node tests: Add nice diffs to js markdown tests.

Fix #3915

frontend_tests/zjsunit/bugdown_assert.js

@@ -23,6 +23,8 @@
 const jsdom = require('jsdom');
 const _ = require('underscore');
 
+const mdiff = require('./mdiff.js');
+
 // Module-level global instance of MarkdownComparer, initialized when needed
 let _markdownComparerInstance = null;
 
@@ -155,25 +157,28 @@ class MarkdownComparer {
     }
 }
 
+function returnComparer() {
+    if (!_markdownComparerInstance) {
+        _markdownComparerInstance = new MarkdownComparer((actual, expected) => {
+            return [
+                "Actual and expected output do not match.  Showing diff",
+                mdiff.diff_strings(actual, expected),
+            ].join('\n');
+        });
+    }
+    return _markdownComparerInstance;
+}
+
 module.exports = {
     equal(expected, actual, message) {
-        if (!_markdownComparerInstance) {
-            _markdownComparerInstance = new MarkdownComparer();
-        }
-        _markdownComparerInstance.assertEqual(actual, expected, message);
+        returnComparer().assertEqual(actual, expected, message);
     },
 
     notEqual(expected, actual, message) {
-        if (!_markdownComparerInstance) {
-            _markdownComparerInstance = new MarkdownComparer();
-        }
-        _markdownComparerInstance.assertNotEqual(actual, expected, message);
+        returnComparer().assertNotEqual(actual, expected, message);
     },
 
     setFormatter(output_formatter) {
-        if (!_markdownComparerInstance) {
-            _markdownComparerInstance = new MarkdownComparer();
-        }
-        _markdownComparerInstance.setFormatter(output_formatter);
+        returnComparer().setFormatter(output_formatter);
     },
 };

frontend_tests/zjsunit/mdiff.js

@@ -0,0 +1,146 @@
+/**
+ * mdiff.js
+ *
+ * Used to produce colorful and informative diffs for comparison of generated
+ * Markdown.  Unlike the built-in diffs used in python or node.js assert libraries,
+ * is actually designed to be effective for long, single-line comparisons.
+ *
+ * Based on diffing library difflib, a js port of the python library.
+ *
+ * The sole exported function diff_strings(string_0, string_1) returns a pretty-printed
+ * unicode string containing their diff.
+ */
+
+const _ = require('underscore');
+const difflib = require('difflib');
+
+function apply_color(input_string, changes) {
+    let previous_index = 0;
+    let processed_string = input_string.slice(0,2);
+    input_string = input_string.slice(2);
+
+    const formatter = {
+        delete : (string) => { return "\u001b[31m" + string + "\u001b[0m"; },
+        insert : (string) => { return "\u001b[32m" + string + "\u001b[0m"; },
+        replace : (string) => { return "\u001b[33m" + string + "\u001b[0m"; },
+    };
+    changes.forEach((change) => {
+        if (formatter.hasOwnProperty(change.tag)) {
+            processed_string += input_string.slice(previous_index, change.beginning_index);
+            processed_string += formatter[change.tag](
+                input_string.slice(change.beginning_index, change.ending_index)
+            );
+            previous_index = change.ending_index;
+        }
+    });
+
+    processed_string += input_string.slice(previous_index);
+    return processed_string;
+}
+
+/**
+ * The library difflib produces diffs that look as follows:
+ *
+ * - <p>upgrade! yes</p>
+ * ?    ^^     -
+ * + <p>downgrade yes.</p>
+ * ?    ^^^^         +
+ *
+ * The purpose of this function is to facilitate converting these diffs into
+ * colored versions, where the question-mark lines are removed, replaced with
+ * directions to add appropriate color to the lines that they annotate.
+ */
+function parse_questionmark_line(questionmark_line) {
+    let current_sequence = "";  // Either "^", "-", "+", or ""
+    let beginning_index = 0;
+    let index = 0;
+
+    const changes_list = [];
+    const aliases = {
+        "^" : "replace",
+        "+" : "insert",
+        "-" : "delete",
+    };
+    const add_change = () => {
+        if (current_sequence) {
+            changes_list.push({
+                tag : aliases[current_sequence],
+                beginning_index,
+                ending_index : index,
+            });
+            current_sequence = "";
+        }
+    };
+
+    questionmark_line = questionmark_line.slice(2).trimRight("\n");
+
+    for (const character of questionmark_line) {
+        if (aliases.hasOwnProperty(character)) {
+            if (current_sequence !== character) {
+                add_change();
+                current_sequence = character;
+                beginning_index = index;
+            }
+        } else {
+            add_change();
+        }
+        index += 1;
+    }
+
+    // In case we have a "change" involving the last character on a line
+    // e.g. a string such as "? ^^  -- ++++"
+    add_change();
+
+    return changes_list;
+}
+
+function diff_strings(string_0, string_1) {
+    let output_lines = [];
+    let ndiff_output = "";
+    let changes_list = [];
+
+    ndiff_output = difflib.ndiff(string_0.split("\n"), string_1.split("\n"));
+
+    ndiff_output.forEach((line) => {
+        if (line.startsWith("+")) {
+            output_lines.push(line);
+        } else if (line.startsWith("-")) {
+            output_lines.push(line);
+        } else if (line.startsWith("?")) {
+            changes_list = parse_questionmark_line(line);
+            output_lines[output_lines.length - 1] = apply_color(
+                output_lines[output_lines.length -1], changes_list);
+        } else {
+            output_lines.push(line);
+        }
+    });
+
+    const emphasize_codes = (string) => {
+        return "\u001b[34m" + string.slice(0,1) + "\u001b[0m" + string.slice(1);
+    };
+    output_lines = _.map(output_lines, emphasize_codes);
+
+    return output_lines.join("\n");
+}
+
+module.exports = { diff_strings };
+
+// Simple CLI for this module
+// Only run this code if called as a command-line utility
+if (require.main === module) {
+    // First two args are just "node" and "mdiff.js"
+    const argv = require('minimist')(process.argv.slice(2));
+
+    if (_.has(argv, "help")) {
+        console.log(process.argv[0] + " " + process.argv[1] +
+            " [ --help ]" +
+            " string_0" +
+            " string_1" +
+            "\n" +
+            "Where string_0 and string_1 are the strings to be diffed"
+        );
+    }
+
+    const output = diff_strings(argv._[0], argv._[1]);
+    console.log(output);
+}

package.json

@@ -9,6 +9,7 @@
     "@types/webpack": "3.0.13",
     "blueimp-md5": "2.10.0",
     "clipboard": "1.5.16",
+    "difflib": "0.2.4",
     "emoji-datasource": "3.0.0",
     "emoji-datasource-apple": "3.0.0",
     "emoji-datasource-emojione": "3.0.0",

version.py

@@ -1,3 +1,3 @@
 ZULIP_VERSION = "1.7.1+git"
 
-PROVISION_VERSION = '14.1'
+PROVISION_VERSION = '14.2'

yarn.lock

@@ -1207,6 +1207,12 @@ diffie-hellman@^5.0.0:
     miller-rabin "^4.0.0"
     randombytes "^2.0.0"
 
+difflib@^0.2.4:
+  version "0.2.4"
+  resolved "https://registry.yarnpkg.com/difflib/-/difflib-0.2.4.tgz#b5e30361a6db023176d562892db85940a718f47e"
+  dependencies:
+    heap ">= 0.2.0"
+
 doctrine@^1.2.2:
   version "1.5.0"
   resolved "https://registry.yarnpkg.com/doctrine/-/doctrine-1.5.0.tgz#379dce730f6166f76cefa4e6707a159b02c5a6fa"
@@ -2631,6 +2637,10 @@ hawk@~3.1.3:
     hoek "2.x.x"
     sntp "1.x.x"
 
+"heap@>= 0.2.0":
+  version "0.2.6"
+  resolved "https://registry.yarnpkg.com/heap/-/heap-0.2.6.tgz#087e1f10b046932fc8594dd9e6d378afc9d1e5ac"
+
 hmac-drbg@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/hmac-drbg/-/hmac-drbg-1.0.1.tgz#d2745701025a6c775a6c545793ed502fc0c649a1"