Fix grapheme breaks on string-initial (#205)

* Fix extended emoji + zwj combo

* Patch initial repeated regional flags and extended+zwj emoj

* Merge conditions for setting breaks bt region

* updated fix

* perform tests for both utf8proc_map and manual calls to utf8proc_grapheme_break_stateful

* consolidate tests

Co-authored-by: Thomas Marks <marksta@umich.edu>

test/graphemetest.c

@@ -1,20 +1,10 @@
 #include "tests.h"
 
-int main(int argc, char **argv)
-{
-    unsigned char buf[8192];
-    FILE *f = argc > 1 ? fopen(argv[1], "r") : NULL;
-    utf8proc_uint8_t src[1024];
-
-    check(f != NULL, "error opening GraphemeBreakTest.txt");
-    while (simple_getline(buf, f) > 0) {
+/* check one line in the format of GraphemeBreakTest.txt */
+void checkline(const char *_buf, bool verbose) {
     size_t bi = 0, si = 0;
-        lineno += 1;
-
-        if (lineno % 100 == 0)
-            printf("checking line %zd...\n", lineno);
-
-        if (buf[0] == '#') continue;
+    utf8proc_uint8_t src[1024]; /* more than long enough for all of our tests */
+    const unsigned char *buf = (const unsigned char *) _buf;
 
     while (buf[bi]) {
         bi = skipspaces(buf, bi);
@@ -28,6 +18,10 @@ int main(int argc, char **argv)
         else if (buf[bi] == '#') { /* start of comments */
             break;
         }
+        else if (buf[bi] == '/') { /* for convenience, also accept / as grapheme break */
+            src[si++] = '/';
+            bi += 1;
+        }
         else { /* hex-encoded codepoint */
             size_t len = encode((unsigned char*) (src + si), buf + bi) - 1;
             while (src[si]) ++si; /* advance to NUL termination */
@@ -38,7 +32,7 @@ int main(int argc, char **argv)
         --si; /* no break after final grapheme */
     src[si] = 0; /* NUL-terminate */
 
-        if (si) {
+    if (si) { /* test utf8proc_map */
         utf8proc_uint8_t utf8[1024]; /* copy src without 0xff grapheme separators */
         size_t i = 0, j = 0;
         utf8proc_ssize_t glen, k;
@@ -65,10 +59,49 @@ int main(int argc, char **argv)
         }
         free(g);
     }
+
+    if (si) { /* test manual calls to utf8proc_grapheme_break_stateful */
+        utf8proc_int32_t state = 0, prev_codepoint = 0;
+        size_t i = 0;
+        utf8proc_bool expectbreak = false;
+        do {
+            utf8proc_int32_t codepoint;
+            i += utf8proc_iterate(src + i, si - i, &codepoint);
+            check(codepoint >= 0, "invalid UTF-8 data");
+            if (codepoint == 0x002F)
+                expectbreak = true;
+            else {
+                if (prev_codepoint != 0) {
+                    check(expectbreak == utf8proc_grapheme_break_stateful(prev_codepoint, codepoint, &state),
+                          "grapheme mismatch: between 0x%04x and 0x%04x in \"%s\"", prev_codepoint, codepoint, (char*) src);
+                }
+                expectbreak = false;
+                prev_codepoint = codepoint;
+            }
+        } while (i < si);
+    }
+
+    if (verbose)
+        printf("passed grapheme test: \"%s\"\n", (char*) src);
+}
+
+int main(int argc, char **argv)
+{
+    unsigned char buf[8192];
+    FILE *f = argc > 1 ? fopen(argv[1], "r") : NULL;
+
+    check(f != NULL, "error opening GraphemeBreakTest.txt");
+    while (simple_getline(buf, f) > 0) {
+        if ((++lineno) % 100 == 0)
+            printf("checking line %zd...\n", lineno);
+        if (buf[0] == '#') continue;
+        checkline((char *) buf, false);
     }
     fclose(f);
     printf("Passed tests after %zd lines!\n", lineno);
 
+    printf("Performing regression tests...\n");
+
     /* issue 144 */
     {
         utf8proc_uint8_t input[] = {0xef,0xbf,0xbf,0xef,0xbf,0xbe,0x00}; /* "\uffff\ufffe" */
@@ -80,5 +113,12 @@ int main(int argc, char **argv)
         free(g);
     };
 
+    /* https://github.com/JuliaLang/julia/issues/37680 */
+    checkline("/ 1f1f8 1f1ea / 1f1f8 1f1ea /", true); /* Two swedish flags after each other */
+    checkline("/ 1f926 1f3fc 200d 2642 fe0f /", true); /* facepalm + pale skin + zwj + male sign + FE0F */
+    checkline("/ 1f468 1f3fb 200d 1f91d 200d 1f468 1f3fd /", true); /* man face + pale skin + zwj + hand holding + zwj + man face + dark skin */
+
+    printf("Passed regression tests!\n");
+
     return 0;
 }

utf8proc.c

@@ -290,8 +290,11 @@ static utf8proc_bool grapheme_break_simple(int lbc, int tbc) {
 
 static utf8proc_bool grapheme_break_extended(int lbc, int tbc, utf8proc_int32_t *state)
 {
-  int lbc_override = ((state && *state != UTF8PROC_BOUNDCLASS_START)
-                      ? *state : lbc);
+  int lbc_override;
+  if (*state == UTF8PROC_BOUNDCLASS_START)
+    *state = lbc_override = lbc; 
+  else
+    lbc_override = *state;
   utf8proc_bool break_permitted = grapheme_break_simple(lbc_override, tbc);
   if (state) {
     // Special support for GB 12/13 made possible by GB999. After two RI