specifications: Preprocess the spec for properly rendering mermaid di…

…agrams

In order for mermaid diagrams to render properly on both github and the
generated PDF, we need to preprocess the spec source and replace
[source,mermaid] occurences with [mermaid] ones.

Signed-off-by: Samuel Ortiz <sameo@rivosinc.com>

specification/Makefile

@@ -10,6 +10,7 @@ build:
 		--attribute=pdf-fontsdir=docs-resources/fonts \
 		--attribute=pdf-style=docs-resources/themes/riscv-pdf.yml \
 		--failure-level=ERROR \
+		--require=./preprocessor.rb \
 		--require=asciidoctor-bibtex \
 		--require=asciidoctor-diagram \
 		--require=asciidoctor-mathematical \

specification/preprocessor.rb

@@ -0,0 +1,20 @@
+require 'asciidoctor'
+require 'asciidoctor/extensions'
+
+require 'asciidoctor/extensions'
+
+Asciidoctor::Extensions.register do
+  preprocessor do
+    process do |document, reader|
+      new_lines = []
+      reader.readlines.each do |line|
+        if line.strip == "[source,mermaid]"
+          new_lines << "[mermaid]"
+        else
+          new_lines << line
+        end
+      end
+      Asciidoctor::Reader.new(new_lines)
+    end
+  end
+end