Add support to generate documentation for tests

Author: lucagladiator

src/librustdoc/config.rs

@@ -163,6 +163,9 @@ pub(crate) struct Options {
     /// the compiler will scrape examples and not generate documentation.
     pub(crate) scrape_examples_options: Option<ScrapeExamplesOptions>,
 
+    /// Whether to generate documentation for tests.
+    pub(crate) document_tests: bool,
+
     /// Note: this field is duplicated in `RenderOptions` because it's useful
     /// to have it in both places.
     pub(crate) unstable_features: rustc_feature::UnstableFeatures,
@@ -216,6 +219,7 @@ impl fmt::Debug for Options {
             .field("remap-file-prefix", &self.remap_path_prefix)
             .field("nocapture", &self.nocapture)
             .field("scrape_examples_options", &self.scrape_examples_options)
+            .field("document_tests", &self.document_tests)
             .field("unstable_features", &self.unstable_features)
             .finish()
     }
@@ -820,6 +824,7 @@ impl Options {
             output_format,
             json_unused_externs,
             scrape_examples_options,
+            document_tests,
             unstable_features,
             expanded_args: args,
         };