Always use whisker for rendering code

Summary: Everything is using whisker now. Goodbye `mstch::render`!

Reviewed By: createdbysk

Differential Revision: D67954314

fbshipit-source-id: 00b861895d149169553ce44f7625f1ba80b644f9

thrift/compiler/generate/t_json_experimental_generator.cc

@@ -56,10 +56,6 @@ class t_json_experimental_generator : public t_mstch_generator {
  public:
   using t_mstch_generator::t_mstch_generator;
 
-  std::optional<whisker_options> use_whisker() const override {
-    return whisker_options();
-  }
-
   std::string template_prefix() const override { return "json"; }
 
   void generate_program() override;

thrift/compiler/generate/t_mstch_cpp2_generator.cc

@@ -269,7 +269,7 @@ class t_mstch_cpp2_generator : public t_mstch_generator {
  public:
   using t_mstch_generator::t_mstch_generator;
 
-  std::optional<whisker_options> use_whisker() const override {
+  whisker_options render_options() const override {
     whisker_options opts;
     opts.allowed_undefined_variables = {
         "program:autogen_path",

thrift/compiler/generate/t_mstch_generator.cc

@@ -575,38 +575,17 @@ t_mstch_generator::gen_whisker_render_state(whisker_options whisker_opts) {
 
 std::string t_mstch_generator::render(
     const std::string& template_name, const mstch::node& context) {
-  if (std::holds_alternative<std::monostate>(whisker_render_state_)) {
-    auto whisker_requested = use_whisker();
-    whisker_render_state_ = whisker_requested
-        ? gen_whisker_render_state(*whisker_requested)
-        : std::optional<whisker_render_state>();
-  }
-  auto& render_state =
-      std::get<std::optional<whisker_render_state>>(whisker_render_state_);
-
-  if (!render_state.has_value()) {
-    // The implementation chose not to use Whisker.
-
-    // Remove the template prefix from the template map
-    std::map<std::string, std::string> partials;
-    auto prefix = template_prefix() + '/';
-    for (const auto& [k, v] : get_template_map()) {
-      if (k.substr(0, prefix.size()) == prefix) {
-        partials[k.substr(prefix.size())] = v;
-      }
-    }
-
-    return mstch::render(
-        get_template(prefix + template_name), context, partials);
+  if (!whisker_render_state_.has_value()) {
+    whisker_render_state_ = gen_whisker_render_state(render_options());
   }
 
   std::vector<std::string> partial_path;
   boost::algorithm::split(
       partial_path, template_name, [](char c) { return c == '/'; });
 
   std::optional<whisker::ast::root> ast =
-      render_state->template_resolver->resolve(
-          partial_path, {}, render_state->diagnostic_engine);
+      whisker_render_state_->template_resolver->resolve(
+          partial_path, {}, whisker_render_state_->diagnostic_engine);
   if (!ast.has_value()) {
     throw std::runtime_error{
         fmt::format("Could not find template \"{}\"", template_name)};
@@ -617,8 +596,8 @@ std::string t_mstch_generator::render(
           out,
           *ast,
           whisker::from_mstch(context),
-          render_state->diagnostic_engine,
-          render_state->render_options)) {
+          whisker_render_state_->diagnostic_engine,
+          whisker_render_state_->render_options)) {
     throw std::runtime_error{
         fmt::format("Failed to render template \"{}\"", template_name)};
   }

thrift/compiler/generate/t_mstch_generator.h

@@ -59,11 +59,9 @@ class t_mstch_generator : public t_generator {
     std::unordered_set<std::string> allowed_undefined_variables;
   };
   /**
-   * If true, uses the Whisker template engine instead of Mustache.
+   * Customization point for Whisker's rendering options.
    */
-  virtual std::optional<whisker_options> use_whisker() const {
-    return std::nullopt;
-  }
+  virtual whisker_options render_options() const { return {}; }
 
   /**
    * If true, typedefs will be automatically resolved to their underlying type.
@@ -237,12 +235,7 @@ class t_mstch_generator : public t_generator {
     std::shared_ptr<whisker::template_resolver> template_resolver;
     whisker::render_options render_options;
   };
-  // std::monostate implies that we have not yet checked if the implemented
-  // requested the use of Whisker.
-  // empty optional implies that we have checked and the implementation is NOT
-  // using Whisker.
-  std::variant<std::monostate, std::optional<whisker_render_state>>
-      whisker_render_state_;
+  std::optional<whisker_render_state> whisker_render_state_;
   whisker_render_state gen_whisker_render_state(whisker_options);
 
