Improve opam metadata in dune

We add metadata that can be used to used to partially specify opam files. Common
fields such as depends, conflicts, authors, are all handled. Dune will now
automatically suggest corrections to the existing opam files based on this
metadata in the dune files

Signed-off-by: Anil Madhavapeddy <anil@recoil.org>
Signed-off-by: Rudi Grinberg <rudi.grinberg@gmail.com>

CHANGES.md

@@ -25,6 +25,10 @@ unreleased
   to produce targets that are present in the source tree. This has
   been a warning for long enough (#2068, @diml)
 
+- Add more opam metadata and use it to generate corrections to the .opam files
+  in the source. This allows the user to partially specify opam metadata in the
+  the dune-project file. (#2017, @avsm, @jonludlam)
+
 1.9.1 (11/04/2019)
 ------------------
 

doc/index.rst

@@ -22,6 +22,7 @@ Welcome to dune's documentation!
    configurator
    menhir
    jsoo
+   opam
    variants
    formatting
    coq

doc/opam.rst

@@ -0,0 +1,103 @@
+****
+opam
+****
+
+opam_ is the official package manager for OCaml, and dune offers some
+integration with it.
+
+Generating opam files
+=====================
+
+Dune is able to use metadata specified in the ``dune-project`` file to cross
+reference it with the information in the user written ``.opam`` file. To enable
+this integration, a user needs to add an ``(opam ..)`` field to the dune-project
+file.
+
+The fields that dune uses for this purpose are:
+
+- ``(license <name>)`` - Specified the license of the project
+
+- ``(authors <authors>)`` - A list of authors
+
+- ``(source <source>)`` - where the source is specified two ways:
+  ``(github <user/repo>)`` or ``(uri <uri>)``
+
+To enable dune suggesting corrections to the opam stanza, the user must specify
+an ``(opam <fields>)`` with the fields:
+
+- ``(tags <tags>)`` - Specify the list of tags for all packages
+- ``(depends <dep-specification>)`` - The list of dependencies shared by all opam packages
+  in this dune project
+- ``(conflicts <dep-specification>)`` - The list of conflicts shared by all opam
+  packages in this dune project
+- ``(package <package>)`` - the list of packages in this project and their
+  individual metadata.
+
+The list of dependencies ``<dep-specification>`` is modeled after opam's own
+language: The syntax is as a list of the following elements:
+
+.. code::
+   op := '=' | '<' | '>' | '<>' | '>=' | '<='
+
+   stage := :with_test | :build | :dev
+
+   constr := (<op> <version>)
+
+   logop := or | and
+
+   dep := (name <stage>)
+        | (name <constr>)
+        | (name (<logop> (<stage> | <constr>)*))
+
+   dep-specification = dep+
+
+The `(package <package>)` field contains the fields:
+
+- ``(name <string>)`` is the name of the package
+
+- ``(synopsis <string>)`` is a short package description
+
+- ``(description <string>)`` is a longer package description
+
+- ``(depends <dep-specification>)`` are package specific dependencies
+
+- ``(conflicts <dep-specification)`` are package specific conflicts
+
+Here's a complete example of a dune file with opam metadata specification:
+
+.. code:: scheme
+
+   (lang dune 1.10)
+   (name cohttp)
+   (source (github mirage/ocaml-cohttp))
+   (license ISC)
+   (authors "Anil Madhavapeddy" "Rudi Grinberg")
+
+   (opam
+     (tags org:mirage org:dune)
+     (depends
+     (ocaml (>= 4.06.0))
+     (cohttp (>= 1.0.0)))
+     (package
+       (name cohttp)
+       (synopsis "An OCaml library for HTTP clients and servers")
+       (description "A longer description")
+       (depends
+         (alcotest :with-test)
+         (dune (and :build (> 1.5)))
+         (foo (and :dev (> 1.5) (< 2.0)))
+         (uri (>= 1.9.0))
+         (uri (< 2.0.0))
+         (fieldslib (> v0.12))
+         (fieldslib (< v0.13))))
+     (package
+       (name cohttp-async)
+       (synopsis "HTTP client and server for the Async library")
+       (description "A _really_ long description")
+       (depends
+         (cohttp (>= 1.0.2))
+         (conduit-async (>= 1.0.3))
+         (async (>= v0.10.0))
+         (async (< v0.12)))))
+
+.. _opam: https://opam.ocaml.org/

dune-project

@@ -1,4 +1,38 @@
-(lang dune 1.8)
+(lang dune 1.10)
 (name dune)
 
