added unit testing, and started implementing unit tests...phew

node_modules/logform/splat.js

@@ -0,0 +1,132 @@
+'use strict';
+
+const util = require('util');
+const { SPLAT } = require('triple-beam');
+
+/**
+ * Captures the number of format (i.e. %s strings) in a given string.
+ * Based on `util.format`, see Node.js source:
+ * https://github.com/nodejs/node/blob/b1c8f15c5f169e021f7c46eb7b219de95fe97603/lib/util.js#L201-L230
+ * @type {RegExp}
+ */
+const formatRegExp = /%[scdjifoO%]/g;
+
+/**
+ * Captures the number of escaped % signs in a format string (i.e. %s strings).
+ * @type {RegExp}
+ */
+const escapedPercent = /%%/g;
+
+class Splatter {
+  constructor(opts) {
+    this.options = opts;
+  }
+
+  /**
+     * Check to see if tokens <= splat.length, assign { splat, meta } into the
+     * `info` accordingly, and write to this instance.
+     *
+     * @param  {Info} info Logform info message.
+     * @param  {String[]} tokens Set of string interpolation tokens.
+     * @returns {Info} Modified info message
+     * @private
+     */
+  _splat(info, tokens) {
+    const msg = info.message;
+    const splat = info[SPLAT] || info.splat || [];
+    const percents = msg.match(escapedPercent);
+    const escapes = percents && percents.length || 0;
+
+    // The expected splat is the number of tokens minus the number of escapes
+    // e.g.
+    // - { expectedSplat: 3 } '%d %s %j'
+    // - { expectedSplat: 5 } '[%s] %d%% %d%% %s %j'
+    //
+    // Any "meta" will be arugments in addition to the expected splat size
+    // regardless of type. e.g.
+    //
+    // logger.log('info', '%d%% %s %j', 100, 'wow', { such: 'js' }, { thisIsMeta: true });
+    // would result in splat of four (4), but only three (3) are expected. Therefore:
+    //
+    // extraSplat = 3 - 4 = -1
+    // metas = [100, 'wow', { such: 'js' }, { thisIsMeta: true }].splice(-1, -1 * -1);
+    // splat = [100, 'wow', { such: 'js' }]
+    const expectedSplat = tokens.length - escapes;
+    const extraSplat = expectedSplat - splat.length;
+    const metas = extraSplat < 0
+      ? splat.splice(extraSplat, -1 * extraSplat)
+      : [];
+
+    // Now that { splat } has been separated from any potential { meta }. we
+    // can assign this to the `info` object and write it to our format stream.
+    // If the additional metas are **NOT** objects or **LACK** enumerable properties
+    // you are going to have a bad time.
+    const metalen = metas.length;
+    if (metalen) {
+      for (let i = 0; i < metalen; i++) {
+        Object.assign(info, metas[i]);
+      }
+    }
+
+    info.message = util.format(msg, ...splat);
+    return info;
+  }
+
+  /**
+    * Transforms the `info` message by using `util.format` to complete
+    * any `info.message` provided it has string interpolation tokens.
+    * If no tokens exist then `info` is immutable.
+    *
+    * @param  {Info} info Logform info message.
+    * @param  {Object} opts Options for this instance.
+    * @returns {Info} Modified info message
+    */
+  transform(info) {
+    const msg = info.message;
+    const splat = info[SPLAT] || info.splat;
+
+    // No need to process anything if splat is undefined
+    if (!splat || !splat.length) {
+      return info;
+    }
+
+    // Extract tokens, if none available default to empty array to
+    // ensure consistancy in expected results
+    const tokens = msg && msg.match && msg.match(formatRegExp);
+
+    // This condition will take care of inputs with info[SPLAT]
+    // but no tokens present
+    if (!tokens && (splat || splat.length)) {
+      const metas = splat.length > 1
+        ? splat.splice(0)
+        : splat;
+
+      // Now that { splat } has been separated from any potential { meta }. we
+      // can assign this to the `info` object and write it to our format stream.
+      // If the additional metas are **NOT** objects or **LACK** enumerable properties
+      // you are going to have a bad time.
+      const metalen = metas.length;
+      if (metalen) {
+        for (let i = 0; i < metalen; i++) {
+          Object.assign(info, metas[i]);
+        }
+      }
+
+      return info;
+    }
+
+    if (tokens) {
+      return this._splat(info, tokens);
+    }
+
+    return info;
+  }
+}
+
+/*
+ * function splat (info)
+ * Returns a new instance of the splat format TransformStream
+ * which performs string interpolation from `info` objects. This was
+ * previously exposed implicitly in `winston < 3.0.0`.
+ */
+module.exports = opts => new Splatter(opts);