improve error message system

Move away from the exception-based system where we throw an Exception
to stop the program (which is caught by main) and use a new die
function that accesses args[0], prints an error and stops the program.
Users should not notice a difference, I think this system is more
lightweight and requires less code.

esv.d

@@ -20,15 +20,13 @@
 
 module esv;
 
+import std.algorithm : startsWith;
 import std.conv    : to, ConvException;
-import std.exception : enforce;
 import std.file    : exists, mkdirRecurse, write, FileException;
 import std.format  : format;
 import std.getopt  : getopt, GetOptException;
-import std.getopt  : getoptConfig = config;
 import std.path    : baseName, dirName, expandTilde, isValidPath;
 import std.process : environment, executeShell;
-import std.regex   : regex, matchFirst, replaceAll, replaceFirst;
 import std.stdio   : writef, writeln, writefln, File;
 import std.string  : splitLines;
 
@@ -51,6 +49,7 @@ bool   rFlag, RFlag; /* passage references */
 string sFlag;        /* search passages */
 bool   VFlag;        /* show version */
 
+string[] mainArgs;
 File stderr;
 
 version (OpenBSD) {
@@ -59,55 +58,31 @@ version (OpenBSD) {
 
 int
 main(string[] args)
-{
-	bool success;
-
-	/* @safe way of opening stderr on Unix */
-	stderr = File("/dev/stderr", "w");
-
-	version (OpenBSD) {
-		import core.sys.openbsd.unistd : pledge;
-		import std.string : toStringz;
-
-		promises = toStringz("stdio rpath wpath cpath inet dns proc exec prot_exec");
-		pledge(promises, null);
-	}
-
-	debug {
-		return run(args) ? 0 : 1;
-	}
-
-	try {
-		success = run(args);
-	} catch (Exception e) {
-		if (typeid(e) == typeid(Exception)) {
-			stderr.writefln("%s: %s", args[0].baseName(), e.msg);
-		} else {
-			stderr.writefln("%s: uncaught %s in %s:%d: %s",
-				args[0].baseName(),
-				typeid(e).name,
-				e.file, e.line, e.msg);
-			stderr.writefln("this is probably a bug; it would be greatly appreciated if you reported it at:\n\n  %s",
-				BUGREPORTURL);
-		}
-	}
-
-	return success ? 0 : 1;
-}
-
-bool
-run(string[] args)
 {
 	string apiKey;
 	string configPath;
 	INIUnit ini;
 	ESVApi esv;
 
+	mainArgs = args;
+
+	version (OpenBSD) () @trusted {
+		import core.sys.openbsd.unistd : pledge;
+		import std.string : toStringz;
+
+		promises = toStringz("stdio rpath wpath cpath inet dns proc exec prot_exec");
+		pledge(promises, null);
+	}();
+
+	/* @safe way of opening stderr on Unix */
+	stderr = File("/dev/stderr", "w");
+
 	/* Parse command-line options */
 	try {
+		import std.getopt : cfg = config;
 		getopt(args,
-			getoptConfig.bundling,
+			cfg.bundling,
-			getoptConfig.caseSensitive,
+			cfg.caseSensitive,
 			"a", &aFlag,
 			"C", &CFlag,
 			"F", &FFlag, "f", &fFlag,
@@ -119,20 +94,19 @@ run(string[] args)
 			"V", &VFlag,
 		);
 	} catch (GetOptException e) {
-		enforce(e.msg.matchFirst(regex("^Unrecognized option")).empty,
+		enforceDie(!e.msg.startsWith("Unrecognized option"),
 			"unknown option " ~ e.extractOpt());
-		enforce(e.msg.matchFirst(regex("^Missing value for argument")).empty,
+		enforceDie(!e.msg.startsWith("Missing value for argument"),
 			"missing argument for option " ~ e.extractOpt());
 
-		throw new Exception(e.msg); /* catch-all */
+		die(e.msg); /* catch-all */
 	} catch (ConvException e) {
-		throw new Exception(
+		die("illegal argument to -l option -- must be integer");
-			"illegal argument to -l option -- must be integer");
 	}
 
 	if (VFlag) {
 		writeln("esv version " ~ VERSION);
-		return true;
+		return 0;
 	}
 
 	if (sFlag != "") {
@@ -142,26 +116,25 @@ run(string[] args)
 
 	if (args.length < 3) {
 		stderr.writefln("usage: %s [-aFfHhNnRrV] [-C config] [-l length] [-s query] book verses", args[0].baseName());
-		return false;
+		return 1;
 	}
 
-	enforce(bookValid(args[1].parseBook()),
+	enforceDie(bookValid(args[1].parseBook()),
-		format!"book '%s' does not exist"(args[1]));
+		"book '%s' does not exist", args[1]);
-	enforce(verseValid(args[2]),
+	enforceDie(verseValid(args[2]),
-		format!"invalid verse format '%s'"(args[2]));
+		"invalid verse format '%s'", args[2]);
 
