0005548: ocamlbuild's ocamlfind integration doesn't support syntax extensions

Notes
(0007112) gasche (developer) 2012-03-20 11:09	I discussed this with xclerc and therefore mark this as "acknowledged". If someone in the respected audience has a patch, please submit it! (Sane) contributions to fix ocamlbuild deficiencies are always welcome.

(0008042) meyer (developer) 2012-09-10 05:16	So ocamlbuild just does not use ocamlfind in this case. This definetely needs fixing.

(0009518) gasche (developer) 2013-06-16 19:38	This PR has in fact seen invisible progress: in the SVN commit 13262, Wojciech implemented a "-syntax <foo>" command-line option for ocamlbuild, meant to be used exactly as for ocamlfind. It is equivalent to passing the tag "syntax(foo)". You can therefore use ocamlbuild -use-ocamlfind -syntax camlp4o -package foo.syntax test.byte to compile test.ml into test.byte. For example for test.ml as such: IFDEF BLAH THEN print_endline "foo" END You can use the two equivalent commands: ocamlbuild -use-ocamlfind -tag "syntax(camlp4o -DBLAH)" -package camlp4.macro test.byte ocamlbuild -use-ocamlfind -syntax "camlp4o -DBLAH" -package camlp4.macro test.byte However, the target .pp.ml still does not work as expected. I know of no easy way to call ocamlfind for only the preprocessing phase, and get source code as a result (in particular there is no "ocamlfind camlp4* -package ..." invocation possible. Options for implementing this would be to: (1) re-implement the build-camlp4-invocation-command logic in ocamlbuild (reusing the ocamlfind-like logic that was present before -use-ocamlfind was implemented), by calling "ocamlfind query" to get the right option to pass to the preprocessor; painful and probably not the best solution (2) work-around the issue the issue by internally calling "ocamlfind ocamlc -syntax camlp4o ... -dsource" to convince ocamlfind that he's invoking a compiler, but actually get the postprocessed source code from ocaml. Not satisfying right now as there is no "-stop-after-parsing" flag to feed to the compiler, and it would still e.g. fail on ill-typed files. It's still a credible option, and in particular could be the best one if we want pp.ml to also perform -ppx rewritings. (3) implement the "ocamlfind camlp4*" command. I have not contacted Gerd to know whether that would be possible, but I would suspect that if this (rather natural) feature is not present, he possibly has already considered that and has good reason not to do it. In any case, none of those options are realistic during a feature freeze, so I'm moving the .pp.ml part of this bug (the rest I consider solved) to 4.02+dev.

Issue History
Date Modified	Username	Field	Change
2012-03-20 11:07	gasche	New Issue
2012-03-20 11:09	gasche	Note Added: 0007112
2012-03-20 11:09	gasche	Status	new => acknowledged
2012-07-10 11:27	doligez	Target Version	=> 4.01.0+dev
2012-07-31 13:36	doligez	Target Version	4.01.0+dev => 4.00.1+dev
2012-09-10 05:16	meyer	Note Added: 0008042
2012-09-10 05:16	meyer	Assigned To	=> meyer
2012-09-10 05:16	meyer	Status	acknowledged => assigned
2012-09-21 13:50	doligez	Target Version	4.00.1+dev => 4.01.0+dev
2013-06-16 19:38	gasche	Note Added: 0009518
2013-06-16 19:38	gasche	Assigned To	meyer => gasche
2013-06-16 19:38	gasche	Target Version	4.01.0+dev => 4.02.0+dev
2013-06-16 21:26	gasche	Severity	minor => feature

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