fish_indent: Add a "--check" option to only test indentation

Fixes #7251.

doc_src/cmds/fish_indent.rst

@@ -22,6 +22,8 @@ The following options are available:
 
 - ``-i`` or ``--no-indent`` do not indent commands; only reformat to one job per line.
 
+- ``-c`` or ``--check`` do not indent, only return 0 if the code is already indented as fish_indent would, 1 otherwise.
+
 - ``-v`` or ``--version`` displays the current fish version and then exits.
 
 - ``--ansi`` colorizes the output using ANSI escape sequences, appropriate for the current $TERM, using the colors defined in the environment (such as ``$fish_color_command``).

src/fish_indent.cpp

@@ -836,12 +836,13 @@ int main(int argc, char *argv[]) {
         output_type_file,
         output_type_ansi,
         output_type_pygments_csv,
+        output_type_check,
         output_type_html
     } output_type = output_type_plain_text;
     const char *output_location = "";
     bool do_indent = true;
 
-    const char *short_opts = "+d:hvwiD:";
+    const char *short_opts = "+d:hvwicD:";
     const struct option long_opts[] = {{"debug-level", required_argument, nullptr, 'd'},
                                        {"debug-stack-frames", required_argument, nullptr, 'D'},
                                        {"dump-parse-tree", no_argument, nullptr, 'P'},
@@ -852,6 +853,7 @@ int main(int argc, char *argv[]) {
                                        {"html", no_argument, nullptr, 1},
                                        {"ansi", no_argument, nullptr, 2},
                                        {"pygments", no_argument, nullptr, 3},
+                                       {"check", no_argument, nullptr, 'c'},
                                        {nullptr, 0, nullptr, 0}};
 
     int opt;
@@ -889,6 +891,10 @@ int main(int argc, char *argv[]) {
                 output_type = output_type_pygments_csv;
                 break;
             }
+            case 'c': {
+                output_type = output_type_check;
+                break;
+            }
             case 'd': {
                 char *end;
                 long tmp;
@@ -997,6 +1003,12 @@ int main(int argc, char *argv[]) {
             case output_type_pygments_csv: {
                 DIE("pygments_csv should have been handled above");
             }
+            case output_type_check: {
+                if (output_wtext != src) {
+                    return 1;
+                }
+                break;
+            }
         }
 
         std::fputws(str2wcstring(colored_output).c_str(), stdout);

tests/checks/indent.fish

@@ -318,3 +318,10 @@ command 2' | $fish_indent
 #CHECK: {{^}}command 1 |
 #CHECK: {{^    }}command 1 cont ||
 #CHECK: {{^}}command 2
+
+echo " foo" | fish_indent --check
+echo $status
+#CHECK: 1
+echo "foo" | fish_indent --check
+echo $status
+#CHECK: 0