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Why does the Yesod install fail with "cannot find normal object file `dist/build/yesod/yesod-tmp/CodeGen.o'"?

The Yesod package includes an executable that uses some Template Haskell. Due to the way GHC works, there are a few hoops to jump through to get this to compile when profiling is enabled. To get around the issue, try installing Yesod with:

cabal install yesod --disable-executable-profiling

Why does Yesod have a special syntax for coding CSS and Javascript?

This practice is already common in the web development world, with Sass and Coffeescript. Here's a number of reasons why we do this in Yesod:

  • Julius (Javascript) actually isn't a different syntax at all, it's simply a pass-through parser.
  • With Lucius and Cassius (for CSS), each one provides some syntactic sugar over plain CSS that people like.
  • All three languages allow for variable interpolation, including type-safe URL interpolation.
  • Lucius and Cassius automatically minify their output.
  • We get many compile-time checks, but on variable existence and correct typeness, and well-formedness of the file.
  • These systems compose very nicely via widgets.
  • And via these widgets, we're able to easily concatenate multiple templates into a single file to be efficiently served via one HTTP request.

With "yesod devel" I get an error like "unknown symbol __stginit_foozm0zi0zi0_HandlerziFoo_"

Make sure that all your Handler files are listed in the cabal file, in the other-modules section.

Why is UTCTime stored as TIMESTAMP WITHOUT TIME ZONE? Shouldn't it be WITH TIME ZONE?

Please see PostgreSQL-UTCTime for more information.

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