improve OCaml version file error

Author: Nymphium

.gitignore

@@ -139,4 +139,6 @@ jscomp/outcome_printer/reason_syntax_util.ml
 jscomp/outcome_printer/reason_syntax_util.mli
 jscomp/bin/all_ounit_tests.ml
 native/
-vendor/ocaml
+vendor/ocaml
+OCAML_VERSION
+ocaml/VERSION

scripts/buildocaml.js

@@ -29,6 +29,10 @@ function getVersionPrefix() {
     cached = version.substr(0, version.indexOf("+"));
     return cached;
   }
+
+  console.error(`cannot find '${file}'`);
+  console.error("You should create OCAML_VERSION or ocaml/VERSION file to specify OCaml version like '4.02.3+buckle-master'");
+  console.error("For example, run `opam switch show > OCAML_VERSION`");
   throw new Error("version file not found");
 }
 exports.getVersionPrefix = getVersionPrefix;

scripts/install.js

@@ -357,7 +357,7 @@ function provideCompiler() {
     var releaseNinja = require("./ninjaFactory.js").libNinja({
       ocamlopt: "ocamlopt.opt",
       ext: ".exe",
-      INCL: require("./buildocaml.js").getVersionPrefix()
+      INCL: ocamlVersion
     });
 
     var filePath = path.join(lib_dir, "release.ninja");

scripts/prebuilt.js

@@ -8,7 +8,7 @@ var root_config = { cwd: root, stdio: [0, 1, 2] }
 process.env.BS_RELEASE_BUILD = 'true'
 
 
-var version = require('./buildocaml.js').getVersionPrefix()
+var ocamlVersion = require('./buildocaml.js').getVersionPrefix()
 var fs = require('fs')
 var hostPlatform = 'darwin'
 
@@ -19,9 +19,9 @@ function buildCompiler() {
   // delete process.env.OCAMLLIB
   var prebuilt = 'prebuilt.ninja'
   var content = require('./ninjaFactory.js').libNinja({
-    ocamlopt : is_windows?`ocamlopt.opt.exe`:`../native/${version}/bin/ocamlopt.opt`,
+    ocamlopt : is_windows?`ocamlopt.opt.exe`:`../native/${ocamlVersion}/bin/ocamlopt.opt`,
     ext : sys_extension,
-    INCL : version
+    INCL : ocamlVersion
   })
 
   fs.writeFileSync(path.join(root,'lib',prebuilt),content,'ascii')