save: Fix xmlSave with NULL encoding

Regressed with cc45f618.

testparser.c

@@ -288,6 +288,50 @@ testNoBlanks(void) {
 
     return err;
 }
+
+static int
+testSaveNullEncDoc(const char *xml, const char *expect) {
+    xmlDocPtr doc;
+    xmlBufferPtr buffer;
+    xmlSaveCtxtPtr save;
+    const xmlChar *result;
+    int err = 0;
+
+    doc = xmlReadDoc(BAD_CAST xml, NULL, NULL, 0);
+
+    buffer = xmlBufferCreate();
+    save = xmlSaveToBuffer(buffer, NULL, 0);
+    xmlSaveDoc(save, doc);
+    xmlSaveClose(save);
+
+    result = xmlBufferContent(buffer);
+    if (strcmp((char *) result, expect) != 0) {
+        fprintf(stderr, "xmlSave with NULL encodíng failed\n");
+        err = 1;
+    }
+
+    xmlBufferFree(buffer);
+    xmlFreeDoc(doc);
+
+    return err;
+}
+
+static int
+testSaveNullEnc(void) {
+    int err = 0;
+
+    err |= testSaveNullEncDoc(
+        "<?xml version=\"1.0\"?><doc>\xC3\x98</doc>",
+        "<?xml version=\"1.0\"?>\n<doc>&#xD8;</doc>\n");
+    err |= testSaveNullEncDoc(
+        "<?xml version=\"1.0\" encoding=\"utf-8\"?><doc>\xC3\x98</doc>",
+        "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n<doc>\xC3\x98</doc>\n");
+    err |= testSaveNullEncDoc(
+        "<?xml version=\"1.0\" encoding=\"iso-8859-1\"?><doc>\xD8</doc>",
+        "<?xml version=\"1.0\" encoding=\"iso-8859-1\"?>\n<doc>\xD8</doc>\n");
+
+    return err;
+}
 #endif /* LIBXML_OUTPUT_ENABLED */
 
 #ifdef LIBXML_SAX1_ENABLED
@@ -1157,6 +1201,7 @@ main(void) {
 #ifdef LIBXML_OUTPUT_ENABLED
     err |= testCtxtParseContent();
     err |= testNoBlanks();
+    err |= testSaveNullEnc();
 #endif
 #ifdef LIBXML_SAX1_ENABLED
     err |= testBalancedChunk();

xmlsave.c

@@ -778,13 +778,19 @@ static int xmlSaveSwitchEncoding(xmlSaveCtxtPtr ctxt, const char *encoding) {
             xmlSaveErr(buf, res, NULL, encoding);
             return(-1);
         }
-	buf->conv = xmlBufCreate(4000 /* MINLEN */);
+
-	if (buf->conv == NULL) {
+        if (handler != NULL) {
-	    xmlCharEncCloseFunc(handler);
+            buf->conv = xmlBufCreate(4000 /* MINLEN */);
-            xmlSaveErrMemory(buf);
+            if (buf->conv == NULL) {
-	    return(-1);
+                xmlCharEncCloseFunc(handler);
-	}
+                xmlSaveErrMemory(buf);
-        buf->encoder = handler;
+                return(-1);
+            }
+            buf->encoder = handler;
+        }
+
+        ctxt->encoding = (const xmlChar *) encoding;
+
 	/*
 	 * initialize the state, e.g. if outputting a BOM
 	 */
@@ -795,11 +801,15 @@ static int xmlSaveSwitchEncoding(xmlSaveCtxtPtr ctxt, const char *encoding) {
 
 static int xmlSaveClearEncoding(xmlSaveCtxtPtr ctxt) {
     xmlOutputBufferPtr buf = ctxt->buf;
+
     xmlOutputBufferFlush(buf);
     xmlCharEncCloseFunc(buf->encoder);
     xmlBufFree(buf->conv);
     buf->encoder = NULL;
     buf->conv = NULL;
+
+    ctxt->encoding = NULL;
+
     return(0);
 }
 
@@ -1342,7 +1352,6 @@ xmlDocContentDumpOutput(xmlSaveCtxtPtr ctxt, xmlDocPtr cur) {
     const xmlChar *oldctxtenc = ctxt->encoding;
     const xmlChar *encoding = ctxt->encoding;
     xmlOutputBufferPtr buf = ctxt->buf;
-    xmlCharEncoding enc;
     int switched_encoding = 0;
 
     xmlInitParser();
@@ -1370,6 +1379,7 @@ xmlDocContentDumpOutput(xmlSaveCtxtPtr ctxt, xmlDocPtr cur) {
 	    if (xmlSaveSwitchEncoding(ctxt, (const char*) encoding) < 0) {
 		return(-1);
 	    }
+            switched_encoding = 1;
 	}
         if (ctxt->options & XML_SAVE_FORMAT)
 	    htmlDocContentDumpFormatOutput(buf, cur,
@@ -1377,29 +1387,23 @@ xmlDocContentDumpOutput(xmlSaveCtxtPtr ctxt, xmlDocPtr cur) {
 	else
 	    htmlDocContentDumpFormatOutput(buf, cur,
 	                                   (const char *)encoding, 0);
-	return(0);
 #else
         return(-1);
 #endif
     } else if ((cur->type == XML_DOCUMENT_NODE) ||
                (ctxt->options & XML_SAVE_AS_XML) ||
                (ctxt->options & XML_SAVE_XHTML)) {
-	enc = xmlParseCharEncoding((const char*) encoding);
 	if ((encoding != NULL) && (oldctxtenc == NULL) &&
 	    (buf->encoder == NULL) && (buf->conv == NULL) &&
 	    ((ctxt->options & XML_SAVE_NO_DECL) == 0)) {
-	    if ((enc != XML_CHAR_ENCODING_UTF8) &&
+            /*
-		(enc != XML_CHAR_ENCODING_NONE) &&
+             * we need to switch to this encoding but just for this
-		(enc != XML_CHAR_ENCODING_ASCII)) {
+             * document since we output the XMLDecl the conversion
-		/*
+             * must be done to not generate not well formed documents.
-		 * we need to switch to this encoding but just for this
+             */
-		 * document since we output the XMLDecl the conversion
+            if (xmlSaveSwitchEncoding(ctxt, (const char *) encoding) < 0)
-		 * must be done to not generate not well formed documents.
+                return(-1);
-		 */
+            switched_encoding = 1;
-		if (xmlSaveSwitchEncoding(ctxt, (const char*) encoding) < 0)
-		    return(-1);
-		switched_encoding = 1;
-	    }
 	}