Treat comments ending in backslashes as not continuing onto the next line

Fixes #1255

3 files changed, 34 insertions, 2 deletions

diff --git a/reader.cpp b/reader.cpp
index 2700da0f..516a099e 100644
--- a/reader.cpp
+++ b/reader.cpp
@@ -3065,6 +3065,18 @@ static wchar_t unescaped_quote(const wcstring &str, size_t pos)
     return result;
 }
 
+/* Returns true if the last token is a comment. */
+static bool text_ends_in_comment(const wcstring &text)
+{
+    token_type last_type = TOK_NONE;
+    tokenizer_t tok(text.c_str(), TOK_ACCEPT_UNFINISHED | TOK_SHOW_COMMENTS | TOK_SQUASH_ERRORS);
+    while (tok_has_next(&tok))
+    {
+        last_type = tok_last_type(&tok);
+        tok_next(&tok);
+    }
+    return last_type == TOK_COMMENT;
+}
 
 const wchar_t *reader_readline(int nchars)
 {
@@ -3561,10 +3573,19 @@ const wchar_t *reader_readline(int nchars)
                 /* We only execute the command line */
                 editable_line_t *el = &data->command_line;
 
-                /* Allow backslash-escaped newlines, but only if the following character is whitespace, or we're at the end of the text (see issue #613) */
+                /* Allow backslash-escaped newlines, but only if the following character is whitespace, or we're at the end of the text (see issue #613) and not in a comment (#1255). */
                 if (is_backslashed(el->text, el->position))
                 {
-                    if (el->position >= el->size() || iswspace(el->text.at(el->position)))
+                    bool continue_on_next_line = false;
+                    if (el->position >= el->size())
+                    {
+                        continue_on_next_line = ! text_ends_in_comment(el->text);
+                    }
+                    else
+                    {
+                        continue_on_next_line = iswspace(el->text.at(el->position));
+                    }
+                    if (continue_on_next_line)
                     {
                         insert_char(el, '\n');
                         break;
diff --git a/tests/generic.expect b/tests/generic.expect
index 7a5b6407..33d260a7 100644
--- a/tests/generic.expect
+++ b/tests/generic.expect
@@ -33,3 +33,9 @@ send_line $hist_command
 expect_prompt -re {echo .history.*} {} unmatched {
     puts stderr "Couldn't find expected output $hist_command"
 }
+
+# Backslashes at end of comments (#1255)
+# This backslash should NOT cause the line to continue
+send_line "echo -n #comment\\"
+expect_prompt
+
diff --git a/tests/test1.in b/tests/test1.in
index b9db902a..cfea247a 100644
--- a/tests/test1.in
+++ b/tests/test1.in
@@ -155,6 +155,11 @@ echo before comment \
   # comment
   after comment
 
+# Backslashes are part of comments and do not join lines (#1255)
+# This should execute false, not echo it
+echo -n # comment\
+false
+
 function always_fails
     if true
         return 1