templates: Fix minor whitespace errors.

(we also add validation)

static/templates/settings/playground_settings_admin.hbs

@@ -18,7 +18,7 @@
         </p>
         <ul>
             <li><code>Python</code> {{t "and" }} <code>https://replit.com/languages/python3/?code=</code></li>
-            <li><code>JavaScript</code>  {{t "and" }} <code>https://replit.com/languages/javascript/?code=</code></li>
+            <li><code>JavaScript</code> {{t "and" }} <code>https://replit.com/languages/javascript/?code=</code></li>
         </ul>
 
         {{#if is_admin}}

templates/corporate/jobs.html

@@ -49,7 +49,7 @@
                     How we work
                 </h1>
                 <p>
-                    <strong>Open source.</strong>  The Zulip software is 100% free and
+                    <strong>Open source.</strong> The Zulip software is 100% free and
                     open source.  We're <a href="/team/">an open-source project</a> first,
                     and we’re building a sustainable business as a means to support the
                     project's growth and long-term future. We provide the same open-source
@@ -77,7 +77,7 @@
                     are open to all applicants without regard for location.
                 </p>
                 <p>
-                    <strong>Maintainable software.</strong>  Great
+                    <strong>Maintainable software.</strong> Great
                     software over time depends on a team’s shared
                     understanding of a system and how to change it, as
                     much as on the code itself. Beyond writing our

templates/corporate/upgrade.html

@@ -49,7 +49,7 @@
                                 <input type="hidden" name="onboarding" value="true" />
                                 {% endif %}
                                 {% if onboarding and free_trial_days %}
-                                <p><b>Not ready to start your trial?</b>  <a href="/">Continue with the Zulip Cloud Free plan</a>.</p>
+                                <p><b>Not ready to start your trial?</b> <a href="/">Continue with the Zulip Cloud Free plan</a>.</p>
                                 <hr />
                                 <h2>Zulip Standard free trial</h2>
                                 {% endif %}
@@ -165,7 +165,7 @@
                         <div id="invoice-input-section">
                             <form id="invoice-form" method="post">
                                 {% if onboarding and free_trial_days %}
-                                <p><b>Not ready to start your trial?</b>  <a href="/">Continue with the Zulip Cloud Free plan</a>.</p>
+                                <p><b>Not ready to start your trial?</b> <a href="/">Continue with the Zulip Cloud Free plan</a>.</p>
                                 <hr />
                                 <h2>Zulip Standard free trial</h2>
                                 {% endif %}

templates/zerver/development/integrations_dev_panel.html

@@ -70,7 +70,7 @@
     <br />
 
     <div class="row2">
-        <label for="URL"><b>URL</b>  (automatically generated)</label>
+        <label for="URL"><b>URL</b> (automatically generated)</label>
         <input id="URL" type="text" />
     </div>
 

templates/zerver/emails/confirm_new_email.source.html

@@ -10,5 +10,5 @@
 <p>{% trans realm_uri=macros.link_tag(realm_uri), old_email=macros.email_tag(old_email), new_email=macros.email_tag(new_email) %}We received a request to change the email address for the Zulip account on {{ realm_uri }} from {{ old_email }} to {{ new_email }}. To confirm this change, please click below:{% endtrans %}
 <a class="button" href="{{ activate_url }}">{{_('Confirm email change') }}</a></p>
 
-<p>{% trans support_email=macros.email_tag(support_email) %}If you did not request this change, please contact us immediately at  {{ support_email }}.{% endtrans %}</p>
+<p>{% trans support_email=macros.email_tag(support_email) %}If you did not request this change, please contact us immediately at {{ support_email }}.{% endtrans %}</p>
 {% endblock %}

templates/zerver/login.html

@@ -135,7 +135,7 @@ page can be easily identified in it's respective JavaScript file. -->
                         <form class="social_login_form form-inline" action="{{ backend.login_url }}" method="get">
                             <input type="hidden" name="next" value="{{ next }}" />
                             <button id="login_{{ backend.button_id_suffix }}" class="login-social-button"
-                              {% if backend.display_icon %} style="background-image:url({{ backend.display_icon }})"  {% endif %}>                                {{ _('Log in with %(identity_provider)s', identity_provider=backend.display_name) }}
+                              {% if backend.display_icon %} style="background-image:url({{ backend.display_icon }})"  {% endif %}> {{ _('Log in with %(identity_provider)s', identity_provider=backend.display_name) }}
                             </button>
                         </form>
                     </div>

tools/lib/template_parser.py

@@ -290,6 +290,7 @@ def validate(fn: Optional[str] = None, text: Optional[str] = None) -> None:
             {e}"""
         )
 
+    prevent_whitespace_violations(fn, tokens)
     prevent_dangling_tags(fn, tokens)
 
     class State:
@@ -435,6 +436,38 @@ def validate(fn: Optional[str] = None, text: Optional[str] = None) -> None:
         raise TemplateParserException("Missing end tag")
 
 
+def prevent_whitespace_violations(fn: str, tokens: List[Token]) -> None:
+    if tokens[0].kind in ("indent", "whitespace"):
+        raise TemplateParserException(f" Please remove the whitespace at the beginning of {fn}.")
+
+    for i in range(1, len(tokens) - 1):
+        token = tokens[i]
+        next_token = tokens[i + 1]
+
+        if token.kind == "indent":
+            if next_token.kind in ("indent", "whitespace"):
+                raise AssertionError("programming error parsing indents")
+
+            if next_token.kind == "newline":
+                raise TemplateParserException(
+                    f"""Please just make row {token.line} in {fn} a truly blank line (no spaces)."""
+                )
+
+        if token.kind == "whitespace":
+            if len(token.s) > 1:
+                raise TemplateParserException(
+                    f"""
+                        We did not expect this much whitespace at row {token.line} column {token.col} in {fn}.
+                    """
+                )
+            if next_token.kind == "newline":
+                raise TemplateParserException(
+                    f"""
+                        Unexpected trailing whitespace at row {token.line} column {token.col} in {fn}.
+                    """
+                )
+
+
 def prevent_dangling_tags(fn: str, tokens: List[Token]) -> None:
     """
     Prevent this kind of HTML: