[build] disable legacy_parser by default, see make config

.github/workflows/main.yml

@@ -93,6 +93,7 @@ jobs:
         run: |
           opam depext camlp5 || true # no depext on opam 2.1
           opam install 'camlp5>=8'
+          opam exec -- make config LEGACY_PARSER=1
   
       - name: Install real dependencies
         run: |

Makefile

@@ -40,6 +40,12 @@ CP5:=$(shell if ocamlfind query camlp5 2>/dev/null >&2; then : ; else echo "INFO
 build:
 	dune build $(DUNE_OPTS) @all
 
+config:
+	@(if [ -z $$LEGACY_PARSER ]; \
+	then echo '(dirs :standard \ legacy_parser)'; \
+	else echo '(dirs :standard )'; \
+	fi ) > src/dune.config
+
 install:
 	dune install $(DUNE_OPTS)
 

README.md

@@ -29,6 +29,8 @@ you can type
 opam pin add elpi https://github.com/LPCIC/elpi.git
 ```
 You can also clone this repository and type `make build`.
+If you want to build the legacy parser, do begin with
+`make config LEGACY_PARSER=1` and then `make build`.
 
 Finally, each CI run builds statically linked binaries for the
 three supported operating systems, click on any

src/dune

@@ -61,3 +61,5 @@
       (echo "% File generated by elpi -document-builtins, do not edit")
       (run elpi -document-builtins))))
 )
+
+(include dune.config)

src/dune.config

@@ -0,0 +1 @@
+(dirs :standard \ legacy_parser)

src/legacy_parser/dune

@@ -1,7 +1,6 @@
 (library
   (name elpi_legacy_parser)
   (public_name elpi.legacy_parser)
-  (optional)
   (libraries elpi.util elpi.parser camlp5.gramlib)
   (flags -w -A)
   (preprocess (per_module ((action (run camlp5o -I . -I +camlp5 pa_extend.cmo pa_lexer.cmo %{input-file})) parser)))