   /**

thrift/compiler/generate/t_mstch_go_generator.cc

@@ -45,7 +45,7 @@ class t_mstch_go_generator : public t_mstch_generator {
  public:
   using t_mstch_generator::t_mstch_generator;
 
-  std::optional<whisker_options> use_whisker() const override {
+  whisker_options render_options() const override {
     whisker_options opts;
     opts.allowed_undefined_variables = {
         "service:autogen_path",

thrift/compiler/generate/t_mstch_html_generator.cc

@@ -22,12 +22,6 @@ class t_mstch_html_generator : public t_mstch_generator {
  public:
   using t_mstch_generator::t_mstch_generator;
 
-  std::optional<whisker_options> use_whisker() const override {
-    whisker_options opts;
-    opts.allowed_undefined_variables = {};
-    return opts;
-  }
-
   std::string template_prefix() const override { return "html"; }
 
   void generate_program() override {

thrift/compiler/generate/t_mstch_java_generator.cc

@@ -159,7 +159,7 @@ class t_mstch_java_generator : public t_mstch_generator {
  public:
   using t_mstch_generator::t_mstch_generator;
 
-  std::optional<whisker_options> use_whisker() const override {
+  whisker_options render_options() const override {
     whisker_options opts;
     opts.allowed_undefined_variables = {
         "type:typedef_type", // in UnionWrite.mustache

thrift/compiler/generate/t_mstch_py3_generator.cc

@@ -1379,7 +1379,7 @@ class t_mstch_py3_generator : public t_mstch_generator {
  public:
   using t_mstch_generator::t_mstch_generator;
 
-  std::optional<whisker_options> use_whisker() const override {
+  whisker_options render_options() const override {
     whisker_options opts;
     opts.allowed_undefined_variables = {
         "service:autogen_path", "function:stream?"};

thrift/compiler/generate/t_mstch_pyi_generator.cc

@@ -554,7 +554,7 @@ class t_mstch_pyi_generator : public t_mstch_generator {
  public:
   using t_mstch_generator::t_mstch_generator;
 
-  std::optional<whisker_options> use_whisker() const override {
+  whisker_options render_options() const override {
     whisker_options opts;
     opts.allowed_undefined_variables = {
         "service:autogen_path",

thrift/compiler/generate/t_mstch_python_capi_generator.cc

@@ -659,10 +659,6 @@ class t_mstch_python_capi_generator : public t_mstch_generator {
  public:
   using t_mstch_generator::t_mstch_generator;
 
-  std::optional<whisker_options> use_whisker() const override {
-    return whisker_options();
-  }
-
   std::string template_prefix() const override { return "python_capi"; }
 
   void generate_program() override {

thrift/compiler/generate/t_mstch_python_generator.cc

@@ -1125,7 +1125,7 @@ class t_mstch_python_generator : public t_mstch_generator {
  public:
   using t_mstch_generator::t_mstch_generator;
 
-  std::optional<whisker_options> use_whisker() const override {
+  whisker_options render_options() const override {
     whisker_options opts;
     opts.allowed_undefined_variables = {
         "field:has_adapter?",
@@ -1535,7 +1535,7 @@ class t_python_patch_generator : public t_mstch_generator {
  public:
   using t_mstch_generator::t_mstch_generator;
 
-  std::optional<whisker_options> use_whisker() const override {
+  whisker_options render_options() const override {
     whisker_options opts;
     opts.allowed_undefined_variables = {
         "field:has_adapter?",

thrift/compiler/generate/t_mstch_rust_generator.cc

@@ -619,7 +619,7 @@ class t_mstch_rust_generator : public t_mstch_generator {
  public:
   using t_mstch_generator::t_mstch_generator;
 
-  std::optional<whisker_options> use_whisker() const override {
+  whisker_options render_options() const override {
     whisker_options opts;
     opts.allowed_undefined_variables = {
         "typedef:newtype?",