eslint: Fix no-useless-concat.

https://eslint.org/docs/rules/no-useless-concat

And add some escaping to static/js/markdown.js while I’m here.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

.eslintrc.json

@@ -85,6 +85,7 @@
             }
         ],
         "no-use-before-define": ["error", {"functions": false}],
+        "no-useless-concat": "error",
         "no-useless-constructor": "error",
         "no-var": "error",
         "object-shorthand": "error",

frontend_tests/node_tests/compose.js

@@ -690,7 +690,7 @@ run_test("send_message", () => {
 
         // Setting message content with a host server link and we will assert
         // later that this has been converted to a relative link.
-        $("#compose-textarea").val("[foobar]" + "(https://foo.com/user_uploads/123456)");
+        $("#compose-textarea").val("[foobar](https://foo.com/user_uploads/123456)");
         $("#compose-textarea").trigger("blur");
         $("#compose-send-status").show();
         $("#compose-send-button").prop("disabled", true);

frontend_tests/node_tests/list_render.js

@@ -223,7 +223,7 @@ run_test("filtering", () => {
     const new_data = ["greta", "faye", "gary", "frank", "giraffe", "fox"];
 
     widget.replace_list_data(new_data);
-    expected_html = "<div>greta</div>" + "<div>gary</div>" + "<div>giraffe</div>";
+    expected_html = "<div>greta</div><div>gary</div><div>giraffe</div>";
     assert.deepEqual(container.appended_data.html(), expected_html);
 });
 
@@ -240,7 +240,7 @@ run_test("no filtering", () => {
     const widget = list_render.create(container, ["apple", "banana"], opts);
     widget.render();
 
-    const expected_html = "<div>apple</div>" + "<div>banana</div>";
+    const expected_html = "<div>apple</div><div>banana</div>";
     assert.deepEqual(container.appended_data.html(), expected_html);
 });
 

frontend_tests/node_tests/markdown.js

@@ -364,12 +364,12 @@ run_test("marked", () => {
         {
             input: "This is a #**Denmark>some topic** stream_topic link",
             expected:
-                '<p>This is a <a class="stream-topic" data-stream-id="1" href="/#narrow/stream/1-Denmark/topic/some.20topic">#Denmark > some topic</a> stream_topic link</p>',
+                '<p>This is a <a class="stream-topic" data-stream-id="1" href="/#narrow/stream/1-Denmark/topic/some.20topic">#Denmark &gt; some topic</a> stream_topic link</p>',
         },
         {
             input: "This has two links: #**Denmark>some topic** and #**social>other topic**.",
             expected:
-                '<p>This has two links: <a class="stream-topic" data-stream-id="1" href="/#narrow/stream/1-Denmark/topic/some.20topic">#Denmark > some topic</a> and <a class="stream-topic" data-stream-id="2" href="/#narrow/stream/2-social/topic/other.20topic">#social > other topic</a>.</p>',
+                '<p>This has two links: <a class="stream-topic" data-stream-id="1" href="/#narrow/stream/1-Denmark/topic/some.20topic">#Denmark &gt; some topic</a> and <a class="stream-topic" data-stream-id="2" href="/#narrow/stream/2-social/topic/other.20topic">#social &gt; other topic</a>.</p>',
         },
         {
             input: "This is not a #**Denmark>** stream_topic link",
@@ -512,7 +512,7 @@ run_test("marked", () => {
         {
             input: "#**Bobby <h1>Tables</h1>**",
             expected:
-                '<p><a class="stream-topic" data-stream-id="4" href="/#narrow/stream/4-Bobby-.3Ch1/topic/Tables.3C.2Fh1.3E">#Bobby &lt;h1 > Tables&lt;/h1&gt;</a></p>',
+                '<p><a class="stream-topic" data-stream-id="4" href="/#narrow/stream/4-Bobby-.3Ch1/topic/Tables.3C.2Fh1.3E">#Bobby &lt;h1 &gt; Tables&lt;/h1&gt;</a></p>',
         },
         {
             input: "#**& &amp; &amp;amp;**",
@@ -522,7 +522,7 @@ run_test("marked", () => {
         {
             input: "#**& &amp; &amp;amp;>& &amp; &amp;amp;**",
             expected:
-                '<p><a class="stream-topic" data-stream-id="5" href="/#narrow/stream/5-.26-.26.20.26amp.3B/topic/.26.20.26.20.26amp.3B">#&amp; &amp; &amp;amp; > &amp; &amp; &amp;amp;</a></p>',
+                '<p><a class="stream-topic" data-stream-id="5" href="/#narrow/stream/5-.26-.26.20.26amp.3B/topic/.26.20.26.20.26amp.3B">#&amp; &amp; &amp;amp; &gt; &amp; &amp; &amp;amp;</a></p>',
         },
     ];
 

