ext/iconv/tests/bug48147.phpt: whitelist iconvs with //IGNORE

This test is for the behavior of iconv's magic "//IGNORE" suffix. The
output it expects agrees with POSIX 2024 even when the underlying
implementation (glibc) does not. A comment has been added to this
effect, and two calls to urlencode() have been removed so that two
(expected) errors are not swallowed.

Afterwards, we whitelist the two iconv implementations that are known
to support //IGNORE. While POSIX standardizes its behavior, it falls
short of requiring implementations to support it. Musl in particular
does not support any suffix.

Author: orlitzky

ext/iconv/tests/bug48147.phpt

@@ -2,26 +2,50 @@
 Bug #48147 (iconv with //IGNORE cuts the string)
 --EXTENSIONS--
 iconv
+--SKIPIF--
+<?php
+/*
+ * POSIX 2024 specifies how the "//IGNORE" suffix should behave, but
+ * falls short of requiring implementations to support it (iconv_open
+ * is allowed to return EINVAL for a suffix it does not recognize).
+ *
+ * Many implementations still do not support it, which is OK. We
+ * whitelist the ones that are known to.
+ */
+if (ICONV_IMPL != "glibc" && ICONV_IMPL != "libiconv") {
+    die("skip iconv implementation may not support //IGNORE");
+}
+?>
 --FILE--
 <?php
+/*
+ * POSIX says that when //IGNORE is specified, invalid bytes followed
+ * by valid bytes "shall not be treated as an error." GNU iconv does
+ * not follow this convention, but PHP does the right thing. In the
+ * examples below, invalid bytes in the middle of the string get
+ * dropped, and a string is returned. The two examples where the
+ * problem is at the end do not qualify for the "shall not" exception
+ * because there are no VALID bytes after the error. So PHP is morally
+ * correct in those cases to return an error (false).
+ */
 $text = "aa\xC3\xC3\xC3\xB8aa";
 var_dump(iconv("UTF-8", "UTF-8", $text));
 var_dump(urlencode(iconv("UTF-8", "UTF-8//IGNORE", $text)));
 // only invalid
-var_dump(urlencode(iconv("UTF-8", "UTF-8//IGNORE", "\xC3")));
+var_dump(iconv("UTF-8", "UTF-8//IGNORE", "\xC3"));
 // start invalid
 var_dump(urlencode(iconv("UTF-8", "UTF-8//IGNORE", "\xC3\xC3\xC3\xB8aa")));
 // finish invalid
-var_dump(urlencode(iconv("UTF-8", "UTF-8//IGNORE", "aa\xC3\xC3\xC3")));
+var_dump(iconv("UTF-8", "UTF-8//IGNORE", "aa\xC3\xC3\xC3"));
 ?>
 --EXPECTF--
 Notice: iconv(): Detected an illegal character in input string in %s on line %d
 bool(false)
 string(10) "aa%C3%B8aa"
 
 Notice: iconv(): Detected an incomplete multibyte character in input string in %s on line %d
-string(0) ""
+bool(false)
 string(8) "%C3%B8aa"
 
 Notice: iconv(): Detected an incomplete multibyte character in input string in %s on line %d
-string(0) ""
+bool(false)