Manually mention required features

src/engine.rs

@@ -1697,6 +1697,9 @@ impl Reedline {
     }
 
     /// Adds an external printer
+    ///
+    /// ## Required feature:
+    /// `external_printer`
     #[cfg(feature = "external_printer")]
     pub fn with_external_printer(mut self, printer: ExternalPrinter<String>) -> Self {
         self.external_printer = Some(printer);

src/external_printer.rs

@@ -17,6 +17,9 @@ pub const EXTERNAL_PRINTER_DEFAULT_CAPACITY: usize = 20;
 /// An ExternalPrinter allows to print messages of text while editing a line.
 /// The message is printed as a new line, the line-edit will continue below the
 /// output.
+///
+/// ## Required feature:
+/// `external_printer`
 #[cfg(feature = "external_printer")]
 #[derive(Debug, Clone)]
 pub struct ExternalPrinter<T>

src/history/sqlite_backed.rs

@@ -14,6 +14,9 @@ const SQLITE_APPLICATION_ID: i32 = 1151497937;
 /// A history that stores the values to an SQLite database.
 /// In addition to storing the command, the history can store an additional arbitrary HistoryEntryContext,
 /// to add information such as a timestamp, running directory, result...
+///
+/// ## Required feature:
+/// `sqlite` or `sqlite-dynlib`
 pub struct SqliteBackedHistory {
     db: rusqlite::Connection,
     session: Option<HistorySessionId>,