[comp-db] simple refactor

Summary:
- Remove some unnecessary mutation in compilation database management.
- Move capture code to CaptureCompilationDatabase module.
- Freeze `Config.clang_compilation_dbs` and remove mutations outside `Config`.

Reviewed By: martintrojer

Differential Revision: D24445244

fbshipit-source-id: f97dda522

infer/src/base/Config.ml

@@ -2721,6 +2721,8 @@ and checkers = List.map !all_checkers ~f:(fun (checker, _, var) -> (checker, !va
 
 and clang_biniou_file = !clang_biniou_file
 
+and clang_compilation_dbs = !clang_compilation_dbs
+
 and clang_compound_literal_init_limit = !clang_compound_literal_init_limit
 
 and clang_extra_flags = !clang_extra_flags

infer/src/base/Config.mli

@@ -648,4 +648,4 @@ val scuba_execution_id : Int64.t option
 
 (** {2 Global variables with initial values specified by command-line options} *)
 
-val clang_compilation_dbs : [`Escaped of string | `Raw of string] list ref
+val clang_compilation_dbs : [`Escaped of string | `Raw of string] list

infer/src/integration/CaptureCompilationDatabase.ml

@@ -157,3 +157,16 @@ let capture_files_in_database ~changed_files compilation_database =
         fun source_file -> SourceFile.Set.mem source_file changed_files_set
   in
   run_compilation_database compilation_database filter_changed
+
+
+let capture ~changed_files ~db_files =
+  let root = Config.project_root in
+  let clang_compilation_dbs =
+    List.map db_files ~f:(function
+      | `Escaped fname ->
+          `Escaped (Utils.filename_to_absolute ~root fname)
+      | `Raw fname ->
+          `Raw (Utils.filename_to_absolute ~root fname) )
+  in
+  let compilation_database = CompilationDatabase.from_json_files clang_compilation_dbs in
+  capture_files_in_database ~changed_files compilation_database

infer/src/integration/CaptureCompilationDatabase.mli

@@ -7,11 +7,6 @@
 
 open! IStd
 
-val capture_files_in_database :
-  changed_files:SourceFile.Set.t option -> CompilationDatabase.t -> unit
-(** Run the capture of the files for which we have compilation commands in the database and in
-    [changed_files], if specified. *)
-
 val get_compilation_database_files_buck :
   BuckMode.clang_compilation_db_deps -> prog:string -> args:string list -> [> `Raw of string] list
 (** Get the compilation database files that contain the compilation given by the buck command. It
@@ -22,3 +17,10 @@ val get_compilation_database_files_xcodebuild :
   prog:string -> args:string list -> [> `Escaped of string] list
 (** Get the compilation database files that contain the compilation given by the xcodebuild command,
     using xcpretty. *)
+
+val capture :
+     changed_files:SourceFile.Set.t option
+  -> db_files:[< `Escaped of string | `Raw of string] list
+  -> unit
+(** Run the capture of the files for which we have compilation commands in [db_files] and
+    [changed_files], if specified. *)

infer/src/integration/CompilationDatabase.ml

@@ -10,14 +10,12 @@ module L = Logging
 
 type compilation_data = {directory: string; executable: string; escaped_arguments: string list}
 
-type t = compilation_data SourceFile.Map.t ref
+type t = compilation_data SourceFile.Map.t
 
-let empty () = ref SourceFile.Map.empty
-
-let get_size database = SourceFile.Map.cardinal !database
+let empty = SourceFile.Map.empty
 
 let filter_compilation_data database ~f =
-  SourceFile.Map.filter (fun s _ -> f s) !database |> SourceFile.Map.bindings
+  SourceFile.Map.filter (fun s _ -> f s) database |> SourceFile.Map.bindings
 
