Comment syntax and strange partial rendering

Rails
1

Using rails 2.3.2 I have a partial _foo.rhtml that begins with a comment
as follows:

<% # here is a comment %>
<li><%= foo %></li>

When I render the partial from a view in the traditional way, e.g.

<% some_numbers = [1, 2, 3, 4, 5] %>
<ul>
<%= render :partial => "foo", :collection => some_numbers %>
</ul>

I found that the

  • and
    • tags are not rendered. However, I can
    solve this problem by fixing _foo.rhtml to eliminate the space between
    <% and # so that it reads: 
    <%# here is a comment %>
<li><%= foo %></li>

    My question: what’s going on here? E.g., is <% # comment %> simply
    incorrect syntax for including comments in a template? Or is the
    problem more subtle?

    Thanks!

    2

    2010/1/18 Benjamin R. [email protected]:

    Â Â <%= render :partial => “foo”, :collection => some_numbers %>
    incorrect syntax for including comments in a template? Â Or is the
    problem more subtle?

    <% # is invalid syntax, the only comment syntax allowed in erb is <%#

    Unfortunately using <% # does not necessarily give a syntax error,
    just unexpected results.

    Colin

    3

    Colin L. wrote:

    …
    <% # is invalid syntax, the only comment syntax allowed in erb is <%#

    It is not actually invalid. Just the rest of the line is considered as
    comment including %>. Working (though ugly) code was:

    <% # here is a comment
    %>

    T.

    4

    2010/1/18 T.N. T. [email protected]:

    Colin L. wrote:

    …
    <% # is invalid syntax, the only comment syntax allowed in erb is <%#

    It is not actually invalid. Just the rest of the line is considered as
    comment including %>. Working (though ugly) code was:

    <% # here is a comment
    %>

    It may work but I am not sure it is valid erb syntax. In a previous
    version of Rails <% # comment %> worked. I am not sure that
    <% # here is a comment
    %>
    can be guaranteed to work in the future. I may be wrong though.

    Colin

    5

    Colin L. wrote:

    It may work but I am not sure it is valid erb syntax. In a previous
    version of Rails <% # comment %> worked. I am not sure that
    <% # here is a comment
    %>
    can be guaranteed to work in the future. I may be wrong though.

    Your probably right. And there really should be at least a warning when
    it is found in a template.

    6

    T. N. T. wrote:

    Colin L. wrote:

    It may work but I am not sure it is valid erb syntax. In a previous
    version of Rails <% # comment %> worked. I am not sure that
    <% # here is a comment
    %>
    can be guaranteed to work in the future. I may be wrong though.

    Your probably right. And there really should be at least a warning when
    it is found in a template.

    Wow! Add this weirdness to the list of reasons to use Haml rather than
    ERb (as if I needed more reasons… :slight_smile: ).

    Best,
    –Â
    Marnen Laibow-Koser
    http://www.marnen.org
    [email protected]

    7

    2010/1/18 Marnen Laibow-Koser [email protected]:

    …

    Wow! Â Add this weirdness to the list of reasons to use Haml rather than
    ERb (as if I needed more reasons… :slight_smile: ).

    I am with you on that one Marnen. I tried haml a little while ago and
    was immediately hooked. I would highly recommend anyone who has not
    tried it to have a go.

    Colin

    8

    Ah, this makes a lot of sense…thanks everyone!

    -Ben

    PS If content-free thank-yous isn’t appropriate ettiquette, please let
    me know :slight_smile:

    9

    The result is pretty much expected.

    Since you started the general Ruby code block, the closing “%>” is now
    the part of the comment and doesn’t denote the code block end any
    more. To see the difference, try:

    <%

    Comment

    %>

    • Aleksey