From 3cf2748c30b5bab6f7b307a488706e76c3188a28 Mon Sep 17 00:00:00 2001
From: Thomas Oettli <spacefreak@noop.ch>
Date: Sun, 11 Oct 2026 00:12:42 +0200
Subject: [PATCH] make encode_header_value and default_conditional
 crate-private

---
 src/header/encoding.rs | 14 ++------------
 src/header/mod.rs      | 10 +++++-----
 src/lib.rs             |  8 ++++----
 src/tests.rs           |  9 +++++++++
 4 files changed, 20 insertions(+), 21 deletions(-)

diff --git a/src/header/encoding.rs b/src/header/encoding.rs
index 1e72a04..376eec4 100644
--- a/src/header/encoding.rs
+++ b/src/header/encoding.rs
@@ -38,18 +38,8 @@ fn encode(encode_buf: &mut String, writer: &mut EmailWriter) {
 /// `key` itself is not part of the result: only its length matters, for the length of the first
 /// line.
 ///
-/// # Examples
-///
-/// ```
-/// use cow_mail::header::encode_header_value;
-///
-/// // Plain text is left alone.
-/// assert_eq!(encode_header_value("Subject", "a test"), "a test");
-///
-/// // Only the words that need it are encoded.
-/// assert_eq!(encode_header_value("Subject", "Grüße"), "=?utf-8?b?R3LDvMOfZQ==?=");
-/// ```
-pub fn encode_header_value(key: &str, value: &str) -> String {
+/// Pinned by `test_encode_header_value` in `src/tests.rs`.
+pub(crate) fn encode_header_value(key: &str, value: &str) -> String {
     let mut encoded_value = String::new();
     let line_len = key.len() + ": ".len();
     let mut writer = EmailWriter::new(&mut encoded_value, line_len, 0, false);
diff --git a/src/header/mod.rs b/src/header/mod.rs
index 60a44bb..a74550f 100644
--- a/src/header/mod.rs
+++ b/src/header/mod.rs
@@ -11,7 +11,7 @@
 mod encoding;
 mod headers;
 
-pub use encoding::encode_header_value;
+pub(crate) use encoding::encode_header_value;
 pub(crate) use headers::build_headers;
 pub use headers::{HeaderMap, parse_headers};
 
@@ -53,8 +53,8 @@ use crate::{CowMailError, offset_in, parse_error};
 pub trait Header<'a>: Clone + Display {
     /// A new header from a key and a value.
     ///
-    /// The value is RFC 2047-encoded and folded as needed — see [`encode_header_value`] — so pass
-    /// it as the text it should decode to, not pre-encoded.
+    /// The value is RFC 2047-encoded and folded as needed, so pass it as the text it should decode
+    /// to, not pre-encoded.
     ///
     /// # Panics
     ///
@@ -211,8 +211,8 @@ pub trait Header<'a>: Clone + Display {
 }
 
 struct RFC2045HeaderValue<T> {
-    pub value: T,
-    pub params: BTreeMap<T, T>,
+    value: T,
+    params: BTreeMap<T, T>,
 }
 
 impl<T: ToString> Display for RFC2045HeaderValue<T> {
diff --git a/src/lib.rs b/src/lib.rs
index 1e92580..9593da9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -238,7 +238,7 @@ impl ContentType {
     ///
     /// `text/plain` normally, but `message/rfc822` for a part of a `multipart/digest`, per RFC
     /// 2046 section 5.1.5. Pass whether the part sits in such a digest.
-    pub fn default_conditional(in_multipart_digest: bool) -> Self {
+    pub(crate) fn default_conditional(in_multipart_digest: bool) -> Self {
         match in_multipart_digest {
             true => mime::MESSAGE_RFC822,
             false => mime::TEXT_PLAIN,
@@ -508,8 +508,8 @@ pub trait Mail<'a, T: Header<'a> + 'a>: HeaderMap<'a, T> {
 
     /// The content type to assume when the part has no `Content-Type` header.
     ///
-    /// Normally `text/plain; charset=us-ascii`, but `message/rfc822` inside a `multipart/digest`.
-    /// See [`ContentType::default_conditional`].
+    /// Normally `text/plain; charset=us-ascii`, but `message/rfc822` inside a `multipart/digest`,
+    /// per RFC 2046 section 5.1.5.
     fn default_ctype(&self) -> ContentType;
 
     /// The body exactly as it sits in the message, still transfer-encoded.
@@ -808,7 +808,7 @@ pub struct CowMail<'a, H: Header<'a>> {
     /// The content type to assume while this part has no `Content-Type` header.
     ///
     /// Set while parsing, since only then is it known whether the part sits in a
-    /// `multipart/digest`. See [`ContentType::default_conditional`].
+    /// `multipart/digest` — which makes it `message/rfc822` rather than `text/plain`.
     pub default_ctype: ContentType,
 }
 
diff --git a/src/tests.rs b/src/tests.rs
index 55db65f..71271e8 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -1,4 +1,5 @@
 //use std::io::{Read, Write};
+use crate::header::encode_header_value;
 use crate::{BodyType, CowHeader, CowMail, Header, HeaderMap, Mail, mime};
 
 fn serialize<'a>(mail: &'a CowMail<'a, CowHeader<'a>>) -> Vec<u8> {
@@ -1215,3 +1216,11 @@ fn test_make_mixed_is_case_insensitive() {
     assert_eq!(mail.subparts.len(), 1);
     assert_eq!(String::from_utf8_lossy(&serialize(&mail)), raw);
 }
+
+// Was a doc test on `encode_header_value` before it became crate-private.
+// A word of allowed bytes is written as it stands; the rest is RFC 2047-encoded.
+#[test]
+fn test_encode_header_value() {
+    assert_eq!(encode_header_value("Subject", "a test"), "a test");
+    assert_eq!(encode_header_value("Subject", "Grüße"), "=?utf-8?b?R3LDvMOfZQ==?=");
+}