fix: backport emitWarning helper

Unify the way we print out messages relating to upcoming changes
or potential misuse of the driver. Using the emitWarning API allows
users to configure when and how messages are shown.

NODE-2317

Author: nbbeeken

.eslintrc.json

@@ -21,7 +21,7 @@
     "es/no-destructuring": "error",
     "es/no-rest-spread-properties": "error",
     "es/no-spread-elements": "error",
-    "no-console": "off",
+    "no-console": "error",
     "eqeqeq": ["error", "always", { "null": "ignore" }],
     "strict": ["error", "global"]
   },

lib/collection.js

@@ -2,6 +2,7 @@
 
 const deprecate = require('util').deprecate;
 const deprecateOptions = require('./utils').deprecateOptions;
+const emitWarningOnce = require('./utils').emitWarningOnce;
 const checkCollectionName = require('./utils').checkCollectionName;
 const ObjectID = require('./core').BSON.ObjectID;
 const MongoError = require('./core').MongoError;
@@ -323,7 +324,7 @@ Collection.prototype.find = deprecateOptions(
   function(query, options, callback) {
     if (typeof callback === 'object') {
       // TODO(MAJOR): throw in the future
-      console.warn('Third parameter to `find()` must be a callback or undefined');
+      emitWarningOnce('Third parameter to `find()` must be a callback or undefined');
     }
 
     let selector = query;
@@ -1092,7 +1093,7 @@ Collection.prototype.findOne = deprecateOptions(
   function(query, options, callback) {
     if (typeof callback === 'object') {
       // TODO(MAJOR): throw in the future
-      console.warn('Third parameter to `findOne()` must be a callback or undefined');
+      emitWarningOnce('Third parameter to `findOne()` must be a callback or undefined');
     }
 
     if (typeof query === 'function') (callback = query), (query = {}), (options = {});

lib/core/auth/scram.js

@@ -4,6 +4,7 @@ const Buffer = require('safe-buffer').Buffer;
 const retrieveBSON = require('../connection/utils').retrieveBSON;
 const MongoError = require('../error').MongoError;
 const AuthProvider = require('./auth_provider').AuthProvider;
+const emitWarningOnce = require('../../utils').emitWarning;
 
 const BSON = retrieveBSON();
 const Binary = BSON.Binary;
@@ -24,7 +25,7 @@ class ScramSHA extends AuthProvider {
   prepare(handshakeDoc, authContext, callback) {
     const cryptoMethod = this.cryptoMethod;
     if (cryptoMethod === 'sha256' && saslprep == null) {
-      console.warn('Warning: no saslprep library specified. Passwords will not be sanitized');
+      emitWarningOnce('Warning: no saslprep library specified. Passwords will not be sanitized');
     }
 
     crypto.randomBytes(24, (err, nonce) => {

lib/core/connection/logger.js

@@ -37,6 +37,7 @@ var Logger = function(className, options) {
   if (options.logger) {
     currentLogger = options.logger;
   } else if (currentLogger == null) {
+    // eslint-disable-next-line no-console
     currentLogger = console.log;
   }
 

lib/core/connection/msg.js

@@ -31,6 +31,7 @@ const Buffer = require('safe-buffer').Buffer;
 const opcodes = require('../wireprotocol/shared').opcodes;
 const databaseNamespace = require('../wireprotocol/shared').databaseNamespace;
 const ReadPreference = require('../topologies/read_preference');
+const emitWarning = require('../../utils').emitWarning;
 
 // Incrementing request id
 let _requestId = 0;
@@ -196,7 +197,7 @@ class BinMsg {
     while (this.index < this.data.length) {
       const payloadType = this.data.readUInt8(this.index++);
       if (payloadType === 1) {
-        console.error('TYPE 1');
+        emitWarning('TYPE 1'); // ???
       } else if (payloadType === 0) {
         const bsonSize = this.data.readUInt32LE(this.index);
         const bin = this.data.slice(this.index, this.index + bsonSize);

lib/core/sdam/topology.js

@@ -27,6 +27,7 @@ const ServerSessionPool = require('../sessions').ServerSessionPool;
 const makeClientMetadata = require('../utils').makeClientMetadata;
 const CMAP_EVENT_NAMES = require('../../cmap/events').CMAP_EVENT_NAMES;
 const compareTopologyVersion = require('./server_description').compareTopologyVersion;
+const emitWarning = require('../../utils').emitWarning;
 
 const common = require('./common');
 const drainTimerQueue = common.drainTimerQueue;
@@ -739,7 +740,7 @@ class Topology extends EventEmitter {
   }
 
   unref() {
-    console.log('not implemented: `unref`');
+    emitWarning('not implemented: `unref`');
   }
 
