Add a lint check for SPDX licenses

and update the documentation.
Supersedes and closes #2224

doc/pages/Manual.md

@@ -787,8 +787,8 @@ files.
   a list of strings listing the original authors of the software.
 
 - <a id="opamfield-license">`license: [ <string> ... ]`</a>:
-  the abbreviated name(s) of the license(s) under which the source software is
-  available.
+  The SPDX ID of the license(s) under which the source software is available
+  (see http://spdx.org/licenses/).
 
 - <a id="opamfield-homepage">`homepage: [ <string> ... ]`</a>,
   <a id="opamfield-doc">`doc: [ <string> ... ]`</a>,

src/state/dune

@@ -14,3 +14,33 @@
   (targets opamScript.ml)
   (deps    ../../shell/crunch.ml (glob_files shellscripts/*.*sh))
   (action  (with-stdout-to %{targets} (run ocaml %{deps}))))
+
+
+;; These rules are here to document and for easy (re-)generation of the module,
+;; but relying on the checked-in file should be OK (we don't want to rely on
+;; either `jq` or a network download). Hence the `(mode fallback)`.
+(rule
+  (targets opamSpdxList.ml)
+  (mode fallback)
+  (action (with-stdout-to %{targets}
+    (progn
+      (echo "(* THIS FILE IS GENERATED. See dune file *)\n\n")
+      (echo "open OpamCompat\n")
+      (echo "let licenses = OpamStd.String.Set.of_list @@ List.map String.lowercase_ascii @@ [\n")
+      (cat spdx-license-list)
+      (echo "]\n")
+      (echo "let exceptions = OpamStd.String.Set.of_list @@ List.map String.lowercase_ascii @@ [\n")
+      (cat spdx-license-exn-list)
+      (echo "]\n")))))
+(rule
+  (targets spdx-license-list)
+  (action  (with-stdout-to %{targets}
+    (system
+      "curl https://raw.githubusercontent.com/spdx/license-list-data/master/json/licenses.json |
+       jq -rc '.licenses | map(\"  \\\"\" + .licenseId + \"\\\";\") | join(\"\\n\")'"))))
+(rule
+  (targets spdx-license-exn-list)
+  (action  (with-stdout-to %{targets}
+    (system
+      "curl https://raw.githubusercontent.com/spdx/license-list-data/master/json/exceptions.json |
+       jq -rc '.exceptions | map(\"  \\\"\" + .licenseExceptionId + \"\\\";\") | join(\"\\n\")'"))))

src/state/opamFileTools.ml

@@ -16,6 +16,17 @@ let log fmt = OpamConsole.log "opam-file" fmt
 
 open OpamFile.OPAM
 
+let is_valid_license_id s =
+  let memplus s =
+    let s = OpamStd.String.remove_suffix ~suffix:"+" s in
+    OpamStd.String.Set.mem s OpamSpdxList.licenses
+  in
+  match OpamStd.String.split (String.lowercase_ascii s) ' ' with
+  | [s] -> memplus s
+  | [s; "with"; e] ->
+    memplus s && OpamStd.String.Set.mem e OpamSpdxList.exceptions
+  | _ -> false
+
 (** manipulation utilities *)
 
 let names_of_formula flag f =
@@ -686,6 +697,13 @@ let t_lint ?check_extra_files ?(check_upstream=false) ?(all=false) t =
      cond 61 `Warning
        "`with-test` variable in `run-test` is out of scope, it will be ignored"
        with_test);
+    (let bad_licenses =
+       List.filter (fun s -> not (is_valid_license_id s)) t.license
+     in
+     cond 62 `Warning
+       "License doesn't adhere to the SPDX standard, see https://spdx.org/licenses/"
+       ~detail:bad_licenses
+       (bad_licenses <> []));
   ]
   in
   format_errors @