Document and test UrlPartsBuilder::push_fmt

src/librustdoc/html/url_parts_builder.rs

@@ -67,6 +67,19 @@ impl UrlPartsBuilder {
         self.buf.push_str(part);
     }
 
+    /// Push a component onto the buffer, using [`format!`]'s formatting syntax.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage (equivalent to the example for [`UrlPartsBuilder::push`]):
+    ///
+    /// ```ignore (private-type)
+    /// let mut builder = UrlPartsBuilder::new();
+    /// builder.push("core");
+    /// builder.push("str");
+    /// builder.push_fmt(format_args!("{}.{}.html", "struct", "Bytes"));
+    /// assert_eq!(builder.finish(), "core/str/struct.Bytes.html");
+    /// ```
     crate fn push_fmt(&mut self, args: fmt::Arguments<'_>) {
         if !self.buf.is_empty() {
             self.buf.push('/');

src/librustdoc/html/url_parts_builder/tests.rs

@@ -40,6 +40,16 @@ fn push_front_non_empty() {
     t(builder, "nightly/core/str/struct.Bytes.html");
 }
 
+#[test]
+fn push_fmt() {
+    let mut builder = UrlPartsBuilder::new();
+    builder.push_fmt(format_args!("{}", "core"));
+    builder.push("str");
+    builder.push_front("nightly");
+    builder.push_fmt(format_args!("{}.{}.html", "struct", "Bytes"));
+    t(builder, "nightly/core/str/struct.Bytes.html");
+}
+
 #[test]
 fn collect() {
     t(["core", "str"].into_iter().collect(), "core/str");