Add a fallback argument to j.unquote()

src/vmod_j.c

@@ -504,8 +504,15 @@ vmod_object(VRT_CTX, VCL_STRANDS s)
 	return (p + 1);
 }
 
+#define fail(ctx, fallback, ...) do {					\
+		if (fallback != NULL)					\
+			VSLb(ctx->vsl, SLT_Error, __VA_ARGS__);	\
+		else							\
+			VRT_fail(ctx, __VA_ARGS__);			\
+	} while(0)
+
 VCL_STRING
-vmod_unquote(VRT_CTX, VCL_STRING p)
+vmod_unquote(VRT_CTX, VCL_STRING p, VCL_STRING fallback)
 {
 	struct vsb vsb[1];
 	const char *err = NULL;
@@ -515,15 +522,15 @@ vmod_unquote(VRT_CTX, VCL_STRING p)
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 
 	if (*p != '"' || p[strlen(p) - 1] != '"') {
-		VRT_fail(ctx, "j.unquote() argument missing quotes");
-		return (NULL);
+		fail(ctx, fallback, "j.unquote() argument missing quotes");
+		return (fallback);
 	}
 	p++;
 
 	WS_VSB_new(vsb, ctx->ws);
 	if (vsbjunquot(vsb, p, &err) && err != NULL) {
-		VRT_fail(ctx, "j.unquote() error at: ...%.10s", err);
-		return (NULL);
+		fail(ctx, fallback, "j.unquote() error at: ...%.10s", err);
+		return (fallback);
 	}
 	r = WS_VSB_finish(vsb, ctx->ws, NULL);
 	if (r == NULL) {

src/vmod_j.man.rst

@@ -39,7 +39,7 @@ SYNOPSIS
   
   STRING object(STRING)
   
-  STRING unquote(STRING)
+  STRING unquote(STRING, STRING fallback)
   
 
 INTRODUCTION
@@ -404,10 +404,13 @@ Deprecated alias for ``object()``.
 
 .. _j.unquote():
 
-STRING unquote(STRING)
-----------------------
+STRING unquote(STRING, STRING fallback=0)
+-----------------------------------------
+
+Utility function to decode JSON strings into UTF-8.
 
-Utility function to decode JSON strings into UTF-8
+If decoding fails and *fallback* is provided, the error is logged with
+tag ``Error`` and *fallback* is returned. Otherwise, the VCL is failed.
 
 
 WARNING

src/vmod_j.vcc

@@ -339,9 +339,12 @@ concatenation argument (strands) as key/value pairs.
 
 $Alias obj object
 
-$Function STRING unquote(STRING)
+$Function STRING unquote(STRING, STRING fallback=0)
 
-Utility function to decode JSON strings into UTF-8
+Utility function to decode JSON strings into UTF-8.
+
+If decoding fails and *fallback* is provided, the error is logged with
+tag ``Error`` and *fallback* is returned. Otherwise, the VCL is failed.
 
 
 WARNING

src/vtc/vmod_j.vtc

@@ -108,6 +108,10 @@ varnish v1 -vcl {
 		    "C" + j.array("A" + 2 + j.object(j.nil()))
 		    );
 		set resp.http.o4 = j.object(j.string("A") + j.object(j.nil()));
+
+		set resp.http.unok = j.unquote({""abc""});
+		set resp.http.unno = j.unquote("", j.null());
+
 		set resp.body = "";
 		return (deliver);
 	}
@@ -156,6 +160,9 @@ client c1 {
 	expect resp.http.o3 == \
 	       "{\"A\":null,\"B\":{\"BB\":42.42e42,\"CC\":false,\"DD\":true},\"C\":[\"A\",2,{}]}"
 	expect resp.http.o4 == "{\"A\":{}}"
+
+	expect resp.http.unok == "abc"
+	expect resp.http.unno == "null"
 } -start
 
 logexpect l2 -v v1 -q "ReqURL ~ \"^/e-badutf\"" {