import/utils: spdx-string->license: Support '+' operator.

Previously, '+' was supported only via special cases for deprecated
GNU identifiers like 'GPL-N+'.  This commit adds support
for other uses of '+', such as 'AFL-2.0+' and 'LPPL-1.0+'.

Strictly speaking, '+' is an operator, not part of the SPDX license
identifier, but it is useful to handle it here.

* guix/import/utils.scm (spdx-string->license): Support '+' operator.
* tests/import-utils.scm ("spdx-string->license"): Test it.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

2 files changed, 16 insertions, 11 deletions

diff --git a/guix/import/utils.scm b/guix/import/utils.scm
index 9944b606f3..d6b179b57c 100644
--- a/guix/import/utils.scm
+++ b/guix/import/utils.scm
@@ -139,10 +139,11 @@ of the string VERSION is replaced by the symbol 'version."
   ;; Please update guix/licenses.scm when modifying
   ;; this list to avoid mismatches.
   ;;
-  ;; "GPL-N+" has been deprecated in favour of "GPL-N-or-later".
-  ;; "GPL-N" has been deprecated in favour of "GPL-N-only"
-  ;; or "GPL-N-or-later" as appropriate.  Likewise for LGPL
-  ;; and AGPL.
+  ;; "GPL-N+" has been deprecated in favour of "GPL-N-or-later".  "GPL-N" has
+  ;; been deprecated in favour of "GPL-N-only" or "GPL-N-or-later" as
+  ;; appropriate.  Likewise for LGPL and AGPL.  However, we list the
+  ;; deprecated forms here (with and without the "+" operator) to get better
+  ;; results from old license expressions.
   '(("AGPL-1.0"                   . license:agpl1)
     ("AGPL-1.0-only"              . license:agpl1)
     ("AGPL-3.0"                   . license:agpl3)
@@ -255,10 +256,11 @@ of the string VERSION is replaced by the symbol 'version."
     ("Zlib"                       . license:zlib)))
 
 (define (spdx-string->license str)
-  "Convert STR, an SPDX license identifier, to a symbol like 'license:gpl3+
-giving the prefixed name of a license object exported from (guix licenses).
-Return #f if STR does not match any known SPDX license identifiers.  Per the
-SPDX specification, license identifiers are compared case-insensitively."
+  "Convert STR, an SPDX license identifier (possibly with a postfix +
+operator), to a symbol like 'license:gpl3+ giving the prefixed name of a
+license object exported from (guix licenses).  Return #f if STR does not match
+any known SPDX license identifiers.  Per the SPDX specification, license
+identifiers are compared case-insensitively."
   ;; https://spdx.github.io/spdx-spec/v2.3/SPDX-license-expressions/#d2-case-sensitivity
   ;; Operators AND, OR, and WITH are case-sensitive, but identifiers are
   ;; case-insensitive for matching, though the canonical case is used in URIs.
@@ -266,7 +268,10 @@ SPDX specification, license identifiers are compared case-insensitively."
     ((_ . license)
      license)
     (#f
-     #f)))
+     (and (string-suffix? "+" str)
+          ;; We try the form with the + to support deprecated identifiers for
+          ;; GNU licenses (see above).  Here, we handle other uses of +.
+          (spdx-string->license (string-drop-right str 1))))))
 
 (define (license->symbol license)
   "Convert LICENSE object to a prefixed symbol representing the variable the
diff --git a/tests/import-utils.scm b/tests/import-utils.scm
index ee5b16adb8..f50f730873 100644
--- a/tests/import-utils.scm
+++ b/tests/import-utils.scm
@@ -236,8 +236,8 @@ Differences are hard to spot, e.g. in CLOS vs. GOOPS."))
          (hidden-package? pkg))))
 
 (test-equal "spdx-string->license"
-  '(license:gpl3+ license:agpl3)
+  '(license:gpl3+ license:agpl3 license:gpl2+)
   (map spdx-string->license
-       '("GPL-3.0-oR-LaTeR" "AGPL-3.0")))
+       '("GPL-3.0-oR-LaTeR" "AGPL-3.0" "GPL-2.0+")))
 
 (test-end "import-utils")