Reason V4 [Stacked Diff 1/n #2605] [Allow multiple versions of Reason]

Summary:This allows multiple versions of Reason in a single project by
inferring and recording the version of syntax used into the file in an
attribute. The attribute allows us to switch the parser and lexer on the
fly. This attribute is not the only way we can infer the version, and we
can allow project level configuration, but this is the approach that is
guaranteed to work with any build system or tooling.

Test Plan:

Reviewers:

CC:

docs/RELEASING.md

@@ -16,14 +16,32 @@ and `rtop.json` respectively in the repo root, you would run that script after
 committing/bumping some versions:
 
 
+**IMPORTANT: Update The Version Numbers In Packages:**
+1. Make sure the version number in `esy.json` and `reason.json` is the new
+   version number for the release.
+2. Make sure the file
+   [../../src/reason-version/reason_version.ml](../../src/reason-version/reason_version.ml)
+   also has that same version number that `refmt` has:
+
 ```sh
 git checkout -b MYRELEASE origin/master
 git rebase origin/master
-vim -O esy.json reason.json
-# Then edit the version number accordingly on BOTH files. With that same VERSION do:
-version=3.5.0 make pre_release
+vim -O esy.json reason.json src/reason-version/reason_version.ml
+
+# Edit version field in jsons, and make sure reason_version has the new version
+# let package_version = {
+#   major = 3;
+#   minor = 7;
+#   patch = 0;
+# }
+
 git commit -m "Bump version"
 git push origin HEAD:PullRequestForVersion # Commit these version bumps
+
+```
+
+**Perform The Release:**
+```sh
 node ./scripts/esy-prepublish.js ./reason.json ./rtop.json
 
 # Then publish. For example:

src/reason-parser/dune

@@ -125,4 +125,5 @@
   reason.ocaml-migrate-parsetree
   menhirLib
   reason.easy_format
-  ppxlib))
+  ppxlib
+  reason.version))

src/reason-parser/reason_attributes.ml

@@ -12,6 +12,15 @@ type attributesPartition = {
   uncurried : bool
 }
 
+let is_stylistic_attr = function
+  | { attr_name = {txt="reason.raw_literal"}; _}
+  (* Consider warnings to be "stylistic" attributes - attributes that do not
+   * affect printing *)
+  | { attr_name = {txt="ocaml.ppwarn"}; _}
+  | { attr_name = {txt="reason.preserve_braces"}; _} -> true
+  | _ -> false
+
+
 (** Partition attributes into kinds *)
 let rec partitionAttributes ?(partDoc=false) ?(allowUncurry=true) attrs : attributesPartition =
   match attrs with
@@ -35,10 +44,7 @@ let rec partitionAttributes ?(partDoc=false) ?(allowUncurry=true) attrs : attrib
   | ({ attr_name = {txt="ocaml.doc" | "ocaml.text"}; _} as doc)::atTl when partDoc = true ->
     let partition = partitionAttributes ~partDoc ~allowUncurry atTl in
     {partition with docAttrs=doc::partition.docAttrs}
-  | ({ attr_name = {txt="reason.raw_literal"}; _} as attr) :: atTl ->
-    let partition = partitionAttributes ~partDoc ~allowUncurry atTl in
-    {partition with stylisticAttrs=attr::partition.stylisticAttrs}
-  | ({ attr_name = {txt="reason.preserve_braces"}; _} as attr) :: atTl ->
+  | attr :: atTl when is_stylistic_attr attr ->
     let partition = partitionAttributes ~partDoc ~allowUncurry atTl in
     {partition with stylisticAttrs=attr::partition.stylisticAttrs}
   | atHd :: atTl ->
@@ -62,8 +68,7 @@ let extract_raw_literal attrs =
 
 let without_stylistic_attrs attrs =
   let rec loop acc = function
-    | attr :: rest when (partitionAttributes [attr]).stylisticAttrs != [] ->
-        loop acc rest
+    | attr :: rest when is_stylistic_attr attr -> loop acc rest
     | [] -> List.rev acc
     | attr :: rest -> loop (attr :: acc) rest
   in

src/reason-parser/reason_declarative_lexer.mll

@@ -451,6 +451,7 @@ rule token state = parse
     { SHARPEQUAL }
   | "#" operator_chars+
     { SHARPOP (lexeme_operator lexbuf) }
+  (* File name / line number source mapping # n string\n *)
   | "#" [' ' '\t']* (['0'-'9']+ as num) [' ' '\t']*
         ("\"" ([^ '\010' '\013' '"' ] * as name) "\"")?
         [^ '\010' '\013'] * newline
@@ -552,24 +553,38 @@ rule token state = parse
     }
   | "[|<"
     { set_lexeme_length lexbuf 2;
+      (* TODO: See if decompose_token in Reason_single_parser.ml would work better for this *)
       LBRACKETBAR
     }
     (* allow parsing of <div /></Component> *)
   | "/></" uppercase_or_lowercase+
     { (* allow parsing of <div asd=1></div> *)
+      (* TODO: See if decompose_token in Reason_single_parser.ml would work better for this *)
       set_lexeme_length lexbuf 2;
       SLASHGREATER
     }
   | "></" uppercase_or_lowercase+
     { (* allow parsing of <div asd=1></div> *)
+      (* TODO: See if decompose_token in Reason_single_parser.ml would work better for this *)
       set_lexeme_length lexbuf 1;
       GREATER
     }
   | "><" uppercase_or_lowercase+
     { (* allow parsing of <div><span> *)
+      (* TODO: See if decompose_token in Reason_single_parser.ml would work better for this *)
       set_lexeme_length lexbuf 1;
       GREATER
     }
+  | "[@reason.version " (['0'-'9']+ as major) '.' (['0'-'9']+ as minor) (('.' ['0'-'9']+)? as _patch) ']' {
+    (* Special case parsing of attribute so that we can special case its
+     * parsing. Parses x.y.z even though it is not valid syntax otherwise -
+     * just gracefully remove the last number. The parser will ignore this
+     * attribute when parsed, and instead record its presence, and then inject
+     * the attribute into the footer of the file.  Then the printer will ensure
+     * it is formatted at the top of the file, ideally after the first file
+     * floating doc comment. *)
+    VERSION_ATTRIBUTE (int_of_string major, int_of_string minor)
+  }
   | "[@" { LBRACKETAT }
   | "[%" { LBRACKETPERCENT }
   | "[%%" { LBRACKETPERCENTPERCENT }