frontend_tests/node_tests/people.js

@@ -885,7 +885,7 @@ run_test("updates", () => {
     // old email.
     blueslip.expect(
         "warn",
-        "Obsolete email passed to get_by_email: " + "FOO@example.com new email = bar@example.com",
+        "Obsolete email passed to get_by_email: FOO@example.com new email = bar@example.com",
     );
     person = people.get_by_email(old_email);
     assert.equal(person.user_id, user_id);

frontend_tests/node_tests/vdom.js

@@ -15,10 +15,7 @@ run_test("basics", () => {
 
     const html = vdom.render_tag(ul);
 
-    assert.equal(
-        html,
-        '<ul class="foo" title="cats &amp; &lt;&quot;dogs&quot;&gt;">\n\n' + "</ul>",
-    );
+    assert.equal(html, '<ul class="foo" title="cats &amp; &lt;&quot;dogs&quot;&gt;">\n\n</ul>');
 });
 
 run_test("attribute escaping", () => {
@@ -59,7 +56,7 @@ run_test("attribute updates", () => {
 
     const html = vdom.render_tag(ul);
 
-    assert.equal(html, '<ul class="same" color="blue" id="101">\n\n' + "</ul>");
+    assert.equal(html, '<ul class="same" color="blue" id="101">\n\n</ul>');
 
     let updated;
     let removed;
@@ -135,10 +132,7 @@ run_test("children", () => {
 
     vdom.update(replace_content, find, ul);
 
-    assert.equal(
-        rendered_html,
-        "<ul>\n" + "<li>foo1</li>\n" + "<li>foo2</li>\n" + "<li>foo3</li>\n" + "</ul>",
-    );
+    assert.equal(rendered_html, "<ul>\n<li>foo1</li>\n<li>foo2</li>\n<li>foo3</li>\n</ul>");
 
     // Force a complete redraw.
     const new_nodes = make_children([4, 5]);
@@ -150,10 +144,7 @@ run_test("children", () => {
     const new_ul = vdom.ul(new_opts);
     vdom.update(replace_content, find, new_ul, ul);
 
-    assert.equal(
-        rendered_html,
-        '<ul class="main">\n' + "<li>foo4</li>\n" + "<li>foo5</li>\n" + "</ul>",
-    );
+    assert.equal(rendered_html, '<ul class="main">\n<li>foo4</li>\n<li>foo5</li>\n</ul>');
 });
 
 run_test("partial updates", () => {
@@ -176,10 +167,7 @@ run_test("partial updates", () => {
 
     vdom.update(replace_content, find, ul);
 
-    assert.equal(
-        rendered_html,
-        "<ul>\n" + "<li>foo1</li>\n" + "<li>foo2</li>\n" + "<li>foo3</li>\n" + "</ul>",
-    );
+    assert.equal(rendered_html, "<ul>\n<li>foo1</li>\n<li>foo2</li>\n<li>foo3</li>\n</ul>");
 
     replace_content = () => {
         throw new Error("should not replace entire html");

static/js/alert_words.js

@@ -37,10 +37,7 @@ exports.process_message = function (message) {
         const before_punctuation = "\\s|^|>|[\\(\\\".,';\\[]";
         const after_punctuation = "\\s|$|<|[\\)\\\"\\?!:.,';\\]!]";
 
