fix: fix formatting of whitespace-only values

Cargo.toml

@@ -22,7 +22,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.34.1-alpha.2"
+version = "0.34.1-alpha.3"
 edition = "2024"
 repository = "https://github.com/pamburus/hl"
 license = "MIT"

src/formatting.rs

@@ -1,6 +1,9 @@
 // std imports
 use std::sync::Arc;
 
+// third-party imports
+use enumset::{EnumSet, EnumSetType};
+
 // workspace imports
 use encstr::EncodedString;
 
@@ -745,29 +748,37 @@ impl<'a> FieldFormatter<'a> {
 
 // ---
 
-pub trait WithAutoTrim {
-    fn with_auto_trim<F, R>(&mut self, f: F) -> R
+trait WithAutoTrim {
+    fn with_auto_trim<F, R>(&mut self, f: F, flags: impl Into<AutoTrimFlags>) -> R
     where
         F: FnOnce(&mut Self) -> R;
 }
 
 impl WithAutoTrim for Vec<u8> {
     #[inline(always)]
-    fn with_auto_trim<F, R>(&mut self, f: F) -> R
+    fn with_auto_trim<F, R>(&mut self, f: F, flags: impl Into<AutoTrimFlags>) -> R
     where
         F: FnOnce(&mut Self) -> R,
     {
+        let flags = flags.into();
         let begin = self.len();
         let result = f(self);
         if let Some(end) = self[begin..].iter().rposition(|&b| !b.is_ascii_whitespace()) {
             self.truncate(begin + end + 1);
-        } else {
+        } else if !flags.contains(AutoTrimFlag::PreserveWhiteSpaceOnly) {
             self.truncate(begin);
         }
         result
     }
 }
 
+#[derive(EnumSetType, Debug)]
+enum AutoTrimFlag {
+    PreserveWhiteSpaceOnly,
+}
+
+type AutoTrimFlags = EnumSet<AutoTrimFlag>;
+
 // ---
 
 trait KeyPrettify {
@@ -810,7 +821,7 @@ pub mod string {
 
     // local imports
     use crate::{
-        formatting::WithAutoTrim,
+        formatting::{AutoTrimFlag, AutoTrimFlags, WithAutoTrim},
         model::{MAX_NUMBER_LEN, looks_like_number},
         settings::MessageFormat,
     };
@@ -907,7 +918,10 @@ pub mod string {
             }
 
             let begin = buf.len();
-            buf.with_auto_trim(|buf| ValueFormatRaw.format(input, buf))?;
+            buf.with_auto_trim(
+                |buf| ValueFormatRaw.format(input, buf),
+                AutoTrimFlag::PreserveWhiteSpaceOnly,
+            )?;
 
             let mut mask = Mask::empty();
 
@@ -952,7 +966,9 @@ pub mod string {
                 return Ok(());
             }
 
-            if !mask.intersects(Flag::Backtick | Flag::Control) {
+            const WS: Mask = mask!(Flag::NewLine | Flag::Tab | Flag::Space);
+
+            if !mask.intersects(Flag::Backtick | Flag::Control) && mask.intersects(!WS) {
                 buf.push(b'`');
                 buf.push(b'`');
                 buf[begin..].rotate_right(1);
@@ -998,7 +1014,7 @@ pub mod string {
             }
 
             let begin = buf.len();
-            buf.with_auto_trim(|buf| MessageFormatRaw.format(input, buf))?;
+            buf.with_auto_trim(|buf| MessageFormatRaw.format(input, buf), AutoTrimFlags::empty())?;
 
             let mut mask = Mask::empty();
 
@@ -1051,7 +1067,7 @@ pub mod string {
 
             let begin = buf.len();
             buf.push(b'"');
-            buf.with_auto_trim(|buf| MessageFormatRaw.format(input, buf))?;
+            buf.with_auto_trim(|buf| MessageFormatRaw.format(input, buf), AutoTrimFlags::empty())?;
 
             let mut mask = Mask::empty();
 
@@ -1100,7 +1116,7 @@ pub mod string {
             }
 
             let begin = buf.len();
-            buf.with_auto_trim(|buf| MessageFormatRaw.format(input, buf))?;
+            buf.with_auto_trim(|buf| MessageFormatRaw.format(input, buf), AutoTrimFlags::empty())?;
 
             let mut mask = Mask::empty();
 

src/formatting/tests.rs

@@ -1178,9 +1178,9 @@ mod string {
     #[case::trailing_newline("hello\n", "hello")]
     #[case::trailing_crlf("hello\r\n", "hello")]
     #[case::multiple_trailing("text   \t\n", "text")]
-    // Only whitespace after trimming still produces output, just empty after trim
-    #[case::only_spaces("   ", "")]
-    #[case::only_tabs("\t\t", "")]
+    // Only whitespace requires quoting
+    #[case::only_spaces("   ", r#""   ""#)]
+    #[case::only_tabs("\t\t", r#""\t\t""#)]
     // Leading whitespace is preserved and triggers quoting
     #[case::leading_space(" hello", r#"" hello""#)]
     // Leading tab uses backticks
@@ -1205,7 +1205,21 @@ mod string {
     }
 
     // ---
-    // Test 8: ValueFormatAuto special characters and edge cases
+    // Test 8: ValueFormatAuto error handling
+    // ---
+
+    #[test]
+    fn test_value_format_auto_invalid_json() {
+        use encstr::json::JsonEncodedString;
+
+        let invalid_json = JsonEncodedString::new(r#""invalid\xZZ""#);
+        let mut buf = Vec::new();
+        let result = ValueFormatAuto.format(EncodedString::Json(invalid_json), &mut buf);
+        assert!(result.is_err());
+    }
+
+    // ---
+    // Test 9: ValueFormatAuto special characters and edge cases
     // ---
 
     #[rstest]
@@ -1593,7 +1607,7 @@ mod string {
     #[case::trailing_space("message ", " | ", "message | ")]
     #[case::trailing_tab("message\t", " | ", "message | ")]
     #[case::trailing_newline("message\n", " | ", "message | ")]
-    // Whitespace-only: empty check is on input (before trim), so delimiter is appended
+    // Whitespace-only: trimmed to empty, so only delimiter appears
     #[case::only_spaces("   ", " | ", " | ")]
     fn test_message_format_delimited_whitespace(#[case] input: &str, #[case] delim: &str, #[case] expected: &str) {
         let formatter = MessageFormatDelimited::new(delim.to_string());