From 6eec862df222c8d060e8482dd09d0f91197ee9fc Mon Sep 17 00:00:00 2001
From: Thomas Voss <mail@thomasvoss.com>
Date: Mon, 19 Feb 2024 01:36:55 +0100
Subject: Better error messages in the lexer

---
 src/common/cerr.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++-----
 src/common/cerr.h |   7 ++++
 2 files changed, 102 insertions(+), 8 deletions(-)

(limited to 'src/common')

diff --git a/src/common/cerr.c b/src/common/cerr.c
index 8570247..819df4a 100644
--- a/src/common/cerr.c
+++ b/src/common/cerr.c
@@ -1,19 +1,33 @@
 #include <errno.h>
 #include <stdarg.h>
+#include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
+#include <mbstring.h>
+
 #include "cerr.h"
+#include "macros.h"
+#include "mbstring.h"
+
+#define TAB_AS_SPC "        "
+
+#define EOLS8  u8"\n\v\f\r\x85\u2028\u2029"
+#define EOLS32 U"\n\v\f\r\x85\u2028\u2029"
 
 #define SGR_BOLD "\33[1m"
 #define SGR_DONE "\33[0m"
+#define SGR_WARN "\33[1;35m"
+#define SGR_ERR  "\33[1;31m"
+
+int sizelen(size_t);
 
 static bool color;
 static const char *progname;
 
-static const char *_bold, *_done;
+static const char *_bold, *_done, *_warn, *_err;
 
 void
 cerrinit(const char *s)
@@ -23,17 +37,16 @@ cerrinit(const char *s)
 
 	if (isatty(STDOUT_FILENO)) {
 		const char *ev = getenv("NO_COLOR");
-		if (!ev || !*ev)
-			color = true;
+		color = !ev || !*ev;
 	}
 
 	if (color) {
 		_bold = SGR_BOLD;
 		_done = SGR_DONE;
-	} else {
-		_bold = "";
-		_done = "";
-	}
+		_warn = SGR_WARN;
+		_err = SGR_ERR;
+	} else
+		_bold = _done = _warn = _err = "";
 }
 
 void
@@ -71,10 +84,84 @@ die_with_off(const char *file, size_t off, const char *fmt, ...)
 	va_list ap;
 
 	va_start(ap, fmt);
-	fprintf(stderr, "%s%s:%s:%zu:%s ", _bold, progname, file, off, _done);
+	fprintf(stderr, "%s%s: %s:%zu:%s %serror:%s ", _bold, progname, file, off,
+	        _done, _err, _done);
+	vfprintf(stderr, fmt, ap);
+	fputc('\n', stderr);
+	va_end(ap);
+
+	exit(EXIT_FAILURE);
+}
+
+void
+die_at_pos_with_code(const char *file, struct u8view sv, struct u8view hl,
+                     size_t off, const char *fmt, ...)
+{
+	int w;
+	rune _;
+	size_t lb;
+	va_list ap;
+	const char8_t *prv, *end;
+
+	va_start(ap, fmt);
+	fprintf(stderr, "%s%s: %s:%zu:%s %serror:%s ", _bold, progname, file, off,
+	        _done, _err, _done);
 	vfprintf(stderr, fmt, ap);
 	fputc('\n', stderr);
 	va_end(ap);
 
+	for (lb = 0, prv = end = sv.p; end <= sv.p + off; lb++) {
+		prv = end;
+		end += u8cbspn(end, sv.p + sv.len - end, EOLS32, lengthof(EOLS32) - 1);
+		end += u8tor_uc(&_, end);
+	}
+
+	u8prev(&_, &end, prv);
+	w = sizelen(lb);
+	w = MAX(w, 4);
+
+	fprintf(stderr, " %*zu │ ", w, lb);
+
+	/* The following is really ugly, but it works! */
+	if (hl.p) {
+		ptrdiff_t w2 = hl.p - prv;
+		struct u8view pfx = {prv, w2};
+
+		for (ptrdiff_t i = 0; i < w2; i++) {
+			if (prv[i] == '\t')
+				fputs(TAB_AS_SPC, stderr);
+			else
+				fputc(prv[i], stderr);
+		}
+		fprintf(stderr, "%s%.*s%s%.*s\n", _err, U8_PRI_ARGS(hl), _done,
+		        (int)(end - (prv + w2 + hl.len)), prv + w2 + hl.len);
+		fprintf(stderr, " %*c │ ", w, ' ');
+
+		while (u8next(&_, &pfx.p, &pfx.len)) {
+			if (_ == '\t')
+				fputs(TAB_AS_SPC, stderr);
+			else
+				fputc(' ', stderr);
+		}
+
+		fprintf(stderr, "%s^", _err);
+		for (u8next(&_, &hl.p, &hl.len); u8next(&_, &hl.p, &hl.len);
+		     fputc('~', stderr))
+			;
+		fprintf(stderr, "%s\n", _done);
+	} else {
+		fprintf(stderr, "%.*s\n", (int)(end - prv), prv);
+		fprintf(stderr, " %*c │\n", w, ' ');
+	}
+
 	exit(EXIT_FAILURE);
 }
+
+int
+sizelen(size_t x)
+{
+	int n;
+	for (n = 0; x; x /= 10, n++)
+		;
+	return n;
+}
diff --git a/src/common/cerr.h b/src/common/cerr.h
index 869c9e2..5476f96 100644
--- a/src/common/cerr.h
+++ b/src/common/cerr.h
@@ -3,6 +3,8 @@
 
 #include <stddef.h>
 
+#include <mbstring.h>
+
 void cerrinit(const char *);
 
 [[noreturn, gnu::nonnull, gnu::format(printf, 1, 2)]]
@@ -14,4 +16,9 @@ void diex(const char *, ...);
 [[noreturn, gnu::nonnull, gnu::format(printf, 3, 4)]]
 void die_with_off(const char *, size_t, const char *, ...);
 
+[[noreturn, gnu::nonnull, gnu::format(printf, 5, 6)]]
+void
+die_at_pos_with_code(const char *, struct u8view, struct u8view, size_t,
+                     const char *, ...);
+
 #endif /* !AHOY_COMMON_CERR_H */
-- 
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