librustdoc: create MaybeDisplay helper for Option<T: Display> types

src/librustdoc/clean/cfg.rs

@@ -13,8 +13,8 @@ use rustc_session::parse::ParseSess;
 use rustc_span::Span;
 use rustc_span::symbol::{Symbol, sym};
 
+use crate::display::Joined as _;
 use crate::html::escape::Escape;
-use crate::joined::Joined as _;
 
 #[cfg(test)]
 mod tests;

src/librustdoc/display.rs

@@ -1,3 +1,5 @@
+//! Various utilities for working with [`fmt::Display`] implementations.
+
 use std::fmt::{self, Display, Formatter};
 
 pub(crate) trait Joined: IntoIterator {
@@ -27,3 +29,19 @@ where
         Ok(())
     }
 }
+
+pub(crate) trait MaybeDisplay {
+    /// For a given `Option<T: Display>`, returns a `Display` implementation that will display `t` if `Some(t)`, or nothing if `None`.
+    fn maybe_display(self) -> impl Display;
+}
+
+impl<T: Display> MaybeDisplay for Option<T> {
+    fn maybe_display(self) -> impl Display {
+        fmt::from_fn(move |f| {
+            if let Some(t) = self.as_ref() {
+                t.fmt(f)?;
+            }
+            Ok(())
+        })
+    }
+}

src/librustdoc/html/format.rs

@@ -30,11 +30,11 @@ use super::url_parts_builder::{UrlPartsBuilder, estimate_item_path_byte_length};
 use crate::clean::types::ExternalLocation;
 use crate::clean::utils::find_nearest_parent_module;
 use crate::clean::{self, ExternalCrate, PrimitiveType};
+use crate::display::Joined as _;
 use crate::formats::cache::Cache;
 use crate::formats::item_type::ItemType;
 use crate::html::escape::{Escape, EscapeBodyText};
 use crate::html::render::Context;
-use crate::joined::Joined as _;
 use crate::passes::collect_intra_doc_links::UrlFragment;
 
 pub(crate) fn write_str(s: &mut String, f: fmt::Arguments<'_>) {

src/librustdoc/html/render/print_item.rs

@@ -27,6 +27,7 @@ use super::{
 };
 use crate::clean;
 use crate::config::ModuleSorting;
+use crate::display::Joined as _;
 use crate::formats::Impl;
 use crate::formats::item_type::ItemType;
 use crate::html::escape::{Escape, EscapeBodyTextWithWbr};
@@ -37,7 +38,6 @@ use crate::html::format::{
 use crate::html::markdown::{HeadingOffset, MarkdownSummaryLine};
 use crate::html::render::{document_full, document_item_info};
 use crate::html::url_parts_builder::UrlPartsBuilder;
-use crate::joined::Joined as _;
 
 /// Generates a Rinja template struct for rendering items with common methods.
 ///

src/librustdoc/lib.rs

@@ -106,6 +106,7 @@ macro_rules! map {
 mod clean;
 mod config;
 mod core;
+mod display;
 mod docfs;
 mod doctest;
 mod error;
@@ -114,7 +115,6 @@ mod fold;
 mod formats;
 // used by the error-index generator, so it needs to be public
 pub mod html;
-mod joined;
 mod json;
 pub(crate) mod lint;
 mod markdown;