dns/resource: add error messages

These new error messages will help users
more easily craft Resources. The error messages
will be returned via the `validateresource` RPC.

lib/dns/resource.js

@@ -349,11 +349,11 @@ class Resource extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(Array.isArray(json.records));
+    assert(json && typeof json === 'object', 'Invalid json.');
+    assert(Array.isArray(json.records), 'Invalid records.');
 
     for (const item of json.records) {
-      assert(item && typeof item === 'object');
+      assert(item && typeof item === 'object', 'Invalid record.');
 
       const RD = stringToClass(item.type);
 
@@ -437,13 +437,19 @@ class DS extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'DS');
-    assert((json.keyTag & 0xffff) === json.keyTag);
-    assert((json.algorithm & 0xff) === json.algorithm);
-    assert((json.digestType & 0xff) === json.digestType);
-    assert(typeof json.digest === 'string');
-    assert((json.digest.length >>> 1) <= 255);
+    assert(json && typeof json === 'object', 'Invalid DS record.');
+    assert(json.type === 'DS',
+      'Invalid DS record. Property "type" must be "DS".');
+    assert((json.keyTag & 0xffff) === json.keyTag,
+      'Invalid DS record. Property "keyTag" must be a u16.');
+    assert((json.algorithm & 0xff) === json.algorithm,
+      'Invalid DS record. Property "algorithm" must be a u8.');
+    assert((json.digestType & 0xff) === json.digestType,
+      'Invalid DS record. Property "digestType" must be a u8.');
+    assert(typeof json.digest === 'string',
+      'Invalid DS record. Propery "digest" must be a String.');
+    assert((json.digest.length >>> 1) <= 255,
+      'Invalid DS record. Property "digest" is too large.');
 
     this.keyTag = json.keyTag;
     this.algorithm = json.algorithm;
@@ -495,9 +501,12 @@ class NS extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'NS');
-    assert(isName(json.ns));
+    assert(json && typeof json === 'object',
+      'Invalid NS record.');
+    assert(json.type === 'NS',
+      'Invalid NS record. Property "type" must be "NS".');
+    assert(isName(json.ns),
+      'Invalid NS record. Property "ns" must be a valid name.');
 
     this.ns = json.ns;
 
@@ -554,10 +563,13 @@ class GLUE4 extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'GLUE4');
-    assert(isName(json.ns));
-    assert(IP.isIPv4String(json.address));
+    assert(json && typeof json === 'object', 'Invalid GLUE4 record.');
+    assert(json.type === 'GLUE4',
+      'Invalid GLUE4 record. Property "type" must be "GLUE4".');
+    assert(isName(json.ns),
+      'Invalid GLUE4 record. Property "ns" must be valid name.');
+    assert(IP.isIPv4String(json.address),
+      'Invalid GLUE4 record. Property "address" must be a IPv4 address.');
 
     this.ns = json.ns;
     this.address = IP.normalize(json.address);
@@ -615,10 +627,13 @@ class GLUE6 extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'GLUE6');
-    assert(isName(json.ns));
-    assert(IP.isIPv6String(json.address));
+    assert(json && typeof json === 'object', 'Invalid GLUE6 record.');
+    assert(json.type === 'GLUE6',
+      'Invalid GLUE6 record. Property "type" must be "GLUE6".');
+    assert(isName(json.ns),
+      'Invalid GLUE6 record. Property "ns" must be valid name.');
+    assert(IP.isIPv6String(json.address),
+      'Invalid GLUE6 record. Property "address" must be a IPv6 address.');
 
     this.ns = json.ns;
     this.address = IP.normalize(json.address);
@@ -677,9 +692,11 @@ class SYNTH4 extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'SYNTH4');
-    assert(IP.isIPv4String(json.address));
+    assert(json && typeof json === 'object', 'Invalid SYNTH4 record.');
+    assert(json.type === 'SYNTH4',
+      'Invalid SYNTH4 record. Property "type" must be "SYNTH4".');
+    assert(IP.isIPv4String(json.address),
+      'Invalid SYNTH4 record. Property "address" must be a IPv4 address.');
 
     this.address = IP.normalize(json.address);
 
@@ -737,9 +754,11 @@ class SYNTH6 extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'SYNTH6');
-    assert(IP.isIPv6String(json.address));
+    assert(json && typeof json === 'object', 'Invalid SYNTH6 record.');
+    assert(json.type === 'SYNTH6',
+      'Invalid SYNTH6 record. Property "type" must be "SYNTH6".');
+    assert(IP.isIPv6String(json.address),
+      'Invalid SYNTH6 record. Property "address" must be a IPv6 address.');
 
     this.address = IP.normalize(json.address);
 
@@ -812,13 +831,18 @@ class TXT extends Struct {
   }
 
   fromJSON(json) {
-    assert(json && typeof json === 'object');
-    assert(json.type === 'TXT');
-    assert(Array.isArray(json.txt));
+    assert(json && typeof json === 'object',
+      'Invalid TXT record.');
+    assert(json.type === 'TXT',
+      'Invalid TXT record. Property "type" must be "TXT".');
+    assert(Array.isArray(json.txt),
+      'Invalid TXT record. Property "txt" must be an Array.');
 
     for (const txt of json.txt) {
-      assert(typeof txt === 'string');
-      assert(txt.length <= 255);
+      assert(typeof txt === 'string',
+        'Invalid TXT record. Entries in "txt" Array must be strings.');
+      assert(txt.length <= 255,
+        'Invalid TXT record. Entries in "txt" Array must be <= 255 in length.');
 
       this.txt.push(txt);
     }