import: hackage: Parse braced properties.

This adds partial support for Cabal properties that use curly
braces instead of the layout rule.  See for example
https://hackage.haskell.org/package/cassava/

* guix/import/cabal.scm (read-braced-value): New procedure.
(is-property): Remove.
(is-layout-property, is-braced-property): New variables.
(lex-property): Rename to...
(lex-layout-property): ... this.
(lex-braced-property, lex-property): New procedures.
(lex-token): Add call to 'lex-property'.
* guix/tests/hackage.scm: Test braced description import.
* tests/hackage.scm (test-cabal-multiline-desc): Rename to...
(test-cabal-multiline-layout): ... this.
("hackage->guix-package test multiline desc"): Rename to...
("hackage->guix-package test multiline desc (layout)"): ... this.
(test-cabal-multiline-braced): New variable.
("hackage->guix-package test multiline desc (braced)"): New test.

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

guix/import/cabal.scm

@@ -270,6 +270,10 @@ following lines with indentation larger than MIN-INDENT."
                 (peek-next-line-indent port)))
         val)))
 
+(define* (read-braced-value port)
+  "Read up to a closing brace."
+  (string-trim-both (read-delimited "}" port 'trim)))
+
 (define (lex-white-space port bol)
   "Consume white spaces and comment lines on PORT.  If a new line is started return #t,
 otherwise return BOL (beginning-of-line)."
@@ -343,7 +347,10 @@ matching a string against the created regexp."
                 (make-regexp pat))))
     (cut regexp-exec rx <>)))
 
-(define is-property (make-rx-matcher "([a-z0-9-]+)[ \t]*:[ \t]*(\\w?.*)$"
+(define is-layout-property (make-rx-matcher "([a-z0-9-]+)[ \t]*:[ \t]*(\\w?[^{}]*)$"
+                                            regexp/icase))
+
+(define is-braced-property (make-rx-matcher "([a-z0-9-]+)[ \t]*:[ \t]*\\{[ \t]*$"
                                             regexp/icase))
 
 (define is-flag (make-rx-matcher "^flag +([a-z0-9_-]+)"
@@ -435,13 +442,19 @@ string with the read characters."
                  (begin (unread-char c) (list->string res)))))
           (else (list->string res)))))
 
-(define (lex-property k-v-rx-res loc port)
+(define (lex-layout-property k-v-rx-res loc port)
   (let ((key (string-downcase (match:substring k-v-rx-res 1)))
         (value (match:substring k-v-rx-res 2)))
     (make-lexical-token
      'PROPERTY loc
      (list key `(,(read-value port value (current-indentation)))))))
 
+(define (lex-braced-property k-rx-res loc port)
+  (let ((key (string-downcase (match:substring k-rx-res 1))))
+    (make-lexical-token
+     'PROPERTY loc
+     (list key `(,(read-braced-value port))))))
+
 (define (lex-rx-res rx-res token loc)
   (let ((name (string-downcase (match:substring rx-res 1))))
     (make-lexical-token token loc name)))
@@ -552,7 +565,6 @@ LOC is the current port location."
 the current port location."
   (let* ((s (read-delimited "\n{}" port 'peek)))
     (cond
-     ((is-property s) => (cut lex-property <> loc port))
      ((is-flag s) => (cut lex-flag <> loc))
      ((is-src-repo s) => (cut lex-src-repo <> loc))
      ((is-exec s) => (cut lex-exec <> loc))
@@ -561,13 +573,22 @@ the current port location."
      ((is-benchmark s) => (cut lex-benchmark <> loc))
      ((is-lib s) (lex-lib loc))
      ((is-else s) (lex-else loc))
-     (else
+     (else (unread-string s port) #f))))
-      #f))))
+
+(define (lex-property port loc)
+  (let* ((s (read-delimited "\n" port 'peek)))
+    (cond
+      ((is-braced-property s) => (cut lex-braced-property <> loc port))
+      ((is-layout-property s) => (cut lex-layout-property <> loc port))
+      (else #f))))
 
 (define (lex-token port)
   (let* ((loc (make-source-location (cabal-file-name) (port-line port)
                                     (port-column port) -1 -1)))
-    (or (lex-single-char port loc) (lex-word port loc) (lex-line port loc))))
+    (or (lex-single-char port loc)
+        (lex-word port loc)
+        (lex-line port loc)
+        (lex-property port loc))))
 
 ;; Lexer- and error-function generators
 

tests/hackage.scm

@@ -237,7 +237,7 @@ library
   (eval-test-with-cabal test-cabal-6 match-ghc-foo-6))
 
 ;; Check multi-line layouted description
-(define test-cabal-multiline-desc
+(define test-cabal-multiline-layout
   "name: foo
 version: 1.0.0
 homepage: http://test.org
@@ -251,9 +251,28 @@ executable cabal
     mtl        >= 2.0      && < 3
 ")
 
-(test-assert "hackage->guix-package test multiline desc"
+(test-assert "hackage->guix-package test multiline desc (layout)"
-  (eval-test-with-cabal test-cabal-multiline-desc match-ghc-foo))
+  (eval-test-with-cabal test-cabal-multiline-layout match-ghc-foo))
 
+;; Check multi-line braced description
+(define test-cabal-multiline-braced
+  "name: foo
+version: 1.0.0
+homepage: http://test.org
+synopsis: synopsis
+description: {
+first line
+second line
+}
+license: BSD3
+executable cabal
+  build-depends:
+    HTTP       >= 4000.2.5 && < 4000.3,
+    mtl        >= 2.0      && < 3
+")
+
+(test-assert "hackage->guix-package test multiline desc (braced)"
+  (eval-test-with-cabal test-cabal-multiline-braced match-ghc-foo))
 
 (test-assert "read-cabal test 1"
   (match (call-with-input-string test-read-cabal-1 read-cabal)