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Python template engines and implementation in Indico

This project focuses on upgrading the Indico template system by integrating new Python template engines like Mako and Jinja2, replacing the outdated XSLT. The need for change arises from current system limitations, including high maintenance costs and performance issues. The project outlines the history of Indico templates, evaluates various template engines, and discusses the integration processes. A testing approach compares outputs of the old and new systems to ensure quality. Remaining work includes fine-tuning event styles and improving internationalization support.

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Python template engines and implementation in Indico

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  1. Python template engines and implementation in Indico Marius Damarackas (Vilnius University)

  2. About me • Software engineering student • Doing 3 months long internship in CERN • Improving Indico template system

  3. Outline • History of Indico templates • Why change the current system? • Main tasks • Research about available template systems • Integration of the new engine • Replacing XSLT with normal templates • Remaining work

  4. History of Indico templates • First generation >>>'<div width="100%%">%(param)s</div>'%{'param':'Value'}'<div width="100%>Value</div>'

  5. History of Indico templates • Second generation <% import some.module %> <% foobarList = some.module.createList()%> <table> <%forfooin foobarList: %> <tr> <%iffoo== bar: %> <td><%=foo%></td> <%end%> <%else: %> <td>foobar</td> <%end%> </tr> <%end%> </table>

  6. Why change the current system? • Maintenance costs • Slow when including other templates • No cache • No HTML escaping • Strange usage of the colon symbols: <%latestNews=newsList[:5]%> <% end %>

  7. 1. Research • Some of the candidates • Genshi • Mako • Cheetah • Jinja2

  8. 1. Research • Genshi • Claims to be the fastest XML template engine • Used by Trac • XML and Text versions • Features like caching, XSS protections • Slow • Very difficult to translate Indico templates

  9. 1. Research • Mako • Used by python.org and reddit.com • Very fast: compiles to Python modules • Allows to disable Unicode (a plus for Indico) • Template inheritance mechanism • Syntax could be better, more unified

  10. 1. Research • Jinja2 • Quite fast • Template inheritance • Strong separation of logic and presentation • Difficult to adapt to Indico • Cheetah • Manual compilation to Python modules • Mako does it automatically • Personally I did not like the syntax

  11. 2. Integration • Replace old engine code with TemplateLookup • Problem: more than 800 .tpl files to translate

  12. 2. Integration • Using a script to convert files • Mainly based on regexps • Some things needed to be changed by hand

  13. 2. Testing integration • Basic idea to test the integration: • use *both* old Indico and new Mako templates • Generate outputs and do diff • If there are significant differences, save them • Analyze differences and fix the script

  14. 2. Testing integration • Coverage: 450+ out of 800 templates • 56%, but higher if we count only active files • Allowed to catch some bugs in the script

  15. 3. Replacing XSLT

  16. 3. Replacing XSLT • Generates XML, then applies transformations • Slow • Different from other parts of the system • Lots of code duplication • Difficult to maintain

  17. 3. Replacing XSLT • Maintenance problems … if (chatInfoState]]></xsl:text> <xsl:value-of select="./id" disable-output-escaping="yes"/> <xsl:text disable-output-escaping="yes"><![CDATA[) { IndicoUI.Effect.slide('collaborationInfoLine]]></xsl:text> <xsl:value-of select="./id" disable-output-escaping="yes"/> <xsl:text disable-output-escaping="yes"><![CDATA[', height]]></xsl:text> <xsl:value-of select="./id" disable-output-escaping="yes"/> <xsl:text disable-output-escaping="yes"><![CDATA[); $E('CRMoreInfo]]></xsl:text> <xsl:value-of select="./id" disable-output-escaping="yes"/> <xsl:text disable-output-escaping="yes"><![CDATA[').set('More info'); $E('CRMoreInfo]]></xsl:text> <xsl:value-of select="./id" disable-output-escaping="yes"/> <xsl:text disable-output-escaping="yes"> <![CDATA[').dom.className = "CRDisplayMoreInfo"; …

  18. 3. Replacing XSLT • Same code in human language … if (chatInfoState${id}) { IndicoUI.Effect.slide('collaborationInfoLine${id}', height${id}); $E('CRMoreInfo${id}').set('More info'); $E('CRMoreInfo${id}').dom.className = "CRDisplayMoreInfo"; …

  19. 3. Replacing XSLT • Performance: • Changing the way parameters are passed • No XML • Maintenance: • Most of the styles are similar • Using Mako template inheritance

  20. Remaining work • Think of a smart way to restructure event styles • Fix the i18n script to support the new syntax

  21. Thank you

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