Enable multi-line edit when the line ends with a pipe (#1285)

src/reader.cpp

@@ -302,6 +302,7 @@ static volatile sig_atomic_t interrupted = 0;
 // Prototypes for a bunch of functions defined later on.
 static bool is_backslashed(const wcstring &str, size_t pos);
 static wchar_t unescaped_quote(const wcstring &str, size_t pos);
+static bool ends_with_pipe(const wcstring &str, size_t pos);
 
 /// Mode on startup, which we restore on exit.
 static struct termios terminal_mode_on_startup;
@@ -2302,6 +2303,19 @@ static bool is_backslashed(const wcstring &str, size_t pos) {
     return (count % 2) == 1;
 }
 
+/// Test if the specified string ends with pipe. Whitespaces at the end are ignored. It returns
+/// false if backslashed before the pipe because it should be treated as an escaped character.
+static bool ends_with_pipe(const wcstring &str, size_t pos) {
+    if (pos > str.size()) return false;
+
+    while (pos--) {
+        wchar_t c = str.at(pos);
+        if (c == L'|') return !is_backslashed(str, pos);
+        if (!iswspace(c)) break;
+    }
+    return false;
+}
+
 static wchar_t unescaped_quote(const wcstring &str, size_t pos) {
     wchar_t result = L'\0';
     if (pos < str.size()) {
@@ -2751,6 +2765,12 @@ const wchar_t *reader_readline(int nchars) {
                     insert_char(el, '\n');
                     break;
                 }
+                // A newline is inserted if the line ends with a pipe (issue #1285).
+                if (ends_with_pipe(el->text, el->size())) {
+                    el->position = el->size();
+                    insert_char(el, '\n');
+                    break;
+                }
 
                 // See if this command is valid.
                 int command_test_result = data->test_func(el->text.c_str());