fix: double a quote in a search term, as notmuch expects

SearchTerm::quote() escaped an embedded double quote with a backslash.
notmuch has no backslash escape inside a quoted term: it doubles the
quote, and a backslash-escaped one ENDS the term. Selected text holding
a quote therefore let the rest of the selection reach the query as
syntax. Measured on a throwaway index: under a `tag:nomatch and` scope,
the backslash form of `x " or tag:inbox or id:"` matched every message,
while the doubled form matched none.

quote() now doubles the quote and leaves a backslash alone, since
notmuch reads it literally. Truncation still runs first, so a cut
cannot split a doubled pair.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/src/searchterm.cpp b/src/searchterm.cpp
index 6bfb521..16936df 100644
--- a/src/searchterm.cpp
+++ b/src/searchterm.cpp
@@ -34,10 +34,13 @@ QString quote(const QString &value)
     if (cleaned.size() > kMaxValueLength)
         cleaned.truncate(kMaxValueLength);
 
-    // Backslashes first: escaping the quotes first would then escape the
-    // backslashes this step adds, doubling them.
-    cleaned.replace(QLatin1Char('\\'), QStringLiteral("\\\\"));
-    cleaned.replace(QLatin1Char('"'), QStringLiteral("\\\""));
+    // notmuch escapes a quote inside a quoted term by DOUBLING it and has no
+    // backslash escape at all. A backslash-escaped quote ENDS the term, so
+    // `subject:"x \" or tag:inbox or id:"` let a selection walk out of the
+    // query it was meant to narrow: measured matching every message under a
+    // `tag:nomatch and` scope, where the doubled form matched none. A
+    // backslash is literal to notmuch and is left as it is.
+    cleaned.replace(QLatin1Char('"'), QStringLiteral("\"\""));
 
     return QLatin1Char('"') + cleaned + QLatin1Char('"');
 }