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fix(gmail): pre-wrap quoted lines to prevent QP soft-wrap corruption in +reply #833

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fix(gmail): pre-wrap quoted lines to prevent QP soft-wrap corruption in +reply #833

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5 changes: 5 additions & 0 deletions .changeset/fix-769-reply-qp-soft-wrap.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@googleworkspace/cli": patch
---

fix(gmail): pre-wrap quoted lines to prevent QP soft-wrap corruption in +reply
73 changes: 73 additions & 0 deletions crates/google-workspace-cli/src/helpers/gmail/reply.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -371,10 +371,35 @@ fn create_reply_raw_message(
finalize_message(mb, body, envelope.html, attachments)
}

fn wrap_line(line: &str, max_len: usize) -> Vec<String> {
if line.len() <= max_len {
return vec![line.to_string()];
}
// word-wrap at max_len, breaking on spaces
let mut result = Vec::new();
let mut current = String::new();
for word in line.split(' ') {
if current.is_empty() {
current.push_str(word);
} else if current.len() + 1 + word.len() <= max_len {
current.push(' ');
current.push_str(word);
} else {
result.push(current.clone());
current = word.to_string();
}
}
if !current.is_empty() {
result.push(current);
}
result
}
Comment on lines +374 to +396
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@gemini-code-assist gemini-code-assist Bot Jun 2, 2026

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high

The current implementation of wrap_line does not wrap individual words that are longer than max_len. If an email contains a long unbroken string (such as a URL, a base64 block, or a long path), line.split(' ') will produce a single word exceeding max_len. Since the function does not split words longer than max_len, the line will remain unwrapped and will still exceed the SMTP/MIME 76-character limit once prefixed with > . This will trigger the exact Quoted-Printable soft-wrap corruption this PR aims to prevent.

To fix this, we should hard-wrap words longer than max_len at safe UTF-8 character boundaries.

fn wrap_line(line: &str, max_len: usize) -> Vec<String> {
    if line.len() <= max_len {
        return vec![line.to_string()];
    }
    let mut result = Vec::new();
    let mut current = String::new();
    for word in line.split(' ') {
        if word.len() > max_len {
            if !current.is_empty() {
                result.push(current.clone());
                current.clear();
            }
            let mut start = 0;
            while start < word.len() {
                let mut end = start + max_len;
                if end >= word.len() {
                    current = word[start..].to_string();
                    break;
                }
                while !word.is_char_boundary(end) {
                    end -= 1;
                }
                if end == start {
                    end = start + 1;
                    while end < word.len() && !word.is_char_boundary(end) {
                        end += 1;
                    }
                }
                result.push(word[start..end].to_string());
                start = end;
            }
        } else {
            if current.is_empty() {
                current.push_str(word);
            } else if current.len() + 1 + word.len() <= max_len {
                current.push(' ');
                current.push_str(word);
            } else {
                result.push(current.clone());
                current = word.to_string();
            }
        }
    }
    if !current.is_empty() {
        result.push(current);
    }
    result
}
References
  1. Avoid introducing changes that are outside the primary goal of a pull request to prevent scope creep.


fn format_quoted_original(original: &OriginalMessage) -> String {
let quoted_body: String = original
.body_text
.lines()
.flat_map(|line| wrap_line(line, 73))
.map(|line| format!("> {}", line))
.collect::<Vec<_>>()
.join("\r\n");
Expand Down Expand Up @@ -1300,6 +1325,54 @@ mod tests {
assert!(quoted.contains("> Hello"));
}

#[test]
fn test_format_quoted_original_long_lines_do_not_exceed_75_chars() {
// Lines near 70–75 chars would exceed 76 chars after "> " prefix without pre-wrapping.
let long_line = "This is a fairly long line of text that sits right around seventy-four characters.";
assert!(long_line.len() > 73);
let original = OriginalMessage {
from: Mailbox::parse("alice@example.com"),
date: Some("Mon, 1 Jan 2026 00:00:00 +0000".to_string()),
body_text: long_line.to_string(),
..Default::default()
};
let quoted = format_quoted_original(&original);
for line in quoted.lines() {
assert!(
line.len() <= 76,
"Line exceeds 76 chars ({} chars): {:?}",
line.len(),
line
);
}
}

#[test]
fn test_word_wrap_preserves_short_lines() {
let short = "Hello, world!";
let wrapped = wrap_line(short, 73);
assert_eq!(wrapped, vec!["Hello, world!"]);
}

#[test]
fn test_word_wrap_breaks_long_line() {
// Build a line that is >73 chars
let line = "word1 word2 word3 word4 word5 word6 word7 word8 word9 word10 word11 word12 word13";
assert!(line.len() > 73);
let wrapped = wrap_line(line, 73);
assert!(wrapped.len() > 1, "Long line should be split into multiple chunks");
for chunk in &wrapped {
assert!(
chunk.len() <= 73,
"Chunk exceeds 73 chars ({} chars): {:?}",
chunk.len(),
chunk
);
}
// Reassembling should recover the original
assert_eq!(wrapped.join(" "), line);
}

// --- end-to-end --to behavioral tests ---

#[test]
Expand Down
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