Uniform paths (#1153)

This patch resolves #1132 by precomputing the various paths used by Links. The paths are computed during compilation of Links itself. The paths change depending on whether Links was compiled via `opam install` or `make`/`dune build`. In the former case, all the paths are computed relative to the OPAM root of the running switch, whereas in the latter case the paths are computed relative to the source tree that `make` was invoked in. Consequently, Links no longer has to guess or compute paths during startup (well this is a truth with modifications, database drivers are still discovered dynamically, and the default config file is still implicitly resolved if built from source as the testing infrastructure depends on being able to control the config file via the environment variable `LINKS_CONFIG`). In addition, this patch also deprecates the `LINKS_LIB` environment variable, i.e. setting this variable no longer affects the runtime of Links.

Co-authored-by: Daniel Hillerström <daniel.hillerstrom@ed.ac.uk>

Author: Yi-Zhou-01

Makefile

@@ -176,3 +176,8 @@ opam-release:
 	dune-release publish -p $(RELEASE_PKGS) distrib
 	dune-release opam -p $(RELEASE_PKGS) pkg
 	dune-release opam -p $(RELEASE_PKGS) submit
+
+# Build Links
+.PHONY: opam-build-links.opam
+opam-build-links.opam: links.opam
+	$(shell LINKS_BUILT_BY_OPAM=1 dune build -p links)

bin/driver.ml

@@ -5,12 +5,7 @@ open Utility
 
 (** Name of the file containing the prelude code. *)
 let prelude_file =
-  let prelude_dir =
-    match Utility.getenv "LINKS_LIB" with
-    (* If user defined LINKS_LIB then it takes the highest priority *)
-    | Some path -> path
-    | None -> locate_file "prelude.links" in
-  Settings.(option ~default:(Some (Filename.concat prelude_dir "prelude.links")) "prelude"
+  Settings.(option ~default: (Some Linkspath.prelude) "prelude"
             |> synopsis "The Links prelude source file"
             |> to_string from_string_option
             |> convert (Sys.expand ->- some)
@@ -237,20 +232,7 @@ module Phases = struct
             Js_CodeGen.output oc Compiler.primitive_bindings;
             let runtime_files =
               match Settings.get Basicsettings.System.custom_js_runtime with
-              | [] ->
-                let file =
-                  begin match Settings.get jslib_dir with
-                    | None | Some "" ->
-                      begin
-                        Filename.concat
-                          (match Utility.getenv "LINKS_LIB" with
-                            | None -> Filename.dirname Sys.executable_name
-                            | Some path -> path)
-                            (Filename.concat "js" "jslib.js")
-                      end
-                    | Some path -> Filename.concat path "jslib.js"
-                  end
-                in [file]
+              | [] -> [Filename.concat Linkspath.jslib "jslib.js"]
               | files -> files
             in
             List.iter

core/dune

@@ -20,6 +20,11 @@
              findlib menhirLib links.lens calendar)
   (preprocess (pps ppx_deriving.std ppx_deriving_yojson)))
 
+(rule
+  (targets linkspath.ml)
+  (deps (:gen ../gen_linkspath/gen_linkspath.exe))
+  (action (run %{gen} -o %{targets})))
+
 ;; Make Query modules available.
 (copy_files# query/*.ml)
 (copy_files# query/*.mli)

core/moduleUtils.ml

@@ -23,12 +23,7 @@ let use_stdlib
 
 (* Standard library path *)
 let stdlib_path =
-  let dir =
-    match Utility.getenv "LINKS_LIB" with
-    | Some path -> Filename.concat path "stdlib"
-    | None -> ""
-  in
-  Settings.(option ~default:(Some dir) "stdlib_path"
+  Settings.(option ~default:(Some Linkspath.stdlib) "stdlib_path"
             |> to_string from_string_option
             |> convert Utility.(Sys.expand ->- some)
             |> sync)