 
 let parse_command_and_arguments command_and_arguments =
@@ -49,7 +47,7 @@ let decode_json_file (database : t) json_format =
   let exit_format_error error =
     L.(die ExternalError) ("Json file doesn't have the expected format: " ^^ error)
   in
-  let parse_command json =
+  let parse_command db json =
     let directory = ref None in
     let file = ref None in
     let command = ref None in
@@ -126,21 +124,20 @@ let decode_json_file (database : t) json_format =
         let compilation_data = {directory; executable; escaped_arguments} in
         let abs_file = if Filename.is_relative file then directory ^/ file else file in
         let source_file = SourceFile.from_abs_path abs_file in
-        database := SourceFile.Map.add source_file compilation_data !database
+        SourceFile.Map.add source_file compilation_data db
     | _ ->
         exit_format_error "Compilation database entry is not an object: %s"
           (Yojson.Basic.to_string json)
   in
   match Yojson.Basic.from_file json_path with
   | `List commands ->
-      List.iter ~f:parse_command commands
+      List.fold ~init:database ~f:parse_command commands
   | _ as json ->
       exit_format_error "Compilation database is not a list of commands: %s"
         (Yojson.Basic.to_string json)
 
 
 let from_json_files db_json_files =
-  let db = empty () in
-  List.iter ~f:(decode_json_file db) db_json_files ;
-  L.(debug Capture Quiet) "created database with %d entries@\n" (get_size db) ;
+  let db = List.fold ~init:empty ~f:decode_json_file db_json_files in
+  L.(debug Capture Quiet) "created database with %d entries@\n" (SourceFile.Map.cardinal db) ;
   db

infer/src/integration/Driver.ml

@@ -104,18 +104,6 @@ let check_xcpretty () =
          @."
 
 
-let capture_with_compilation_database db_files =
-  let root = Config.project_root in
-  Config.clang_compilation_dbs :=
-    List.map db_files ~f:(function
-      | `Escaped fname ->
-          `Escaped (Utils.filename_to_absolute ~root fname)
-      | `Raw fname ->
-          `Raw (Utils.filename_to_absolute ~root fname) ) ;
-  let compilation_database = CompilationDatabase.from_json_files !Config.clang_compilation_dbs in
-  CaptureCompilationDatabase.capture_files_in_database compilation_database
-
-
 let capture ~changed_files = function
   | Analyze ->
       ()
@@ -130,10 +118,10 @@ let capture ~changed_files = function
       BuckGenrule.capture CombinedGenrule build_cmd
   | BuckCompilationDB {deps; prog; args} ->
       L.progress "Capturing using Buck's compilation database...@." ;
-      let json_cdb =
+      let db_files =
         CaptureCompilationDatabase.get_compilation_database_files_buck deps ~prog ~args
       in
-      capture_with_compilation_database ~changed_files json_cdb
+      CaptureCompilationDatabase.capture ~changed_files ~db_files
   | BuckGenrule {prog} ->
       L.progress "Capturing for Buck genrule compatibility...@." ;
       JMain.from_arguments prog
@@ -148,7 +136,7 @@ let capture ~changed_files = function
       Clang.capture compiler ~prog ~args
   | ClangCompilationDB {db_files} ->
       L.progress "Capturing using compilation database...@." ;
-      capture_with_compilation_database ~changed_files db_files
+      CaptureCompilationDatabase.capture ~changed_files ~db_files
   | Gradle {prog; args} ->
       L.progress "Capturing in gradle mode...@." ;
       Gradle.capture ~prog ~args
@@ -167,10 +155,10 @@ let capture ~changed_files = function
   | XcodeXcpretty {prog; args} ->
       L.progress "Capturing using xcodebuild and xcpretty...@." ;
       check_xcpretty () ;
-      let json_cdb =
+      let db_files =
         CaptureCompilationDatabase.get_compilation_database_files_xcodebuild ~prog ~args
       in
-      capture_with_compilation_database ~changed_files json_cdb
+      CaptureCompilationDatabase.capture ~changed_files ~db_files
 
 
 (* shadowed for tracing *)
@@ -363,9 +351,9 @@ let assert_supported_build_system build_system =
 let mode_of_build_command build_cmd (buck_mode : BuckMode.t option) =
   match build_cmd with
   | [] ->
-      if not (List.is_empty !Config.clang_compilation_dbs) then (
+      if not (List.is_empty Config.clang_compilation_dbs) then (
         assert_supported_mode `Clang "clang compilation database" ;
-        ClangCompilationDB {db_files= !Config.clang_compilation_dbs} )
+        ClangCompilationDB {db_files= Config.clang_compilation_dbs} )
       else Analyze
   | prog :: args -> (
       let build_system =