tpl: Add os.fileExists template function

[digitalcraftsman]

This pull request is intended to fix #3839

Currently, I've an issue with the test cases. fileExists returns a boolean and an error / nil.

Due to the type assertion false can become ambiguous: it can either mean that a file does not exist or that an error is expected.

If the file does not exist, fileExists returns false (correctly), implicating that no error occurred, but the test fails because false is interpreted like an expected error.

Any ideas how this ambiguity can be circumvented?

[bep]

Any ideas how this ambiguity can be circumvented?

Check the error returned from Stat.

if !os.IsNotExist(err) {
   return err
}

return false

[bep]

@moorereason @digitalcraftsman status?

[bep]

In general, it would be great if you could check if your PR goes green before you leave it to dry.

[NicoHood]

This function seems to only work with absolute paths. Could some please help me (add this to the docs as well!) to use a relative path (checking if an image inside the posts folder exists), or update the function to support both?

I used this dirty workaround:

        {{ $imgPath := print "/content/" $.Dir "header.png" }}
        {{ if (fileExists $imgPath) -}}
              <img alt="{{ .Title }}" class="img-fluid mb-2" src="header.png" />
        {{ end }}

[moorereason]

@NicoHood, please don't comment on issues that were closed 3 years ago. Open a new ticket or ask on the discussion forums.