core/settings.ml

@@ -1130,23 +1130,14 @@ let config_loaded = ref false
 let config =
   (* Path to the default config file. *)
   let default_config_file =
-    match Utility.getenv "LINKS_CONFIG" with
-    (* If user defined LINKS_CONFIG then it takes the highest priority. *)
-    | Some path -> Some (Filename.concat path "config")
+    (* If there exists a precomputed path then use it as the default config. *)
+    match Linkspath.config with
     | None ->
-       (* If LINKS_CONFIG is not defined then we search in current directory. *)
-       let executable_dir = Filename.dirname Sys.executable_name in
-       if Sys.file_exists (Filename.concat executable_dir "config")
-       then Some (Filename.concat executable_dir "config")
-       else try
-           (* If all else failed we search for OPAM installation of Links and
-            use a config that it provides. *)
-           let opam_links_etc =
-             input_line (Unix.open_process_in "opam config var links:etc 2>/dev/null") in
-           if Sys.file_exists (Filename.concat opam_links_etc "config")
-           then Some (Filename.concat opam_links_etc "config")
-           else None
-         with End_of_file -> None
+       (* If LINKS_CONFIG is defined then use it as the default config. *)
+       (match Utility.getenv "LINKS_CONFIG" with
+       | Some path -> Some (Filename.concat path "config")
+       | None -> None)
+    | Some path -> Some path
   in
   (* Load default is the action attached to the [config] setting. If
      [config_loaded] is false it will try to load whatever argument it

core/webserver.ml

@@ -5,7 +5,7 @@ open Utility
 open Webserver_types
 open Var
 
-let jslib_dir = Settings.(option "jslibdir"
+let jslib_dir = Settings.(option ~default:(Some Linkspath.jslib) "jslibdir"
                           |> synopsis "Server-side (physical) location of the JavaScript runtime"
                           |> to_string from_string_option
                           |> convert Utility.(Sys.expand ->- some)

gen_linkspath/dune

@@ -0,0 +1,3 @@
+(executable
+ (name gen_linkspath)
+ (libraries dune.configurator))

gen_linkspath/gen_linkspath.ml

@@ -0,0 +1,28 @@
+module C = Configurator.V1
+
+let check_opam =
+  Sys.getenv_opt "LINKS_BUILT_BY_OPAM" |> Option.is_some
+
+let _ =
+  let oc = open_out "linkspath.ml" in 
+      if check_opam
+      then
+        (* If Links is built by OPAM*)
+        let lib_path = input_line (Unix.open_process_in "opam var lib") in
+        let etc_path = input_line (Unix.open_process_in "opam var etc") in
+        let share_path = input_line (Unix.open_process_in "opam var share") in
+          Printf.fprintf oc "let config = Some \"%s/links/config\"\n" etc_path;
+          Printf.fprintf oc "let jslib = \"%s/links/js\"\n" lib_path;
+          Printf.fprintf oc "let examples = \"%s/links/examples\"\n" share_path;
+          Printf.fprintf oc "let stdlib = \"%s/links/stdlib\"\n" lib_path;
+          Printf.fprintf oc "let prelude = \"%s/links/prelude.links\"\n" lib_path;
+          close_out oc
+      else 
+        (* If Links is complied from source*)
+        let git_path =  input_line (Unix.open_process_in "git rev-parse --show-toplevel") in
+          Printf.fprintf oc "let config = %s\n" "None";
+          Printf.fprintf oc "let jslib = \"%s/lib/js\"\n" git_path;
+          Printf.fprintf oc "let examples = \"%s/examples\"\n" git_path;
+          Printf.fprintf oc "let stdlib = \"%s/lib/stdlib\"\n" git_path;
+          Printf.fprintf oc "let prelude = \"%s/prelude.links\"\n" git_path;
+        close_out oc

links.opam

@@ -11,9 +11,8 @@ version: "0.9.7"
 
 
 build: [
-  [ "dune" "subst" ] {dev}
-  [ "dune" "exec" "preinstall/preinstall.exe" "--" "-libdir" _:lib ]
-  [ "dune" "build" "-p" name "-j" jobs ]
+  ["dune" "exec" "preinstall/preinstall.exe" "--" "-libdir" _:lib]
+  [make "opam-build-links.opam"]
 ]
 
 depends: [