some more docs

calibre-db/src/data/book.rs

@@ -39,25 +39,34 @@ pub struct AuthorBooksError {
 }
 
 #[derive(Debug, Snafu)]
+/// Errors that can occur when fetching a series' books.
 pub enum SeriesBookError {
+    /// A failure to prepare the SQL statement.
     #[snafu(display("Failed to prepare statement."))]
     PrepareSeriesBook { source: rusqlite::Error },
+    /// A failure to execute the SQL statement.
     #[snafu(display("Failed to execute statement."))]
     ExecuteSeriesBook { source: rusqlite::Error },
 }
 
 #[derive(Debug, Snafu)]
+/// Errors that can occur when fetching recent books.
 pub enum RecentBooksError {
+    /// A failure to prepare the SQL statement.
     #[snafu(display("Failed to prepare statement."))]
     PrepareRecentBooks { source: rusqlite::Error },
+    /// A failure to execute the SQL statement.
     #[snafu(display("Failed to execute statement."))]
     ExecuteRecentBooks { source: rusqlite::Error },
 }
 
 #[derive(Debug, Snafu)]
+/// Errors that can occur when fetching a single book.
 pub enum ScalarBookError {
+    /// A failure to prepare the SQL statement.
     #[snafu(display("Failed to prepare statement."))]
     PrepareScalarBook { source: rusqlite::Error },
+    /// A failure to execute the SQL statement.
     #[snafu(display("Failed to execute statement."))]
     ExecuteScalarBook { source: rusqlite::Error },
 }
@@ -75,6 +84,7 @@ pub struct MoreBooksError {
 }
 
 impl Book {
+    /// Create a book from a database row.
     fn from_row(row: &Row<'_>) -> Result<Self, rusqlite::Error> {
         Ok(Self {
             id: row.get(0)?,