   // NOTE: There are many places in code where we explicitly check the last isMaster

lib/core/tools/smoke_plugin.js

@@ -52,6 +52,7 @@ exports.attachToRunner = function(runner, outputFile) {
     fs.writeFileSync(outputFile, JSON.stringify(smokeOutput));
 
     // Standard NodeJS uncaught exception handler
+    // eslint-disable-next-line no-console
     console.error(err.stack);
     process.exit(1);
   });

lib/core/topologies/read_preference.js

@@ -1,4 +1,5 @@
 'use strict';
+const emitWarningOnce = require('../../utils').emitWarningOnce;
 
 /**
  * The **ReadPreference** class is a class that represents a MongoDB ReadPreference and is
@@ -20,7 +21,7 @@ const ReadPreference = function(mode, tags, options) {
 
   // TODO(major): tags MUST be an array of tagsets
   if (tags && !Array.isArray(tags)) {
-    console.warn(
+    emitWarningOnce(
       'ReadPreference tags must be an array, this will change in the next major version'
     );
 

lib/core/uri_parser.js

@@ -4,6 +4,7 @@ const qs = require('querystring');
 const dns = require('dns');
 const MongoParseError = require('./error').MongoParseError;
 const ReadPreference = require('./topologies/read_preference');
+const emitWarningOnce = require('../utils').emitWarningOnce;
 
 /**
  * The following regular expression validates a connection string and breaks the
@@ -438,7 +439,7 @@ function parseQueryString(query, options) {
   // special cases for known deprecated options
   if (result.wtimeout && result.wtimeoutms) {
     delete result.wtimeout;
-    console.warn('Unsupported option `wtimeout` specified');
+    emitWarningOnce('Unsupported option `wtimeout` specified');
   }
 
   return Object.keys(result).length ? result : null;

lib/core/wireprotocol/kill_cursors.js

@@ -5,6 +5,7 @@ const MongoError = require('../error').MongoError;
 const MongoNetworkError = require('../error').MongoNetworkError;
 const collectionNamespace = require('./shared').collectionNamespace;
 const maxWireVersion = require('../utils').maxWireVersion;
+const emitWarning = require('../utils').emitWarning;
 const command = require('./command');
 
 function killCursors(server, ns, cursorState, callback) {
@@ -31,7 +32,7 @@ function killCursors(server, ns, cursorState, callback) {
         if (typeof callback === 'function') {
           callback(err, null);
         } else {
-          console.warn(err);
+          emitWarning(err);
         }
       }
     }

lib/operations/add_user.js

@@ -6,6 +6,7 @@ const defineAspects = require('./operation').defineAspects;
 const crypto = require('crypto');
 const handleCallback = require('../utils').handleCallback;
 const toError = require('../utils').toError;
+const emitWarning = require('../utils').emitWarning;
 
 class AddUserOperation extends CommandOperation {
   constructor(db, username, password, options) {
@@ -29,7 +30,7 @@ class AddUserOperation extends CommandOperation {
     // If not roles defined print deprecated message
     // TODO: handle deprecation properly
     if (roles.length === 0) {
-      console.log('Creating a user without roles is deprecated in MongoDB >= 2.6');
+      emitWarning('Creating a user without roles is deprecated in MongoDB >= 2.6');
     }
 
     // Check the db name and add roles if needed

lib/operations/connect.js

@@ -13,6 +13,7 @@ const ReplSet = require('../topologies/replset');
 const Server = require('../topologies/server');
 const ServerSessionPool = require('../core').Sessions.ServerSessionPool;
 const emitDeprecationWarning = require('../utils').emitDeprecationWarning;
+const emitWarningOnce = require('../utils').emitWarningOnce;
 const fs = require('fs');
 const WriteConcern = require('../write_concern');
 const BSON = require('../core/connection/utils').retrieveBSON();
@@ -182,12 +183,12 @@ function validOptions(options) {
       if (options.validateOptions) {
         return new MongoError(`option ${name} is not supported`);
       } else {
-        console.warn(`the options [${name}] is not supported`);
+        emitWarningOnce(`the options [${name}] is not supported`);
       }
     }
 
     if (legacyOptionNames.indexOf(name) !== -1) {
-      console.warn(
+      emitWarningOnce(
         `the server/replset/mongos/db options are deprecated, ` +
           `all their options are supported at the top level of the options object [${validOptionNames}]`
       );
@@ -257,9 +258,6 @@ function resolveTLSOptions(options) {
   });
 }
 
