Escape separators (colon and equals) to improve completion

Fish completes parts of words split by the separators, so things like
`dd if=/dev/sd<TAB>` work.
This commit improves interactive completion if completion strings legitimately
contain '=' or ':'.  Consider this example where completion will suggest
a🅰️1 and other files in the cwd in addition to a:1

touch a:1; complete -C'ls a:'

This behavior remains unchanged, but this commit allows to quote or escape
separators, so that e.g. `ls "a:<TAB>` and `ls a\:<TAB>` successfully complete
the filename.

This also makes the completion insert those escapes automatically unless
already quoted.
So `ls a<TAB>` will give `ls a\:1`.

Both changes match bash's behavior.

src/common.cpp

@@ -999,6 +999,7 @@ static void escape_string_script(const wchar_t *orig_in, size_t in_len, wcstring
     const bool escape_all = static_cast<bool>(flags & ESCAPE_ALL);
     const bool no_quoted = static_cast<bool>(flags & ESCAPE_NO_QUOTED);
     const bool no_tilde = static_cast<bool>(flags & ESCAPE_NO_TILDE);
+    const bool escape_separators = static_cast<bool>(flags & ESCAPE_SEPARATORS);
     const bool no_caret = feature_test(features_t::stderr_nocaret);
     const bool no_qmark = feature_test(features_t::qmark_noglob);
 
@@ -1098,9 +1099,12 @@ static void escape_string_script(const wchar_t *orig_in, size_t in_len, wcstring
                 case L';':
                 case L'"':
                 case L'%':
-                case L'~': {
+                case L'~':
+                case L':':
+                case L'=': {
                     bool char_is_normal = (c == L'~' && no_tilde) || (c == L'^' && no_caret) ||
-                                          (c == L'?' && no_qmark);
+                                          (c == L'?' && no_qmark) ||
+                                          ((c == L':' || c == L'=') && !escape_separators);
                     if (!char_is_normal) {
                         need_escape = 1;
                         if (escape_all) out += L'\\';

src/common.h

@@ -134,7 +134,9 @@ enum {
     /// string.
     ESCAPE_NO_QUOTED = 1 << 1,
     /// Do not escape tildes.
-    ESCAPE_NO_TILDE = 1 << 2
+    ESCAPE_NO_TILDE = 1 << 2,
+    /// Escape colon and equal sign.
+    ESCAPE_SEPARATORS = 1 << 3,
 };
 typedef unsigned int escape_flags_t;
 

src/complete.cpp

@@ -1098,6 +1098,7 @@ void completer_t::complete_param_expand(const wcstring &str, bool do_file,
     // Squelch file descriptions per issue #254.
     if (this->type() == COMPLETE_AUTOSUGGEST || do_file) flags |= expand_flag::no_descriptions;
 
+    // Expand words separated by '=' separately, unless '=' is escaped or quoted.
     // We have the following cases:
     //
     // --foo=bar => expand just bar
@@ -1105,14 +1106,16 @@ void completer_t::complete_param_expand(const wcstring &str, bool do_file,
     // foo=bar => expand the whole thing, and also just bar
     //
     // We also support colon separator (#2178). If there's more than one, prefer the last one.
-    size_t sep_index = str.find_last_of(L"=:");
-    bool complete_from_separator = (sep_index != wcstring::npos);
+    size_t sep_index = str.size();
+    do {
+        sep_index = sep_index == 0 ? wcstring::npos : str.find_last_of(L"=:", sep_index - 1);
+    } while (sep_index != wcstring::npos && is_backslashed(str, sep_index));
+    wchar_t quote = L'\0';
+    parse_util_get_parameter_info(str, str.size(), &quote, NULL, NULL);
+    bool complete_from_separator = (quote == L'\0') && (sep_index != wcstring::npos);
     bool complete_from_start = !complete_from_separator || !string_prefixes_string(L"-", str);
 
     if (complete_from_separator) {
-        // FIXME: This just cuts the token,
-        // so any quoting or braces gets lost.
-        // See #4954.
         const wcstring sep_string = wcstring(str, sep_index + 1);
         std::vector<completion_t> local_completions;
         if (expand_string(sep_string, &local_completions, flags, vars, parser, NULL) ==

src/parse_util.cpp

@@ -523,7 +523,8 @@ void parse_util_get_parameter_info(const wcstring &cmd, const size_t pos, wchar_
 wcstring parse_util_escape_string_with_quote(const wcstring &cmd, wchar_t quote, bool no_tilde) {
     wcstring result;
     if (quote == L'\0') {
-        escape_flags_t flags = ESCAPE_ALL | ESCAPE_NO_QUOTED | (no_tilde ? ESCAPE_NO_TILDE : 0);
+        escape_flags_t flags =
+            ESCAPE_ALL | ESCAPE_NO_QUOTED | (no_tilde ? ESCAPE_NO_TILDE : 0) | ESCAPE_SEPARATORS;
         result = escape_string(cmd, flags);
     } else {
         // Here we are going to escape a string with quotes.

src/reader.cpp

@@ -488,7 +488,6 @@ class reader_data_t : public std::enable_shared_from_this<reader_data_t> {
 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);
 
 /// Mode on startup, which we restore on exit.
@@ -2297,9 +2296,7 @@ static int can_read(int fd) {
     return select(fd + 1, &fds, 0, 0, &can_read_timeout) == 1;
 }
 
-/// Test if the specified character in the specified string is backslashed. pos may be at the end of
-/// the string, which indicates if there is a trailing backslash.
-static bool is_backslashed(const wcstring &str, size_t pos) {
+bool is_backslashed(const wcstring &str, size_t pos) {
     // note pos == str.size() is OK.
     if (pos > str.size()) return false;
 

src/reader.h

@@ -232,4 +232,8 @@ void reader_bg_job_warning(const parser_t &parser);
 /// been executed between invocations of code.
 uint64_t reader_run_count();
 
+/// Test if the specified character in the specified string is backslashed. pos may be at the end of
+/// the string, which indicates if there is a trailing backslash.
+bool is_backslashed(const wcstring &str, size_t pos);
+
 #endif