-        const regex = new RegExp(
-            "(" + before_punctuation + ")" + "(" + clean + ")" + "(" + after_punctuation + ")",
-            "ig",
-        );
+        const regex = new RegExp(`(${before_punctuation})(${clean})(${after_punctuation})`, "ig");
         message.content = message.content.replace(
             regex,
             (match, before, word, after, offset, content) => {

static/js/blueslip.js

@@ -155,7 +155,7 @@ function report_error(msg, stack, opts) {
         error() {
             if (opts.show_ui_msg && ui_report !== undefined) {
                 ui_report.message(
-                    "Oops.  It seems something has gone wrong. " + "Please try reloading the page.",
+                    "Oops.  It seems something has gone wrong. Please try reloading the page.",
                     $("#home-error"),
                     "alert-error",
                 );

static/js/hash_util.js

@@ -166,7 +166,7 @@ exports.by_conversation_and_time_uri = function (message) {
 };
 
 exports.stream_edit_uri = function (sub) {
-    const hash = "#streams" + "/" + sub.stream_id + "/" + exports.encodeHashComponent(sub.name);
+    const hash = `#streams/${sub.stream_id}/${exports.encodeHashComponent(sub.name)}`;
     return hash;
 };
 

static/js/markdown.js

@@ -102,7 +102,7 @@ exports.apply_markdown = function (message) {
         userMentionHandler(mention, silently) {
             if (mention === "all" || mention === "everyone" || mention === "stream") {
                 message.mentioned = true;
-                return '<span class="user-mention" data-user-id="*">' + "@" + mention + "</span>";
+                return `<span class="user-mention" data-user-id="*">@${_.escape(mention)}</span>`;
             }
 
             let full_name;
@@ -160,15 +160,15 @@ exports.apply_markdown = function (message) {
             }
             let str = "";
             if (silently) {
-                str += '<span class="user-mention silent" data-user-id="' + user_id + '">';
+                str += `<span class="user-mention silent" data-user-id="${_.escape(user_id)}">`;
             } else {
-                str += '<span class="user-mention" data-user-id="' + user_id + '">@';
+                str += `<span class="user-mention" data-user-id="${_.escape(user_id)}">@`;
             }
 
             // If I mention "@aLiCe sMITH", I still want "Alice Smith" to
             // show in the pill.
             const actual_full_name = helpers.get_actual_name_from_user_id(user_id);
-            return str + _.escape(actual_full_name) + "</span>";
+            return `${str}${_.escape(actual_full_name)}</span>`;
         },
         groupMentionHandler(name) {
             const group = helpers.get_user_group_from_name(name);
@@ -176,14 +176,9 @@ exports.apply_markdown = function (message) {
                 if (helpers.is_member_of_user_group(group.id, helpers.my_user_id())) {
                     message.mentioned = true;
                 }
-                return (
-                    '<span class="user-group-mention" data-user-group-id="' +
-                    group.id +
-                    '">' +
-                    "@" +
-                    _.escape(group.name) +
-                    "</span>"
-                );
+                return `<span class="user-group-mention" data-user-group-id="${_.escape(
+                    group.id,
+                )}">@${_.escape(group.name)}</span>`;
             }
             return undefined;
         },
@@ -251,19 +246,9 @@ exports.is_status_message = function (raw_content) {
 };
 
 function make_emoji_span(codepoint, title, alt_text) {
-    return (
-        '<span aria-label="' +
-        title +
-        '"' +
-        ' class="emoji emoji-' +
-        codepoint +
-        '"' +
-        ' role="img" title="' +
-        title +
-        '">' +
-        alt_text +
-        "</span>"
-    );
+    return `<span aria-label="${_.escape(title)}" class="emoji emoji-${_.escape(
+        codepoint,
+    )}" role="img" title="${_.escape(title)}">${_.escape(alt_text)}</span>`;
 }
 
