gkeyfile: Fix parsing of new lines in comments

Previously, the code which parsed comments in key files would append a
line break to the comment where there was none before; this was part of
the code for handling re-inserting line breaks into multi-line comments
after removing the ‘#’ prefix. Now, we don’t add a terminal line break.

This was slightly icky to implement because parse_value_as_comment() is
called once for each line of a multi-line comment.

This expands the existing test case to cover a single line comment, and
also fixes the documentation to correctly state that the leading ‘#’
*is* removed and mention the new line break behaviour.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://gitlab.gnome.org/GNOME/glib/issues/107

glib/gkeyfile.c

@@ -599,7 +599,8 @@ static gboolean              g_key_file_parse_value_as_boolean (GKeyFile
 static gchar                *g_key_file_parse_boolean_as_value (GKeyFile               *key_file,
 								gboolean                value);
 static gchar                *g_key_file_parse_value_as_comment (GKeyFile               *key_file,
-                                                                const gchar            *value);
+                                                                const gchar            *value,
+                                                                gboolean                is_final_line);
 static gchar                *g_key_file_parse_comment_as_value (GKeyFile               *key_file,
                                                                 const gchar            *comment);
 static void                  g_key_file_parse_key_value_pair   (GKeyFile               *key_file,
@@ -3512,7 +3513,8 @@ g_key_file_get_key_comment (GKeyFile     *key_file,
       if (string == NULL)
 	string = g_string_sized_new (512);
 
-      comment = g_key_file_parse_value_as_comment (key_file, pair->value);
+      comment = g_key_file_parse_value_as_comment (key_file, pair->value,
+                                                   (tmp->prev == key_node));
       g_string_append (string, comment);
       g_free (comment);
       
@@ -3569,7 +3571,8 @@ get_group_comment (GKeyFile       *key_file,
       if (string == NULL)
         string = g_string_sized_new (512);
 
-      comment = g_key_file_parse_value_as_comment (key_file, pair->value);
+      comment = g_key_file_parse_value_as_comment (key_file, pair->value,
+                                                   (tmp->prev == NULL));
       g_string_append (string, comment);
       g_free (comment);
 
@@ -3640,7 +3643,9 @@ g_key_file_get_top_comment (GKeyFile  *key_file,
  * @group_name. If both @key and @group_name are %NULL, then
  * @comment will be read from above the first group in the file.
  *
- * Note that the returned string includes the '#' comment markers.
+ * Note that the returned string does not include the '#' comment markers,
+ * but does include any whitespace after them (on each line). It includes
+ * the line breaks between lines, but does not include the final line break.
  *
  * Returns: a comment that should be freed with g_free()
  *
@@ -4546,7 +4551,8 @@ g_key_file_parse_boolean_as_value (GKeyFile *key_file,
 
 static gchar *
 g_key_file_parse_value_as_comment (GKeyFile    *key_file,
-                                   const gchar *value)
+                                   const gchar *value,
+                                   gboolean     is_final_line)
 {
   GString *string;
   gchar **lines;
@@ -4558,13 +4564,22 @@ g_key_file_parse_value_as_comment (GKeyFile    *key_file,
 
   for (i = 0; lines[i] != NULL; i++)
     {
-        if (lines[i][0] != '#')
+      const gchar *line = lines[i];
-           g_string_append_printf (string, "%s\n", lines[i]);
+
-        else 
+      if (i != 0)
-           g_string_append_printf (string, "%s\n", lines[i] + 1);
+        g_string_append_c (string, '\n');
+
+      if (line[0] == '#')
+        line++;
+      g_string_append (string, line);
     }
   g_strfreev (lines);
 
+  /* This function gets called once per line of a comment, but we don’t want
+   * to add a trailing newline. */
+  if (!is_final_line)
+    g_string_append_c (string, '\n');
+
   return g_string_free (string, FALSE);
 }
 

glib/tests/keyfile.c

@@ -378,14 +378,16 @@ test_comments (void)
     "key2 = value2\n"
     "# line end check\r\n"
     "key3 = value3\n"
+    "# single line comment\n"
     "key4 = value4\n"
     "# group comment\n"
     "# group comment, continued\n"
     "[group2]\n";
 
-  const gchar *top_comment= " top comment\n top comment, continued\n";
+  const gchar *top_comment = " top comment\n top comment, continued";
-  const gchar *group_comment= " group comment\n group comment, continued\n";
+  const gchar *group_comment = " group comment\n group comment, continued";
-  const gchar *key_comment= " key comment\n key comment, continued\n";
+  const gchar *key_comment = " key comment\n key comment, continued";
+  const gchar *key4_comment = " single line comment";
 
   keyfile = load_data (data, 0);
 
@@ -436,6 +438,11 @@ test_comments (void)
   check_no_error (&error);
   g_assert (comment == NULL);
 
+  comment = g_key_file_get_comment (keyfile, "group1", "key4", &error);
+  check_no_error (&error);
+  check_name ("key comment", comment, key4_comment, 0);
+  g_free (comment);
+
   comment = g_key_file_get_comment (keyfile, "group2", NULL, &error);
   check_no_error (&error);
   check_name ("group comment", comment, group_comment, 0);