Delete arrays as a compiler option.

Summary:
#What?
Delete `arrays` as a compiler option.

#Why?
`arrays` are now the default in the absence of `legacy_arrays` and `hack_collections`, and cease to exist as an explicit option.

# Fixtures
- Delete `arrays` from `cmd` files.
- Generated fixtures must not change.

# Context
`arraysets`, `no_use_hack_collections`, `stricttypes`, `array_migration`, `shape_arraykeys`, `const_collections` are all compiler options that control the generation of container fields. To make code generator simpler and easier to reason about, identify which of these can be removed/merged.

The new options based on the ones that are currently in use:

`legacy_arrays` replaces `no_use_hack_collections`.
`hack_collections`, which was the implicit default in the absence of `arrays` and `no_use_hack_collections`, is now explicit.
`arrays` are now the default in the absence of `legacy_arrays` and `hack_collections`, and cease to exist as an explicit option.

# The steps
The item in bold corresponds to the current diff.
1. Use new compiler options based on the ones that already exist.
1. Make arrays the default option.
1. Use the legacy arrays + hack collections logical equivalent of arrays.
1. Introduce hack collections wherever necessary.
1. Replace no use hack collections with legacy arrays.
1. Remove arraysets if arrays present.
1. Rename `no_use_hack_collections` compiler option to `legacy_arrays`.
1. Add `hack_collections` compiler option.
1. Remove references to the `arrays` compiler option.
1. **Delete the `arrays` compiler option.**

Reviewed By: rmakheja

Differential Revision: D67618067

fbshipit-source-id: d6c20bd9343f868b1492497f8e41b72ec91c45a6

thrift/compiler/generate/t_hack_generator.cc

@@ -124,7 +124,6 @@ class t_hack_generator : public t_concat_generator {
     shapes_allow_unknown_fields_ =
         option_is_specified(options, "shapes_allow_unknown_fields");
     array_migration_ = option_is_specified(options, "array_migration");
-    arrays_ = option_is_specified(options, "arrays");
     legacy_arrays_ = option_is_specified(options, "legacy_arrays");
     hack_collections_ = option_is_specified(options, "hack_collections");
 
@@ -1185,11 +1184,6 @@ class t_hack_generator : public t_concat_generator {
    */
   bool array_migration_;
 
-  /**
-   * True to use Hack arrays instead of collections
-   */
-  bool arrays_;
-
   /**
    * True to never use hack collection objects. Only used for migrations
    */
@@ -7632,8 +7626,6 @@ THRIFT_REGISTER_GENERATOR(
     "    shapes_allow_unknown_fields Allow unknown fields and implicit "
     "subtyping for shapes \n"
     "    frommap_construct Generate fromMap_DEPRECATED method.\n"
-    "    arrays           Use Hack arrays for maps/lists/sets instead of "
-    "objects.\n"
     "    hack_collections Generate hack collections instead of hack arrays.\n"
     "    const_collections Use ConstCollection objects rather than their "
     "mutable counterparts.\n"

thrift/compiler/test/fixtures/array_shape_arraykey/cmd

@@ -1 +1 @@
-hack: hack:arrays=1,shapes=1,shape_arraykeys=1 src/module.thrift
+hack: hack:shapes=1,shape_arraykeys=1 src/module.thrift

thrift/compiler/test/fixtures/hack-arrays/cmd

@@ -1 +1 @@
-hack: hack:arrays=1 src/module.thrift
+hack: hack src/module.thrift

thrift/compiler/test/fixtures/hack_field_wrapper_with_arrays/cmd

@@ -1,4 +1,4 @@
-hack: hack:json,arrays,shapes,shape_arraykeys,frommap_construct,typedef,server,shapes_use_pipe_structure src/module.thrift
-hack_include: hack:json,arrays,shapes,shape_arraykeys,frommap_construct,typedef,server,shapes_use_pipe_structure src/include.thrift
-hack_annotations: hack:json,arrays,shapes,shape_arraykeys,frommap_construct,typedef,server,shapes_use_pipe_structure src/annotations.thrift
-hack_constants: hack:json,arrays,shapes,shape_arraykeys,frommap_construct,typedef,server,shapes_use_pipe_structure src/constants.thrift
+hack: hack:json,shapes,shape_arraykeys,frommap_construct,typedef,server,shapes_use_pipe_structure src/module.thrift
+hack_include: hack:json,shapes,shape_arraykeys,frommap_construct,typedef,server,shapes_use_pipe_structure src/include.thrift
+hack_annotations: hack:json,shapes,shape_arraykeys,frommap_construct,typedef,server,shapes_use_pipe_structure src/annotations.thrift
+hack_constants: hack:json,shapes,shape_arraykeys,frommap_construct,typedef,server,shapes_use_pipe_structure src/constants.thrift

thrift/compiler/test/fixtures/lazy_constants/cmd

@@ -1,2 +1,2 @@
-hack: hack:lazy_constants=1,arrays=1 src/module.thrift
+hack: hack:lazy_constants=1 src/module.thrift
 java: mstch_java src/module.thrift

thrift/compiler/test/fixtures/shape_hack_arrays/cmd

@@ -1 +1 @@
-hack: hack:shapes=1,shapes_allow_unknown_fields=1,arrays=1,shapes_use_pipe_structure=1 src/module.thrift
+hack: hack:shapes=1,shapes_allow_unknown_fields=1,shapes_use_pipe_structure=1 src/module.thrift