 	/* determine configuration file
 	 * Options have first priority, then environment variables,
 	 * then the default path */
 config:
-	configPath = environment.get(ENV_CONFIG, DEFAULT_CONFIGPATH)
+	configPath = environment.get(ENV_CONFIG, DEFAULT_CONFIGPATH).expandTilde();
-		.expandTilde();
 	try {
 		if (CFlag != "") { /* if -C was given */
-			enforce(isValidPath(CFlag), CFlag ~ ": invalid path");
+			enforceDie(isValidPath(CFlag), CFlag ~ ": invalid path");
 			configPath = CFlag.expandTilde();
 		} else {
-			enforce(isValidPath(configPath),
+			enforceDie(isValidPath(configPath),
 				configPath ~ ": invalid path");
 
 			if (!configPath.exists()) {
@@ -176,8 +149,8 @@ key = %s
 # custom API parameters using `parameters`:
 #parameters = &my-parameter=value
 
-# Some other settings that modify how the passages are displayed:
+# Settings that modify how passages are displayed:
-#[passage]
+[passage]
 #footnotes = false
 #headings = false
 #passage-references = false
@@ -188,16 +161,17 @@ key = %s
 		readINIFile(ini, configPath);
 	} catch (FileException e) {
 		/* filesystem syscall errors */
-		throw new Exception(e.msg);
+		die(e.msg);
 	}
 
+	enforceDie(!(aFlag && sFlag), "cannot specify both -a and -s flags");
+
 	apiKey = ini["api"].key("key");
-	enforce(apiKey != null,
+	enforceDie(apiKey != null,
 		"API key not present in configuration file; cannot proceed");
 
 	esv = new ESVApi(apiKey);
 
-	enforce(!(aFlag && sFlag), "cannot specify both -a and -s options");
 	if (aFlag) {
 		string tmpf, mpegPlayer;
 
@@ -205,12 +179,11 @@ key = %s
 		mpegPlayer = environment.get(ENV_PLAYER, DEFAULT_MPEGPLAYER);
 
 		/* check for an audio player */
-		enforce(
+		enforceDie(
 			executeShell(
 				format!"command -v %s >/dev/null 2>&1"(mpegPlayer)
 			).status == 0,
-			format!"%s is required for audio mode; cannot continue"(mpegPlayer)
+			mpegPlayer ~ " is required for audio mode; cannot continue");
-		);
 
 		/* esv has built-in support for mpg123 and mpv.
 		 * other players will work, just recompile with
@@ -219,32 +192,37 @@ key = %s
 		mpegPlayer ~=
 			mpegPlayer == "mpg123" ? " -q " :
 			mpegPlayer == "mpv"    ? " --msg-level=all=no " : " ";
-		/* spawn mpg123 */
+		/* spawn the player */
 		executeShell(mpegPlayer ~ tmpf);
-		return true;
+		return 0;
 	}
+
 	if (sFlag) {
 		writeln(esv.searchFormat(sFlag));
-		return true;
+		return 0;
 	}
 
 	esv.extraParameters = ini["api"].key("parameters", "");
 
 	/* Get [passage] keys */
-	foreach (string key; ["footnotes", "headings", "passage-references", "verse-numbers"]) {
+	foreach (string key; [
+		"footnotes",
+		"headings",
+		"passage-references",
+		"verse-numbers"
+	]) {
 		try
 			esv.opts.b["include-" ~ key] =
 				ini["passage"].keyAs!bool(key, "true");
 		catch (INITypeException e)
-			throw new Exception(configPath ~ ": " ~ e.msg);
+			die(configPath ~ ": " ~ e.msg);
 	}
 	/* Get line-length ([passage]) */
-	try {
+	try
 		esv.opts.i["line-length"] =
 			ini["passage"].keyAs!int("line-length", "0");
-	} catch (INITypeException e) {
+	catch (INITypeException e)
-		throw new Exception(configPath ~ ": " ~ e.msg);
+		die(configPath ~ ": " ~ e.msg);
-	}
 
 	if (fFlag) esv.opts.b["include-footnotes"]          = true;
 	if (hFlag) esv.opts.b["include-headings"]           = true;
@@ -257,17 +235,45 @@ key = %s
 	if (lFlag != 0) esv.opts.i["line-length"] = lFlag;
 
 	writeln(esv.getPassage(args[1].parseBook(), args[2]));
-	return true;
+	return 0;
+}
+
+private void
+warn(string mesg)
+{
+	stderr.writeln(baseName(mainArgs[0]) ~ ": " ~ mesg);
+}
+
+private void
+die(string mesg) @trusted
+{
+	import core.runtime : Runtime;
+	import core.stdc.stdlib : exit;
+
+	warn(mesg);
+	Runtime.terminate();
+	exit(1);
+}
+
+private void
+enforceDie(A...)(bool cond, string fmt, A a)
+{
+	import std.format : format;
+
+	if (!cond)
+		die(format(fmt, a));
 }
 
 private string
-extractOpt(in GetOptException e) @safe
+extractOpt(in GetOptException e)
 {
+	import std.regex : matchFirst;
+
 	return e.msg.matchFirst("-.")[0];
 }
 
 private string
-parseBook(in string book) @safe
+parseBook(in string book)
 {
 	import std.string : tr;