 function handleUnicodeEmoji(unicode_emoji) {
@@ -293,17 +278,9 @@ function handleEmoji(emoji_name) {
     const emoji_url = emoji.get_realm_emoji_url(emoji_name);
 
     if (emoji_url) {
-        return (
-            '<img alt="' +
-            alt_text +
-            '"' +
-            ' class="emoji" src="' +
-            emoji_url +
-            '"' +
-            ' title="' +
-            title +
-            '">'
-        );
+        return `<img alt="${_.escape(alt_text)}" class="emoji" src="${_.escape(
+            emoji_url,
+        )}" title="${_.escape(title)}">`;
     }
 
     const codepoint = emoji.get_emoji_codepoint(emoji_name);
@@ -350,18 +327,9 @@ function handleStream(stream_name) {
         return undefined;
     }
     const href = helpers.stream_hash(stream.stream_id);
-    return (
-        '<a class="stream" data-stream-id="' +
-        stream.stream_id +
-        '" ' +
-        'href="/' +
-        href +
-        '"' +
-        ">" +
-        "#" +
-        _.escape(stream.name) +
-        "</a>"
-    );
+    return `<a class="stream" data-stream-id="${_.escape(stream.stream_id)}" href="/${_.escape(
+        href,
+    )}">#${_.escape(stream.name)}</a>`;
 }
 
 function handleStreamTopic(stream_name, topic) {
@@ -370,18 +338,10 @@ function handleStreamTopic(stream_name, topic) {
         return undefined;
     }
     const href = helpers.stream_topic_hash(stream.stream_id, topic);
-    const text = "#" + _.escape(stream.name) + " > " + _.escape(topic);
-    return (
-        '<a class="stream-topic" data-stream-id="' +
-        stream.stream_id +
-        '" ' +
-        'href="/' +
-        href +
-        '"' +
-        ">" +
-        text +
-        "</a>"
-    );
+    const text = `#${stream.name} > ${topic}`;
+    return `<a class="stream-topic" data-stream-id="${_.escape(
+        stream.stream_id,
+    )}" href="/${_.escape(href)}">${_.escape(text)}</a>`;
 }
 
 function handleRealmFilter(pattern, matches) {
@@ -404,7 +364,7 @@ function handleTex(tex, fullmatch) {
     } catch (error) {
         if (error.message.startsWith("KaTeX parse error")) {
             // TeX syntax error
-            return '<span class="tex-error">' + _.escape(fullmatch) + "</span>";
+            return `<span class="tex-error">${_.escape(fullmatch)}</span>`;
         }
         blueslip.error(error);
         return undefined;

static/js/portico/integrations_dev_panel.js

@@ -188,7 +188,7 @@ function handle_unsuccessful_response(response) {
     try {
         const status_code = response.statusCode().status;
         response = JSON.parse(response.responseText);
-        set_results_notice("Result: " + "(" + status_code + ") " + response.msg, "warning");
+        set_results_notice(`Result: (${status_code}) ${response.msg}`, "warning");
     } catch {
         // If the response is not a JSON response, then it is probably
         // Django returning an HTML response containing a stack trace

static/js/sent_messages.js

@@ -73,7 +73,7 @@ class MessageState {
         }
 
         blueslip.log(
-            "Restarting get_events due to " + "delayed receipt of sent message " + this.local_id,
+            `Restarting get_events due to delayed receipt of sent message ${this.local_id}`,
         );
 
         server_events.restart_get_events();

static/js/settings_streams.js

@@ -81,7 +81,7 @@ function make_stream_default(stream_id) {
 
 exports.delete_default_stream = function (stream_id, default_stream_row, alert_element) {
     channel.del({
-        url: "/json/default_streams" + "?" + $.param({stream_id}),
+        url: "/json/default_streams?" + $.param({stream_id}),
         error(xhr) {
             ui_report.generic_row_button_error(xhr, alert_element);
         },