Rewrite and adopt print_help in Rust

CMakeLists.txt

@@ -198,12 +198,12 @@ fish_link_deps_and_sign(fish)
 
 # Define fish_indent.
 add_executable(fish_indent
-               src/fish_indent.cpp src/print_help.cpp)
+               src/fish_indent.cpp)
 fish_link_deps_and_sign(fish_indent)
 
 # Define fish_key_reader.
 add_executable(fish_key_reader
-               src/fish_key_reader.cpp src/print_help.cpp)
+               src/fish_key_reader.cpp)
 fish_link_deps_and_sign(fish_key_reader)
 
 # Set up the docs.

fish-rust/build.rs

@@ -58,6 +58,7 @@ fn main() {
         "src/parse_constants.rs",
         "src/parse_tree.rs",
         "src/parse_util.rs",
+        "src/print_help.rs",
         "src/redirection.rs",
         "src/signal.rs",
         "src/smoke.rs",

fish-rust/src/lib.rs

@@ -52,6 +52,7 @@ mod parse_tree;
 mod parse_util;
 mod parser_keywords;
 mod path;
+mod print_help;
 mod re;
 mod reader;
 mod redirection;

fish-rust/src/print_help.rs

@@ -0,0 +1,33 @@
+//! Helper for executables (not builtins) to print a help message
+//! Uses the fish in PATH, not necessarily the matching fish binary
+
+use libc::c_char;
+use std::ffi::{CStr, OsStr, OsString};
+use std::os::unix::ffi::OsStrExt;
+use std::process::Command;
+
+const HELP_ERR: &str = "Could not show help message";
+
+#[cxx::bridge]
+mod ffi2 {
+    extern "Rust" {
+        unsafe fn unsafe_print_help(command: *const c_char);
+    }
+}
+
+fn print_help(command: &OsStr) {
+    let mut cmdline = OsString::new();
+    cmdline.push("__fish_print_help ");
+    cmdline.push(command);
+
+    Command::new("fish")
+        .args([OsStr::new("-c"), &cmdline])
+        .spawn()
+        .expect(HELP_ERR);
+}
+
+unsafe fn unsafe_print_help(command_buf: *const c_char) {
+    let command_cstr: &CStr = unsafe { CStr::from_ptr(command_buf) };
+    let command = OsStr::from_bytes(command_cstr.to_bytes());
+    print_help(command);
+}

src/fish_indent.cpp

@@ -46,7 +46,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 #include "future_feature_flags.h"
 #include "highlight.h"
 #include "operation_context.h"
-#include "print_help.h"
+#include "print_help.rs.h"
 #include "tokenizer.h"
 #include "wcstringutil.h"
 #include "wutil.h"  // IWYU pragma: keep
@@ -341,7 +341,7 @@ int main(int argc, char *argv[]) {
                 break;
             }
             case 'h': {
-                print_help("fish_indent");
+                unsafe_print_help("fish_indent");
                 exit(0);
             }
             case 'v': {

src/fish_key_reader.cpp

@@ -30,7 +30,7 @@
 #include "input_common.h"
 #include "maybe.h"
 #include "parser.h"
-#include "print_help.h"
+#include "print_help.rs.h"
 #include "proc.h"
 #include "reader.h"
 #include "signals.h"
@@ -312,7 +312,7 @@ static bool parse_flags(int argc, char **argv, bool *continuous_mode, bool *verb
                 break;
             }
             case 'h': {
-                print_help("fish_key_reader");
+                unsafe_print_help("fish_key_reader");
                 exit(0);
             }
             case 'v': {

src/print_help.cpp

@@ -1,24 +0,0 @@
-// Print help message for the specified command.
-#include "config.h"  // IWYU pragma: keep
-
-#include "print_help.h"
-
-#include <stdio.h>
-#include <stdlib.h>
-
-#include <cstring>
-
-#include "common.h"
-
-#define CMD_LEN 1024
-
-#define HELP_ERR "Could not show help message\n"
-
-void print_help(const char *c) {
-    char cmd[CMD_LEN];
-    int printed = snprintf(cmd, CMD_LEN, "fish -c '__fish_print_help %s'", c);
-
-    if (printed < CMD_LEN && system(cmd) == -1) {
-        write_loop(2, HELP_ERR, std::strlen(HELP_ERR));
-    }
-}

src/print_help.h

@@ -1,8 +0,0 @@
-// Print help message for the specified command.
-#ifndef FISH_PRINT_HELP_H
-#define FISH_PRINT_HELP_H
-
-/// Print help message for the specified command.
-void print_help(const char *cmd);
-
-#endif