-const emitDeprecationForNonUnifiedTopology = deprecate(() => {},
-'current Server Discovery and Monitoring engine is deprecated, and will be removed in a future version. ' + 'To use the new Server Discover and Monitoring engine, pass option { useUnifiedTopology: true } to the MongoClient constructor.');
-
 function connect(mongoClient, url, options, callback) {
   options = Object.assign({}, options);
 
@@ -335,7 +333,9 @@ function connect(mongoClient, url, options, callback) {
       return createTopology(mongoClient, 'unified', _finalOptions, connectCallback);
     }
 
-    emitDeprecationForNonUnifiedTopology();
+    emitWarningOnce(
+      'Current Server Discovery and Monitoring engine is deprecated, and will be removed in a future version. To use the new Server Discover and Monitoring engine, pass option { useUnifiedTopology: true } to the MongoClient constructor.'
+    );
 
     // Do we have a replicaset then skip discovery and go straight to connectivity
     if (_finalOptions.replicaSet || _finalOptions.rs_name) {

lib/utils.js

@@ -534,7 +534,9 @@ function decorateWithExplain(command, explain) {
   return { explain: command, verbosity: explain.verbosity };
 }
 
-const emitProcessWarning = msg => process.emitWarning(msg, 'DeprecationWarning');
+const emitProcessWarning = msg =>
+  process.emitWarning(msg, { type: 'DeprecationWarning', code: MONGODB_WARNING_CODE });
+// eslint-disable-next-line no-console
 const emitConsoleWarning = msg => console.error(msg);
 const emitDeprecationWarning = process.emitWarning ? emitProcessWarning : emitConsoleWarning;
 
@@ -816,6 +818,48 @@ function hasAtomicOperators(doc) {
   );
 }
 
+/**
+ * When the driver used emitWarning the code will be equal to this.
+ * @public
+ *
+ * @example
+ * ```js
+ * process.on('warning', (warning) => {
+ *  if (warning.code === MONGODB_WARNING_CODE) console.error('Ah an important warning! :)')
+ * })
+ * ```
+ */
+const MONGODB_WARNING_CODE = 'MONGODB DRIVER';
+
+/**
+ * @internal
+ * @param {string} message - message to warn about
+ */
+function emitWarning(message) {
+  if (process.emitWarning) {
+    return process.emitWarning(message, { code: MONGODB_WARNING_CODE });
+  } else {
+    // Approximate the style of print out on node versions pre 8.x
+    // eslint-disable-next-line no-console
+    return console.error(`[${MONGODB_WARNING_CODE}] Warning:`, message);
+  }
+}
+
+const emittedWarnings = new Set();
+/**
+ * Will emit a warning once for the duration of the application.
+ * Uses the message to identify if it has already been emitted
+ * so using string interpolation can cause multiple emits
+ * @internal
+ * @param {string} message - message to warn about
+ */
+function emitWarningOnce(message) {
+  if (!emittedWarnings.has(message)) {
+    emittedWarnings.add(message);
+    return emitWarning(message);
+  }
+}
+
 module.exports = {
   filterOptions,
   mergeOptions,
@@ -849,5 +893,8 @@ module.exports = {
   now,
   calculateDurationInMs,
   makeInterruptableAsyncInterval,
-  hasAtomicOperators
+  hasAtomicOperators,
+  MONGODB_WARNING_CODE,
+  emitWarning,
+  emitWarningOnce
 };

lib/write_concern.js

@@ -1,6 +1,7 @@
 'use strict';
 
 const kWriteConcernKeys = new Set(['w', 'wtimeout', 'j', 'journal', 'fsync']);
+let utils;
 
 /**
  * The **WriteConcern** class is a class that represents a MongoDB WriteConcern.
@@ -75,7 +76,10 @@ class WriteConcern {
       );
     }
 
-    console.warn(
+    // this is down here to prevent circular dependency
+    if (!utils) utils = require('./utils');
+
+    utils.emitWarningOnce(
       `Top-level use of w, wtimeout, j, and fsync is deprecated. Use writeConcern instead.`
     );
     return new WriteConcern(

test/.eslintrc.json

@@ -0,0 +1,6 @@
+{
+  "extends": "../.eslintrc.json",
+  "rules": {
+    "no-console": "off"
+  }
+}

test/unit/sdam/server_selection/select_servers.test.js

@@ -85,7 +85,6 @@ describe('selectServer', function() {
       let completed = 0;
       function finish() {
         completed++;
-        console.log(completed);
         if (completed === toSelect) done();
       }