[FIX] qweb2: ignore comments between branching directives

Have a template of that form:
```xml
<t t-if=""/>
<!-- Comment -->
<t t-elif=""/>
```

Before this commit, both python and JS crashed because any type of node
between branching directive was forbidden

After this commit, Comments are just ignored and removed, while actual
template nodes are still forbidden between branching directives
There is no crash anymore

closes odoo/odoo#45899

Signed-off-by: Lucas Perais (lpe) <lpe@odoo.com>

2 files changed, 28 insertions, 1 deletions

diff --git a/addons/web/static/lib/qweb/qweb-test-conditionals.xml b/addons/web/static/lib/qweb/qweb-test-conditionals.xml
index e754298a4aa..f4b95b697da 100644
--- a/addons/web/static/lib/qweb/qweb-test-conditionals.xml
+++ b/addons/web/static/lib/qweb/qweb-test-conditionals.xml
@@ -38,4 +38,31 @@
     </t>
     <params id="boolean-value-condition-false-else">{"condition": false}</params>
     <result id="boolean-value-condition-false-else"><![CDATA[<div><span>begin</span>fail-else<span>end</span></div>]]></result>
+
+    <t t-name="comment-branching">
+        <t t-if="condition == 'if'">if</t>
+        <t t-elif="condition == 'elif1'">elif1</t>
+        <!-- Comment ignored PART OF THE TEST !!!  -->
+        <t t-elif="condition == 'elif2'">elif2</t>
+        <t t-else="">else</t>
+    </t>
+    <params id="comment-branching">{"condition": "elif1"}</params>
+    <result id="comment-branching"><![CDATA[elif1]]></result>
+
+    <t t-name="comment-branching-1">
+        <t t-if="condition == 'if'">if</t>
+        <t t-elif="condition == 'elif1'">elif1</t>
+        <!-- Comment ignored PART OF THE TEST !!!  -->
+        <t t-elif="condition == 'elif2'">elif2</t>
+        <t t-else="">else</t>
+    </t>
+    <params id="comment-branching-1">{"condition": "elif2"}</params>
+    <result id="comment-branching-1"><![CDATA[elif2]]></result>
+
+    <t t-name="comment-branching-2">
+        <div t-if="condition == 'if'">if</div><!-- Comment ignored PART OF THE TEST !!!  --><div>sometext</div>
+    </t>
+    <params id="comment-branching-2">{"condition": "if"}</params>
+    <result id="comment-branching-2"><![CDATA[<div>if</div><div>sometext</div>]]></result>
+
 </templates>
diff --git a/addons/web/static/lib/qweb/qweb2.js b/addons/web/static/lib/qweb/qweb2.js
index 5126138bc36..2cfd2286cbc 100644
--- a/addons/web/static/lib/qweb/qweb2.js
+++ b/addons/web/static/lib/qweb/qweb2.js
@@ -327,7 +327,7 @@ QWeb2.Engine = (function() {
                     // All text nodes between branch nodes are removed
                     var text_node;
                     while ((text_node = node.previousSibling) !== prev_elem) {
-                        if (self.tools.trim(text_node.nodeValue)) {
+                        if (text_node.nodeType !== 8 && self.tools.trim(text_node.nodeValue)) {
                             return self.tools.exception("Error: text is not allowed between branching directives");
                         }
                         // IE <= 11.0 doesn't support ChildNode.remove