[bug#48999] [PATCH v2 1/3] import: hackage: Accept local source for package.

[Xinglu Chen <public@yoctocell.xyz>]

When developing a Haskell package it is often useful to have a Guix package
definition for that package, previously one would have to write that package
definition by hand, and if the .cabal file changed one would manually update
the Guix package definition.

This commit allows one to specify a custom source for their package, meaning
that one could programatically generate a Guix package definition for their
local Haskell package.  If the .cabal file changes, the generated package
definition will also change accordingly.  One could for instance write the
following in a guix.scm file:

  (define-values (ghc-haskeme deps)
    (call-with-input-file "haskeme.cabal"
      (lambda (port)
        (hackage->guix-package
         "haskeme"
         #:port port
         #:source (local-file "." "haskeme-checkout"
                              #:recursive? #t
                              #:select? hg-predicate)))))

  ghc-haskeme

Invoking ‘guix build -f guix.scm’ would then always build an up-to-date
version of the package.

* guix/import/hackage.scm (hackage-module->sexp): Add optional keyword
argument ‘source’
(hackage->guix-package): Likewise.
* tests/hackage.scm (eval-test-with-cabal): Likewise.
("hackage->guix-package local source"): New test.
---
 guix/import/hackage.scm | 43 ++++++++++++++++++++++++++---------------
 tests/hackage.scm       | 28 +++++++++++++++++++++++++--
 2 files changed, 53 insertions(+), 18 deletions(-)

diff --git a/guix/import/hackage.scm b/guix/import/hackage.scm
index f94a1e7087..326ab92365 100644
--- a/guix/import/hackage.scm
+++ b/guix/import/hackage.scm
@@ -227,10 +227,13 @@ package being processed and is used to filter references to itself."
           dependencies))
 
 (define* (hackage-module->sexp cabal cabal-hash
-                               #:key (include-test-dependencies? #t))
+                               #:key
+                               (include-test-dependencies? #t)
+                               (source #f))
   "Return the `package' S-expression for a Cabal package.  CABAL is the
-representation of a Cabal file as produced by 'read-cabal'.  CABAL-HASH is
-the hash of the Cabal file."
+representation of a Cabal file as produced by 'read-cabal'.  CABAL-HASH is the
+hash of the Cabal file.  If SOURCE is specified, it will be used as the source
+for the package."
 
   (define name
     (cabal-package-name cabal))
@@ -294,20 +297,24 @@ the hash of the Cabal file."
       (() '())
       (args `((arguments (,'quasiquote ,args))))))
 
-  (let ((tarball (with-store store
-                   (download-to-store store source-url))))
+  (let ((tarball (if source
+                     #f
+                     (with-store store
+                       (download-to-store store source-url)))))
     (values
      `(package
         (name ,(hackage-name->package-name name))
         (version ,version)
-        (source (origin
-                  (method url-fetch)
-                  (uri (string-append ,@(factorize-uri source-url version)))
-                  (sha256
-                   (base32
-                    ,(if tarball
-                         (bytevector->nix-base32-string (file-sha256 tarball))
-                         "failed to download tar archive")))))
+        (source ,(if source
+                     source
+                     `(origin
+                        (method url-fetch)
+                        (uri (string-append ,@(factorize-uri source-url version)))
+                        (sha256
+                         (base32
+                          ,(if tarball
+                               (bytevector->nix-base32-string (file-sha256 tarball))
+                               "failed to download tar archive"))))))
         (build-system haskell-build-system)
         ,@(maybe-inputs 'inputs dependencies)
         ,@(maybe-inputs 'native-inputs native-dependencies)
@@ -321,10 +328,12 @@ the hash of the Cabal file."
 (define* (hackage->guix-package package-name #:key
                                 (include-test-dependencies? #t)
                                 (port #f)
+                                (source #f)
                                 (cabal-environment '()))
   "Fetch the Cabal file for PACKAGE-NAME from hackage.haskell.org, or, if the
-called with keyword parameter PORT, from PORT.  Return the `package'
-S-expression corresponding to that package, or #f on failure.
+called with keyword parameter PORT, from PORT.  If SOURCE is specified, use it
+as the source for the package instead of trying to fetch a tarball.  Return
+the `package' S-expression corresponding to that package, or #f on failure.
 CABAL-ENVIRONMENT is an alist defining the environment in which the Cabal
 conditionals are evaluated.  The accepted keys are: \"os\", \"arch\", \"impl\"
 and the name of a flag.  The value associated with a flag has to be either the
@@ -338,7 +347,9 @@ respectively."
                     (hackage-fetch-and-hash package-name))))
     (and=> cabal-meta (compose (cut hackage-module->sexp <> cabal-hash
                                     #:include-test-dependencies?
-                                    include-test-dependencies?)
+                                    include-test-dependencies?
+                                    #:source
+                                    source)
                                (cut eval-cabal <> cabal-environment)))))
 
 (define hackage->guix-package/m                   ;memoized variant
diff --git a/tests/hackage.scm b/tests/hackage.scm
index 53972fc643..3083a5d4df 100644
--- a/tests/hackage.scm
+++ b/tests/hackage.scm
@@ -22,6 +22,7 @@
   #:use-module (guix import cabal)
   #:use-module (guix import hackage)
   #:use-module (guix tests)
+  #:use-module (guix gexp)
   #:use-module (srfi srfi-64)
   #:use-module (ice-9 match))
 
@@ -186,9 +187,28 @@ library
     ('description (? string?))
     ('license 'license:bsd-3)))
 
-(define* (eval-test-with-cabal test-cabal matcher #:key (cabal-environment '()))
+(define-package-matcher match-ghc-foo-local-source
+  ('package
+    ('name "ghc-foo")
+    ('version "1.0.0")
+    ('source
+     (? file-like?))
+    ('build-system 'haskell-build-system)
+    ('inputs
+     ('quasiquote
+      (("ghc-http" ('unquote 'ghc-http)))))
+    ('home-page "http://test.org")
+    ('synopsis (? string?))
+    ('description (? string?))
+    ('license 'license:bsd-3)))
+
+(define* (eval-test-with-cabal test-cabal matcher
+                               #:key (cabal-environment '()) (source #f))
   (define port (open-input-string test-cabal))
-  (matcher (hackage->guix-package "foo" #:port port #:cabal-environment cabal-environment)))
+  (matcher (hackage->guix-package "foo"
+                                  #:port port
+                                  #:cabal-environment cabal-environment
+                                  #:source source)))
 
 (test-assert "hackage->guix-package test 1"
   (eval-test-with-cabal test-cabal-1 match-ghc-foo))
@@ -208,6 +228,10 @@ library
   (eval-test-with-cabal test-cabal-5 match-ghc-foo
                         #:cabal-environment '(("impl" . "ghc-7.8"))))
 
+(test-assert "hackage->guix-package local source"
+  (eval-test-with-cabal test-cabal-1 match-ghc-foo-local-source
+                        #:source (plain-file "dummy source" "source")))
+
 (define-package-matcher match-ghc-foo-6
   ('package
     ('name "ghc-foo")
-- 
2.32.0