.less compilation error when query string is supplied

Question

I have an ASP.Net MVC application which compiles .less files into CSS. In a particular scenario if I hit my endpoint

http:///Account/ResetPassword?t=eyJ0eXAiOiJKV1Qi...

the query string results in a .less compilation warning

directive block with unrecognised format on line 1 in file '~/Content/packageForm.less': []: /beginning of file [1]: @t: eyJ0eXAiOiJKV1Qi...;
^ [2]: @import "setup.less"; directive block with unrecognised format on line 1 in file '~/Content/packageForm.less': []: /beginning of file [1]: @t: eyJ0eXAiOiJKV1Qi...;
^ [2]: @import "setup.less"; directive block with unrecognised format on line 1 in file '~/Content/IE.less': []: /beginning of file [1]: @t: eyJ0eXAiOiJKV1Qi...;
^ [2]: #notes{ directive block with unrecognised format on line 1 in file '~/Content/IE.less': []: /beginning of file [1]: @t: eyJ0eXAiOiJKV1Qi...;
^ [2]: #notes{

If I remove the query string parameter 't' then no compilation errors occur.

Does anyone have a solution?

Thanks,

Paul.

Answer 1

The issue occurs due to a possible bug in dotless WebOptimization Adapter.

To workaround the issue, please add disableParameters="true" to dotless configuration section in your Web.config as shown below:

<dotless minifyCss="false" cache="true" web="true" disableParameters="true" />

Answer 2

I just solved the problem by updating dotless and dotless adapterfor System.Web.Optimization to their last available versions:

• dotless: new version 1.5.0
• dotless adapterfor System.Web.Optimization: new version 1.3.3

For history on this problem, and the resolution, see the GitHub issue "Empty CSS generation at startup" and the related pull request that fixed it.