Proper handling of std.getopt.GetOptException - command-line

Question

What is the proper handling of the std.getopt.GetOptException Exception that is thrown when a required command line argument is missing.
Declaring an argument being required throws the following error which is way too verbose:
std.getopt.GetOptException#/Library/D/dmd/src/phobos/std/getopt.d(755): Required option file|f was not supplied
----------------
/Library/D/dmd/src/phobos/std/format.d-mixin-1127:1138 #safe std.getopt.GetoptResult std.getopt.getopt!(std.getopt.config, immutable(char)[], immutable(char)[], immutable(char)[]*, std.getopt.config, immutable(char)[], immutable(char)[], immutable(char)[]*, immutable(char)[], immutable(char)[], bool*, immutable(char)[], immutable(char)[], bool*).getopt(ref immutable(char)[][], std.getopt.config, immutable(char)[], immutable(char)[], immutable(char)[]*, std.getopt.config, immutable(char)[], immutable(char)[], immutable(char)[]*, immutable(char)[], immutable(char)[], bool*, immutable(char)[], immutable(char)[], bool*) [0xbb5a9d1]
source/app.d:11 _Dmain [0xbb58996]
std.getopt.GetOptException#/Library/D/dmd/src/phobos/std/getopt.d(755): Required option key|k was not supplied
Use the following code to reproduce it:
import std.stdio;
import std.getopt;
int main(string[] args)
{
string key;
string inputFile;
bool encrypt;
bool decrypt;
auto result = getopt(
args,
std.getopt.config.required,
"key|k", "The key to use", &key,
std.getopt.config.required,
"file|f", "The file to encrypt/decrypt", &inputFile,
"encrypt|e", "Encrypt the file", &encrypt,
"decrypt|d", "Decrypt the file", &decrypt
);
if (result.helpWanted) {
defaultGetoptPrinter("Some information about the program.", result.options);
}
return 0;
}

Answer 1

A reasonable way to do this is to wrap the getopt call in a try-catch block, catch any error, and write only the error message part before exiting. This will avoid the writing the stack trace, which is not helpful to most users. Modifying the above example:
import std.stdio;
import std.getopt;
int main(string[] args)
{
string key;
string inputFile;
bool encrypt;
bool decrypt;
try {
auto result = getopt(
args,
std.getopt.config.required,
"key|k", "The key to use", &key,
std.getopt.config.required,
"file|f", "The file to encrypt/decrypt", &inputFile,
"encrypt|e", "Encrypt the file", &encrypt,
"decrypt|d", "Decrypt the file", &decrypt
);
if (result.helpWanted) {
defaultGetoptPrinter("Some information about the program.", result.options);
}
}
catch (Exception e) {
stderr.writefln("Error processing command line arguments: %s", e.msg);
return 1;
}
return 0;
}
The error message when run:
Error processing command line arguments: Required option file|f was not supplied
There's a thread on the D language 'Learn' forum related to this that might be useful: What's the proper way to use std.getopt?. I've written some open source command line tools that are a bit more extensive examples, eg. tsv-sample.d.