]
  #[allow(non_snake_case)]
  pub fn type__as_int(&self) -> Option<Int<'a>> {
    if self.type__type() == Type::Int {
      self.type_().map(|u| Int::init_from_table(u))
    } else {
      None
    }
  }
```

Which will fail to build because the field is called `self.type_type()`, not `self.type__type()`.

* [Rust] Add crate-relative use statements for FBS includes.

At present if a flatbuffer description includes a reference to a type in
another file, the generated Rust code needs to be hand-modified to add
the appropriate `use` statements.

This assumes that the dependencies are built into the same crate, which
I think is a reasonable assumption?

* Revert "[Rust] Add crate-relative use statements for FBS includes."

This reverts commit d554d79fec.

* Address comments raised in PR

* Update documentation comments per feedback

* Fix typo

* [rust] Make enum variant names public.

* Update generated test files

* Add test for public enum names

src/idl_gen_rust.cpp

@@ -621,7 +621,7 @@ class RustGenerator : public BaseGenerator {
     static const uint64_t kMaxSparseness = 5;
     if (range / static_cast<uint64_t>(enum_def.size()) < kMaxSparseness) {
       code_ += "#[allow(non_camel_case_types)]";
-      code_ += "const ENUM_NAMES_{{ENUM_NAME_CAPS}}:[&'static str; " +
+      code_ += "pub const ENUM_NAMES_{{ENUM_NAME_CAPS}}:[&'static str; " +
                NumToString(range + 1) + "] = [";
 
       auto val = enum_def.Vals().front();

tests/monster_test_generated.rs

@@ -219,7 +219,7 @@ pub const ENUM_VALUES_COLOR:[Color; 3] = [
 ];
 
 #[allow(non_camel_case_types)]
-const ENUM_NAMES_COLOR:[&'static str; 8] = [
+pub const ENUM_NAMES_COLOR:[&'static str; 8] = [
     "Red",
     "Green",
     "",
@@ -289,7 +289,7 @@ pub const ENUM_VALUES_RACE:[Race; 4] = [
 ];
 
 #[allow(non_camel_case_types)]
-const ENUM_NAMES_RACE:[&'static str; 4] = [
+pub const ENUM_NAMES_RACE:[&'static str; 4] = [
     "None",
     "Human",
     "Dwarf",
@@ -355,7 +355,7 @@ pub const ENUM_VALUES_ANY:[Any; 4] = [
 ];
 
 #[allow(non_camel_case_types)]
-const ENUM_NAMES_ANY:[&'static str; 4] = [
+pub const ENUM_NAMES_ANY:[&'static str; 4] = [
     "NONE",
     "Monster",
     "TestSimpleTableWithEnum",
@@ -422,7 +422,7 @@ pub const ENUM_VALUES_ANY_UNIQUE_ALIASES:[AnyUniqueAliases; 4] = [
 ];
 
 #[allow(non_camel_case_types)]
-const ENUM_NAMES_ANY_UNIQUE_ALIASES:[&'static str; 4] = [
+pub const ENUM_NAMES_ANY_UNIQUE_ALIASES:[&'static str; 4] = [
     "NONE",
     "M",
     "TS",
@@ -489,7 +489,7 @@ pub const ENUM_VALUES_ANY_AMBIGUOUS_ALIASES:[AnyAmbiguousAliases; 4] = [
 ];
 
 #[allow(non_camel_case_types)]
-const ENUM_NAMES_ANY_AMBIGUOUS_ALIASES:[&'static str; 4] = [
+pub const ENUM_NAMES_ANY_AMBIGUOUS_ALIASES:[&'static str; 4] = [
     "NONE",
     "M1",
     "M2",

tests/namespace_test/namespace_test1_generated.rs

@@ -77,7 +77,7 @@ pub const ENUM_VALUES_ENUM_IN_NESTED_NS:[EnumInNestedNS; 3] = [
 ];
 
 #[allow(non_camel_case_types)]
-const ENUM_NAMES_ENUM_IN_NESTED_NS:[&'static str; 3] = [
+pub const ENUM_NAMES_ENUM_IN_NESTED_NS:[&'static str; 3] = [
     "A",
     "B",
     "C"

tests/rust_usage_test/tests/integration_test.rs

@@ -245,6 +245,16 @@ mod generated_constants {
             my_game::example::Color::Green,
             my_game::example::Color::Blue,
         ]);
+        assert_eq!(my_game::example::ENUM_NAMES_COLOR, [
+            "Red",
+            "Green",
+            "",
+            "",
+            "",
+            "",
+            "",
+            "Blue"
+        ]);
 
         assert_eq!(-1, my_game::example::ENUM_MIN_RACE);
         assert_eq!(2, my_game::example::ENUM_MAX_RACE);
@@ -254,6 +264,12 @@ mod generated_constants {
             my_game::example::Race::Dwarf,
             my_game::example::Race::Elf,
         ]);
+        assert_eq!(my_game::example::ENUM_NAMES_RACE, [
+            "None",
+            "Human",
+            "Dwarf",
+            "Elf"
+        ]);
 
         assert_eq!(0, my_game::example::ENUM_MIN_ANY);
         assert_eq!(3, my_game::example::ENUM_MAX_ANY);
@@ -263,6 +279,12 @@ mod generated_constants {
             my_game::example::Any::TestSimpleTableWithEnum,
             my_game::example::Any::MyGame_Example2_Monster,
         ]);
+        assert_eq!(my_game::example::ENUM_NAMES_ANY, [
+            "NONE",
+            "Monster",
+            "TestSimpleTableWithEnum",
+            "MyGame_Example2_Monster"
+        ]);
 
         assert_eq!(0, my_game::example::ENUM_MIN_ANY_UNIQUE_ALIASES);
         assert_eq!(3, my_game::example::ENUM_MAX_ANY_UNIQUE_ALIASES);
@@ -272,6 +294,12 @@ mod generated_constants {
             my_game::example::AnyUniqueAliases::TS,
             my_game::example::AnyUniqueAliases::M2,
         ]);
+        assert_eq!(my_game::example::ENUM_NAMES_ANY_UNIQUE_ALIASES, [
+            "NONE",
+            "M",
+            "TS",
+            "M2"
+        ]);
 
         assert_eq!(0, my_game::example::ENUM_MIN_ANY_AMBIGUOUS_ALIASES);
         assert_eq!(3, my_game::example::ENUM_MAX_ANY_AMBIGUOUS_ALIASES);
@@ -281,6 +309,12 @@ mod generated_constants {
             my_game::example::AnyAmbiguousAliases::M2,
             my_game::example::AnyAmbiguousAliases::M3,
         ]);
+        assert_eq!(my_game::example::ENUM_NAMES_ANY_AMBIGUOUS_ALIASES, [
+            "NONE",
+            "M1",
+            "M2",
+            "M3"
+        ]);
     }
 }