-(implicit_transitive_deps false)
+(implicit_transitive_deps false)
+
+(license MIT)
+(authors "Jane Street Group, LLC <opensource@janestreet.com>")
+(source (github ocaml/dune))
+
+(opam
+ (package
+  (name dune)
+  (depends
+   (ocaml (>= 4.02))
+   base-unix
+   base-threads)
+  (conflicts
+   (jbuilder (<> "transition"))
+   (odoc (< 1.3.0)))
+  (synopsis "Fast, portable and opinionated build system")
+  (description "
+dune is a build system that was designed to simplify the release of
+Jane Street packages. It reads metadata from \"dune\" files following a
+very simple s-expression syntax.
+
+dune is fast, it has very low-overhead and support parallel builds on
+all platforms. It has no system dependencies, all you need to build
+dune and packages using dune is OCaml. You don't need or make or bash
+as long as the packages themselves don't use bash explicitly.
+
+dune supports multi-package development by simply dropping multiple
+repositories into the same directory.
+
+It also supports multi-context builds, such as building against
+several opam roots/switches simultaneously. This helps maintaining
+packages across several versions of OCaml and gives cross-compilation
+for free.
+")))

dune.opam

@@ -21,7 +21,6 @@ conflicts: [
   "jbuilder" {!= "transition"}
   "odoc" {< "1.3.0"}
 ]
-
 synopsis: "Fast, portable and opinionated build system"
 description: """
 dune is a build system that was designed to simplify the release of

example/sample-projects/hello_world/hello_world.opam

@@ -8,4 +8,4 @@ dev-repo: "git+https://github.com/SpongeBob/hello_world.git"
 license: "Apache-2.0"
 build: [
   ["dune" "build" "-p" name "-j" jobs]
-]
+]

example/sample-projects/with-configure-step/myproject.opam

@@ -8,4 +8,4 @@ dev-repo: "git+https://github.com/SpongeBob/myproject.git"
 license: "Apache-2.0"
 build: [
   ["dune" "build" "-p" name "-j" jobs]
-]
+]

src/blang.ml

@@ -15,6 +15,16 @@ module Op = struct
     | (Neq | Lt  | Lte) , Lt
     | (Neq | Gt  | Gte) , Gt -> true
     | _, _ -> false
+
+  let to_dyn =
+    let open Dyn.Encoder in
+    function
+    | Eq -> string "Eq"
+    | Gt -> string "Gt"
+    | Gte -> string "Gte"
+    | Lte -> string "Lte"
+    | Lt -> string "Lt"
+    | Neq -> string "Neq"
 end
 
 type t =
@@ -43,3 +53,52 @@ let rec eval t ~dir ~f =
     let x = String_with_vars.expand x ~mode:Many ~dir ~f
     and y = String_with_vars.expand y ~mode:Many ~dir ~f in
     Op.eval op (Value.L.compare_vals ~dir x y)
+
+let rec to_dyn =
+  let open Dyn.Encoder in
+  function
+  | Const b -> constr "Const" [bool b]
+  | Expr e -> constr "Expr" [via_sexp String_with_vars.to_sexp e]
+  | And t -> constr "And" (List.map ~f:to_dyn t)
+  | Or t -> constr "Or" (List.map ~f:to_dyn t)
+  | Compare (o, s1, s2) ->
+    constr "Compare"
+      [ Op.to_dyn o
+      ; via_sexp String_with_vars.to_sexp s1
+      ; via_sexp String_with_vars.to_sexp s2
+      ]
+
+let ops =
+  [ "=", Op.Eq
+  ; ">=", Gte
+  ; "<=", Lt
+  ; ">", Gt
+  ; "<", Lt
+  ; "<>", Neq
+  ]
+
+let decode =
+  let open Stanza.Decoder in
+  let ops =
+    List.map ops ~f:(fun (name, op) ->
+      ( name
+      , (let+ x = String_with_vars.decode
+         and+ y = String_with_vars.decode
+         in
+         Compare (op, x, y))))
+  in
+  let decode =
+    fix begin fun t ->
+      if_list
+        ~then_:(
+          [ "or", repeat t >>| (fun x -> Or x)
+          ; "and", repeat t >>| (fun x -> And x)
+          ] @ ops
+          |> sum)
+        ~else_:(String_with_vars.decode >>| fun v -> Expr v)
+    end
+  in
+  let+ () = Syntax.since Stanza.syntax (1, 1)
+  and+ decode = decode
+  in
+  decode

src/blang.mli

@@ -22,5 +22,9 @@ val true_ : t
 val eval
   :  t
   -> dir:Path.t
-  -> f:Value.t list option  String_with_vars.expander
+  -> f:Value.t list option String_with_vars.expander
   -> bool
+
+val to_dyn : t -> Dyn.t
+
+val decode : t Stanza.Decoder.t

src/dune_file.ml

@@ -319,43 +319,6 @@ module Preprocess = struct
               ]))
 end
 
-module Blang = struct
-  include Blang
-
-  let ops =
-    [ "=", Op.Eq
-    ; ">=", Gte
-    ; "<=", Lt
-    ; ">", Gt
-    ; "<", Lt
-    ; "<>", Neq
-    ]
-
-  let decode =
-    let ops =
-      List.map ops ~f:(fun (name, op) ->
-        ( name
-        , (let+ x = String_with_vars.decode
-           and+ y = String_with_vars.decode
-           in
-           Compare (op, x, y))))
-    in
-    let decode =
-      fix begin fun t ->
-        if_list
-          ~then_:(
-            [ "or", repeat t >>| (fun x -> Or x)
-            ; "and", repeat t >>| (fun x -> And x)
-            ] @ ops
-            |> sum)
-          ~else_:(String_with_vars.decode >>| fun v -> Expr v)
-      end
-    in
-    let+ () = Syntax.since Stanza.syntax (1, 1)
-    and+ decode = decode
-    in
-    decode
-end
 
 let enabled_if =
   field "enabled_if" ~default:Blang.true_