Join variables by their delimiter in quoted expansion

This switches quoted expansion like "$foo" to use foo's delimiter instead of
space. The delimiter is space for normal variables and colonf or path variables.
Expansions like "$PATH" will now expand using ':'.

src/common.cpp

@@ -1898,7 +1898,18 @@ wcstring_list_t split_string(const wcstring &val, wchar_t sep) {
 }
 
 wcstring join_strings(const wcstring_list_t &vals, wchar_t sep) {
+    if (vals.empty()) return wcstring{};
+
+    // Reserve the size we will need.
+    // count-1 separators, plus the length of all strings.
+    size_t size = vals.size() - 1;
+    for (const wcstring &s : vals) {
+        size += s.size();
+    }
+
+    // Construct the string.
     wcstring result;
+    result.reserve(size);
     bool first = true;
     for (const wcstring &s : vals) {
         if (!first) {

src/env.cpp

@@ -1302,10 +1302,13 @@ int env_remove(const wcstring &key, int var_mode) {
 
 const wcstring_list_t &env_var_t::as_list() const { return vals; }
 
+wchar_t env_var_t::get_delimiter() const {
+    return is_pathvar() ? PATH_ARRAY_SEP : NONPATH_ARRAY_SEP;
+}
+
 /// Return a string representation of the var.
 wcstring env_var_t::as_string() const {
-    wchar_t sep = is_pathvar() ? PATH_ARRAY_SEP : NONPATH_ARRAY_SEP;
-    return join_strings(vals, sep);
+    return join_strings(vals, get_delimiter());
 }
 
 void env_var_t::to_list(wcstring_list_t &out) const {

src/env.h

@@ -101,6 +101,9 @@ class env_var_t {
     void to_list(wcstring_list_t &out) const;
     const wcstring_list_t &as_list() const;
 
+    /// \return the character used when delimiting quoted expansion.
+    wchar_t get_delimiter() const;
+
     void set_vals(wcstring_list_t v) { vals = std::move(v); }
 
     void set_exports(bool exportv) {

src/expand.cpp

@@ -447,6 +447,9 @@ static bool expand_variables(wcstring instr, std::vector<completion_t> *out, siz
     }
 
     if (is_single) {
+        // Quoted expansion. Here we expect the variable's delimiter.
+        // Note history always has a space delimiter.
+        wchar_t delimit = history ? L' ' : var->get_delimiter();
         wcstring res(instr, 0, varexp_char_idx);
         if (!res.empty()) {
             if (res.back() != VARIABLE_EXPAND_SINGLE) {
@@ -457,15 +460,8 @@ static bool expand_variables(wcstring instr, std::vector<completion_t> *out, siz
             }
         }
 
-        // Append all entries in var_item_list, separated by spaces.
-        // Remove the last space.
-        if (!var_item_list.empty()) {
-            for (const wcstring &item : var_item_list) {
-                res.append(item);
-                res.push_back(L' ');
-            }
-            res.pop_back();
-        }
+        // Append all entries in var_item_list, separated by the delimiter.
+        res.append(join_strings(var_item_list, delimit));
         res.append(instr, var_name_and_slice_stop, wcstring::npos);
         return expand_variables(std::move(res), out, varexp_char_idx, errors);
     } else {

tests/expansion.err

@@ -19,3 +19,6 @@ echo $$paren
 
 ####################
 # Test tilde expansion
+
+####################
+# Test delimiters

tests/expansion.in

@@ -126,3 +126,8 @@ end
 unlink $tmpdir/linkhome
 rmdir $tmpdir/realhome
 rmdir $tmpdir
+
+logmsg Test delimiters
+set TEST_DELIMITER one two three
+set TEST_DELIMITER_PATH one two three
+echo "$TEST_DELIMITER" "$TEST_DELIMITER_PATH"

tests/expansion.out

@@ -73,3 +73,7 @@ All digits: 0
 
 ####################
 # Test tilde expansion
+
+####################
+# Test delimiters
+one two three one:two:three

tests/test3.in

@@ -306,8 +306,9 @@ set -gx FOOPATH one two three four
 ../test/root/bin/fish -c 'echo Elements in FOO and FOOPATH: (count $FOO) (count $FOOPATH)'
 # some must use colon separators!
 set -lx MANPATH man1 man2 man3 ; env | grep '^MANPATH='
-# ensure we don't escape colon values
+# ensure we don't escape space and colon values
 set -x DONT_ESCAPE_COLONS 1: 2: :3: ; env | grep '^DONT_ESCAPE_COLONS='
-
+set -x DONT_ESCAPE_SPACES '1 ' '2 ' ' 3 ' 4 ; env | grep '^DONT_ESCAPE_SPACES='
+set -x DONT_ESCAPE_COLONS_PATH 1: 2: :3: ; env | grep '^DONT_ESCAPE_COLONS_PATH='
 
 true

tests/test3.out

@@ -44,3 +44,5 @@ Elements in DISPLAY: 1
 Elements in FOO and FOOPATH: 1 4
 MANPATH=man1:man2:man3
 DONT_ESCAPE_COLONS=1: 2: :3:
+DONT_ESCAPE_SPACES=1  2   3  4
+DONT_ESCAPE_COLONS_PATH=1::2:::3: