How to include custom attributes in asciidoc book

I have an asciidoc book that consists of several .adoc files, and I want to use a custom attribute in each file.

I've created .attribute.adoc and included it in each file like this:

include::.attriutes.adoc[]

It works... but at the end of each chapter (one .adoc file is one chapter) asciidoctor renders the "include statement" as-is. Let's assume .attribute.adc contains the following string:

:appname: MyApp

asciidoctor replaces each occurrence of {appname} with MyApp, but also adds the string :appname: MyApp to the end of the chapter. Any idea?

In the end, the only way to make this work correctly, was to pass the custom attribute (appname) to asciidoctor-pdf. Here's a snippet of my Makefile:

$(PDF_FILE): $(ADOC_FILES) | $(PDF_DIR)
    bundle exec asciidoctor-pdf \
        -r asciidoctor-diagram \
        -a appname=$(APPNAME) \
        -a imagesdir=$(IMGDIR) \
        -a pdf-themesdir=$(THEMEDIR) \
        -a pdf-fontsdir="$(THEMEDIR);GEM_FONTS_DIR" \
        -a pdf-theme=custom \
        $(SRCDIR)/main.adoc \
        -o $@

Passing appname to asciidoctor-pdf solves my problem... and the resulting PDF no longer contains :appname: MyApp at end of some chapters.