[buck/java2] rely on (and modify) PATH to find infer binary to improve caching

Summary:
The genrule-capture integration with Java relies on a buck config flag `infer.infer_bin=<path to infer>` (see test changes in `DEFS` below).
In a CI environment where the infer binary is checked out under a random directory, this means that the buck genrule is keyed by a random string (the path to infer), and this defeats caching.

Switch to the following contract: the genrule target does not expect a config flag at all.  Instead it runs whichever `infer` binary is in the path.  To make sure the binary is the same one with the originator, the capture integration runs buck under a modified `PATH` where the originator `infer` is sure to be the first matching entry.

NB cache invalidation is still OK because we rely on `infer.version` buck config flag, which will be hashed into the rulekey.

Reviewed By: jvillard

Differential Revision: D16332696

fbshipit-source-id: 2975d5c26

infer/src/base/Config.mli

@@ -89,8 +89,6 @@ val etc_dir : string
 
 val events_dir_name : string
 
-val exe_basename : string
-
 val fail_on_issue_exit_code : int
 
 val frontend_stats_dir_name : string

infer/src/base/Utils.mli

@@ -67,6 +67,8 @@ val consume_in : In_channel.t -> unit
 val echo_in : In_channel.t -> unit
 (** echo the lines we get to stdout until End_of_file is reached *)
 
+val with_channel_in : f:(string -> unit) -> In_channel.t -> unit
+
 val with_process_in : string -> (In_channel.t -> 'a) -> 'a * Unix.Exit_or_signal.t
 
 val with_process_lines :

infer/src/integration/Buck.ml

@@ -160,9 +160,7 @@ let die_if_empty f = function [] -> f L.(die UserError) | l -> l
 let buck_config =
   lazy
     ( if Config.genrule_master_mode then
-      [ "infer.version=" ^ Version.versionString
-      ; "infer.infer_bin=" ^ Config.bin_dir ^/ Config.exe_basename
-      ; "infer.mode=capture" ]
+      ["infer.version=" ^ Version.versionString; "infer.mode=capture"]
       |> List.fold ~init:[] ~f:(fun acc f -> "--config" :: f :: acc)
     else [] )
 

infer/src/integration/BuckGenrule.ml

@@ -24,9 +24,26 @@ let write_infer_deps infile =
 
 let run_buck_capture cmd =
   let buck_output_file = Filename.temp_file "buck_output" ".log" in
-  let shell_cmd = List.map ~f:Escape.escape_shell cmd |> String.concat ~sep:" " in
-  let shell_cmd_redirected = Printf.sprintf "%s >'%s'" shell_cmd buck_output_file in
-  match Utils.with_process_in shell_cmd_redirected Utils.consume_in |> snd with
+  let shell_cmd =
+    List.map ~f:Escape.escape_shell cmd
+    |> String.concat ~sep:" "
+    |> fun cmd -> Printf.sprintf "%s >'%s'" cmd buck_output_file
+  in
+  let path_var = "PATH" in
+  let new_path =
+    Sys.getenv path_var
+    |> Option.value_map ~default:Config.bin_dir ~f:(fun old_path -> Config.bin_dir ^ ":" ^ old_path)
+  in
+  let env = `Extend [(path_var, new_path)] in
+  let ({stdin; stdout; stderr; pid} : Unix.Process_info.t) =
+    Unix.create_process_env ~prog:"sh" ~args:["-c"; shell_cmd] ~env ()
+  in
+  let buck_stderr = Unix.in_channel_of_descr stderr in
+  Utils.with_channel_in buck_stderr ~f:(L.progress "BUCK: %s@.") ;
+  Unix.close stdin ;
+  Unix.close stdout ;
+  In_channel.close buck_stderr ;
+  match Unix.waitpid pid with
   | Ok () ->
       write_infer_deps buck_output_file ; Unix.unlink buck_output_file
   | Error _ as err ->

infer/tests/build_systems/genrulecapture/DEFS

@@ -3,9 +3,6 @@ import os
 original_java_library = java_library
 original_android_library = android_library
 
-def _get_infer_bin():
-  return read_config("infer", "infer_bin")
-
 def _get_project_root():
   return "\$(git rev-parse --show-toplevel)/infer/tests/build_systems/genrulecapture"
 
@@ -38,7 +35,7 @@ def _infer_capture_genrule(
     "echo {} >> {}".format(arg, args_file)
     for arg in args
   ] + [
-    " ".join([_get_infer_bin(), "@" + args_file])
+    "infer @" + args_file
   ]
 	
   genrule(