dns: allow NODE_DNS_VERBATIM to change default verbatim

Allow the NODE_DNS_VERBATIM environment variable to change the default
value of `verbatim` in `dns.lookup()`.

Author: oyyd

doc/api/cli.md

@@ -1295,6 +1295,15 @@ added: v0.3.0
 
 When set, colors will not be used in the REPL.
 
+### `NODE_DNS_VERBATIM=[0, 1]`
+<!-- YAML
+added: REPLACEME
+-->
+
+Set the default value of `verbatim` in [`dns.lookup()`][]. The value may be:
+* `0` to indicate `false`
+* `1` to indicate `true`
+
 ### `NODE_EXTRA_CA_CERTS=file`
 <!-- YAML
 added: v7.3.0
@@ -1728,6 +1737,7 @@ $ node --max-old-space-size=1536 index.js
 [`NODE_OPTIONS`]: #cli_node_options_options
 [`NO_COLOR`]: https://no-color.org
 [`SlowBuffer`]: buffer.md#buffer_class_slowbuffer
+[`dns.lookup()`]: dns.html#dns_dns_lookup_hostname_options_callback
 [`process.setUncaughtExceptionCaptureCallback()`]: process.md#process_process_setuncaughtexceptioncapturecallback_fn
 [`tls.DEFAULT_MAX_VERSION`]: tls.md#tls_tls_default_max_version
 [`tls.DEFAULT_MIN_VERSION`]: tls.md#tls_tls_default_min_version

lib/dns.js

@@ -41,6 +41,7 @@ const {
   Resolver,
   validateHints,
   emitInvalidHostnameWarning,
+  getDefaultVerbatim,
 } = require('internal/dns/utils');
 const {
   ERR_INVALID_ARG_TYPE,
@@ -96,7 +97,7 @@ function lookup(hostname, options, callback) {
   let hints = 0;
   let family = -1;
   let all = false;
-  let verbatim = false;
+  let verbatim = getDefaultVerbatim();
 
   // Parse arguments
   if (hostname) {

lib/internal/dns/promises.js

@@ -1,5 +1,4 @@
 'use strict';
-
 const {
   ArrayPrototypeMap,
   ObjectCreate,
@@ -14,6 +13,7 @@ const {
   validateHints,
   validateTimeout,
   emitInvalidHostnameWarning,
+  getDefaultVerbatim,
 } = require('internal/dns/utils');
 const { codes, dnsException } = require('internal/errors');
 const { toASCII } = require('internal/idna');
@@ -103,7 +103,7 @@ function lookup(hostname, options) {
   var hints = 0;
   var family = -1;
   var all = false;
-  var verbatim = false;
+  var verbatim = getDefaultVerbatim();
 
   // Parse arguments
   if (hostname && typeof hostname !== 'string') {

lib/internal/dns/utils.js

@@ -184,6 +184,17 @@ function emitInvalidHostnameWarning(hostname) {
   );
 }
 
+function getDefaultVerbatim() {
+  const { NODE_DNS_VERBATIM } = process.env;
+  switch (NODE_DNS_VERBATIM) {
+    case '1':
+      return true;
+    case '0':
+    default:
+      return false;
+  }
+}
+
 module.exports = {
   bindDefaultResolver,
   getDefaultResolver,
@@ -192,4 +203,5 @@ module.exports = {
   validateTimeout,
   Resolver,
   emitInvalidHostnameWarning,
+  getDefaultVerbatim,
 };

lib/internal/main/print_help.js

@@ -38,6 +38,8 @@ const envVars = new SafeMap(ArrayPrototypeConcat([
     'categories that should print debug output' }],
   ['NODE_DISABLE_COLORS', { helpText: 'set to 1 to disable colors in ' +
     'the REPL' }],
+  ['NODE_DNS_VERBATIM', { helpText: 'set to 1 or 0 to enable or disable ' +
+    'verbatim in dns.lookup by default' }],
   ['NODE_EXTRA_CA_CERTS', { helpText: 'path to additional CA certificates ' +
     'file. Only read once during process startup.' }],
   ['NODE_NO_WARNINGS', { helpText: 'set to 1 to silence process warnings' }],

test/parallel/test-dns-default-verbatim.js

@@ -0,0 +1,50 @@
+// Flags: --expose-internals
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const { internalBinding } = require('internal/test/binding');
+const cares = internalBinding('cares_wrap');
+const { promisify } = require('util')
+
+// Test that NODE_DNS_VERBATIM works as expected.
+
+const originalGetaddrinfo = cares.getaddrinfo;
+const calls = [];
+cares.getaddrinfo = (...args) => {
+  calls.push(args);
+  originalGetaddrinfo(...args);
+};
+
+const dns = require('dns');
+const dnsPromises = dns.promises;
+
+(async () => {
+  {
+    process.env.NODE_DNS_VERBATIM = '1';
+    let verbatim;
+
+    await promisify(dns.lookup)('example.org');
+
+    assert.strictEqual(calls.length, 1);
+    verbatim = calls[0][4];
+    assert.strictEqual(verbatim, true);
+
+    await dnsPromises.lookup('example.org');
+    assert.strictEqual(calls.length, 2);
+    verbatim = calls[1][4];
+    assert.strictEqual(verbatim, true);
+
+    process.env.NODE_DNS_VERBATIM = '0';
+
+    await promisify(dns.lookup)('example.org');
+
+    assert.strictEqual(calls.length, 3);
+    verbatim = calls[2][4];
+    assert.strictEqual(verbatim, false);
+
+    await dnsPromises.lookup('example.org');
+    assert.strictEqual(calls.length, 4);
+    verbatim = calls[3][4];
+    assert.strictEqual(verbatim, false);
+  }
+})();