asdf install [warning] /usr/bin/fop Fop is missing. Using fakefop to generate placeholder PDF files

Question

When installing Erlang using asdf version manager, the above build warning indicates that the apache fop library has either not been installed on the system, or has not been recognised by the asdf version manager. The result is that the Erlang documentation will not be installed as a part of the installation.

Error encountered when executing the following command:

asdf install erlang <version>

Answer 1

This error is related to the fact that you MUST abide by the platform requirements listed in the asdf Erlang extension page.

Personally, I'm using MATE on Ubuntu 18.10 - Cosmic Cuttlefish. To satisfy the asdf runtime requirements for Ubuntu, I needed to install the following Check the Erlang extension page for your specific platform's requirements:

sudo apt-get install libwxbase3.0-0v5 \
    libwxbase3.0-dev \
    libwxgtk3.0-0v5 \
    libwxgtk3.0-dev \
    libwxgtk3.0-gtk3-0v5 \
    libwxgtk3.0-gtk3-dev \
    wx3.0-doc \
    wx3.0-examples \
    wx3.0-headers \
    wx3.0-i18n \
    wx-common \
    libwxgtk-webview3.0-gtk3-0v5 \
    libwxgtk-webview3.0-gtk3-dev \
    libwxgtk-media3.0-0v5 \
    libwxgtk-media3.0-dev \
    libwxgtk-media3.0-gtk3-0v5 \
    libwxgtk-media3.0-gtk3-dev

Once you have satisfied the platform requirements, you can safely go ahead and re-process the asdf Erlang installation successfully with the following syntax:

 asdf install erlang <version>

If after completing the installation the documentation has still not been installed, check this StackOverflow answer for assistance with this