fix(rfc2047): replace broken ccaf5a7 fix with workaround

src/headers/rfc2047.rs

@@ -28,18 +28,27 @@ const ENCODING_END_SUFFIX: &str = "?=";
 /// # }
 /// ```
 pub fn encode(mut s: &str, w: &mut EmailWriter<'_>) -> fmt::Result {
+    let mut wrote = false;
+
     while !s.is_empty() {
         let remaining_line_len = MAX_LINE_LEN.saturating_sub(
             ENCODING_START_PREFIX.len() + ENCODING_END_SUFFIX.len() + w.line_len() + "\r\n".len(),
         );
         let unencoded_remaining_line_len = remaining_line_len / 4 * 3;
 
-        let word = utils::truncate_to_char_boundary(s, unencoded_remaining_line_len.min(s.len()));
-
+        let mut word =
+            utils::truncate_to_char_boundary(s, unencoded_remaining_line_len.min(s.len()));
         if word.is_empty() {
-            // No space remaining on this line, go to a new one
-            w.new_line_and_space()?;
-            continue;
+            if wrote {
+                // No space remaining on this line, go to a new one
+                w.new_line()?;
+                w.space();
+                continue;
+            }
+
+            // No space remaining, but going to a new line will require us
+            // to introduce a new space, which will mess up things even more.
+            word = &s[..s.chars().next().unwrap().len_utf8()];
         }
 
         // Write the prefix
@@ -55,8 +64,8 @@ pub fn encode(mut s: &str, w: &mut EmailWriter<'_>) -> fmt::Result {
         // Write the suffix
         w.write_str(ENCODING_END_SUFFIX)?;
 
-        // Advance `s`
         s = &s[word.len()..];
+        wrote = true;
     }
 
     Ok(())

src/headers/writer.rs

@@ -53,17 +53,6 @@ impl<'a> EmailWriter<'a> {
         Ok(())
     }
 
-    /// Equivalent to calling `new_line()` and `space()` consecutively.
-    pub(crate) fn new_line_and_space(&mut self) -> fmt::Result {
-        self.spaces = 0;
-        self.writer.write_str("\r\n ")?;
-        self.line_len = 1;
-        self.optional_breakpoint = false;
-        self.can_go_to_new_line_now = false;
-
-        Ok(())
-    }
-
     #[cfg(not(tarpaulin_include))]
     #[doc(hidden)]
     #[deprecated(note = "Renamed to `new_line`", since = "0.1.2")]
@@ -76,6 +65,10 @@ impl<'a> EmailWriter<'a> {
         self.spaces += 1;
     }
 
+    pub(super) fn has_spaces(&self) -> bool {
+        self.spaces > 0
+    }
+
     /// Write a space which won't be printed if the line wraps.
     ///
     /// This method shouldn't be called multiple times consecutively,
@@ -367,8 +360,8 @@ mod tests {
         assert_eq!(
             s,
             concat!(
-                "Subject: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA BBBBBBBBBBBBB\r\n",
-                " =?utf-8?b?c8OpbGVjdGlvbg==?=",
+                "Subject: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA BBBBBBBBBBBBB =?utf-8?b?cw==?=\r\n",
+                " =?utf-8?b?w6lsZWN0aW9u?=",
             )
         );
     }