import: crate: Better handle license expressions.

* guix/import/crate.scm (%dual-license-rx): Removed function.
(crate->guix-package): Handle most of the multi-licensing cases.
* tests/crate.scm (licenses): Add tests for some licenses.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

guix/import/crate.scm

@@ -178,21 +178,20 @@ (define* (make-crate-sexp #:key name version cargo-inputs cargo-development-inpu
          (close-port port)
          pkg))
 
-(define %dual-license-rx
-  ;; Dual licensing is represented by a string such as "MIT OR Apache-2.0".
-  ;; This regexp matches that.
-  (make-regexp "^(.*) OR (.*)$"))
+(define (string->license string)
+  (filter-map (lambda (license)
+                (and (not (string-null? license))
+                     (not (any (lambda (elem) (string=? elem license))
+                               '("AND" "OR" "WITH")))
+                     (or (spdx-string->license license)
+                         'unknown-license!)))
+              (string-split string (string->char-set " /"))))
 
 (define* (crate->guix-package crate-name #:optional version)
   "Fetch the metadata for CRATE-NAME from crates.io, and return the
 `package' s-expression corresponding to that package, or #f on failure.
 When VERSION is specified, attempt to fetch that version; otherwise fetch the
 latest version of CRATE-NAME."
-  (define (string->license string)
-    (match (regexp-exec %dual-license-rx string)
-      (#f (list (spdx-string->license string)))
-      (m  (list (spdx-string->license (match:substring m 1))
-                (spdx-string->license (match:substring m 2))))))
 
   (define (normal-dependency? dependency)
     (eq? (crate-dependency-kind dependency) 'normal))

tests/crate.scm

@@ -233,6 +233,9 @@ (define test-leaf-bob-dependencies
 (define test-source-hash
   "")
 
+(define string->license
+  (@@ (guix import crate) string->license))
+
 (test-begin "crate")
 
 (test-equal "guix-package->crate-name"
@@ -437,4 +440,24 @@ (define test-source-hash
           (x
            (pk 'fail x #f)))))
 
+(test-equal "licenses: MIT OR Apache-2.0"
+  '(license:expat license:asl2.0)
+  (string->license "MIT OR Apache-2.0"))
+
+(test-equal "licenses: Apache-2.0 / MIT"
+  '(license:asl2.0 license:expat)
+  (string->license "Apache-2.0 / MIT"))
+
+(test-equal "licenses: Apache-2.0 WITH LLVM-exception"
+  '(license:asl2.0 unknown-license!)
+  (string->license "Apache-2.0 WITH LLVM-exception"))
+
+(test-equal "licenses: MIT/Apache-2.0 AND BSD-2-Clause"
+  '(license:expat license:asl2.0 unknown-license!)
+  (string->license "MIT/Apache-2.0 AND BSD-2-Clause"))
+
+(test-equal "licenses: MIT/Apache-2.0"
+  '(license:expat license:asl2.0)
+  (string->license "MIT/Apache-2.0"))
+
 (test-end "crate")