xlog/ppx/xlog_ppx.ml

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open Ppxlib
let log_expander ~ctxt (e : expression) (l : (arg_label * expression) list) : expression =
let loc = Expansion_context.Extension.extension_point_loc ctxt in
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let open (val Ast_builder.make loc) in
let (is_exn, err) = begin match e.pexp_desc with
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| Pexp_ident { txt = Lident "trace"; _ }
| Pexp_ident { txt = Lident "debug"; _ }
| Pexp_ident { txt = Lident "info"; _ }
| Pexp_ident { txt = Lident "warn"; _ }
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| Pexp_ident { txt = Lident "error"; _ } -> (false, None)
| Pexp_ident { txt = Lident "exn"; _ } -> (true, None)
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| _ ->
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(false,
Some (pexp_extension @@ Location.error_extensionf ~loc
"log type must be one of: trace, debug, info, warn, error, exn"))
end in match err with
| Some err -> err
| None ->
if is_exn then
match l with
| [] ->
pexp_extension @@ Location.error_extensionf ~loc
"must provide exn value"
| (_, v)::l ->
let application =
eapply (pexp_ident { txt = Lident "m"; loc}) (List.map snd l) in
[%expr [%e e] [%e v] (Printexc.get_raw_backtrace ()) ~__POS__ ~__FUNCTION__
(fun m -> [%e application])]
else
let application =
eapply (pexp_ident { txt = Lident "m"; loc}) (List.map snd l) in
[%expr [%e e] ~__POS__ ~__FUNCTION__ (fun m -> [%e application])]
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let log_extension =
let pattern =
let open Ast_pattern in
pstr (pstr_eval (pexp_apply __ __) nil ^:: nil)
in
Context_free.Rule.extension
(Extension.V3.declare "xlog" Expression pattern log_expander)
let import_expander ~ctxt _e : structure_item =
let loc = Expansion_context.Extension.extension_point_loc ctxt in
[%stri include (val Xlog.logs __FUNCTION__)]
let import_extension =
let pattern =
let open Ast_pattern in
__
in
Context_free.Rule.extension
(Extension.V3.declare "xlog_import" Structure_item pattern import_expander)
let () =
Driver.register_transformation
~rules:[ log_extension; import_extension ]
"xlog.ppx"