[PATCH] import: pypi: Detect inputs.

[Cyril Roelandt]

* guix/import/pypi.scm (compute-inputs, guess-requirements): New procedures.
---
 guix/import/pypi.scm | 149 ++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 118 insertions(+), 31 deletions(-)

diff --git a/guix/import/pypi.scm b/guix/import/pypi.scm
index 8567cad..1091deb 100644
--- a/guix/import/pypi.scm
+++ b/guix/import/pypi.scm
@@ -21,6 +21,7 @@
   #:use-module (ice-9 match)
   #:use-module (ice-9 pretty-print)
   #:use-module (ice-9 regex)
+  #:use-module ((ice-9 rdelim) #:select (read-line))
   #:use-module (srfi srfi-1)
   #:use-module (rnrs bytevectors)
   #:use-module (json)
@@ -77,42 +78,128 @@ or #f on failure."
 with dashes."
   (string-join (string-split (string-downcase str) #\_) "-"))
 
-(define (guix-hash-url url)
-  "Download the resource at URL and return the hash in nix-base32 format."
-  (call-with-temporary-output-file
-   (lambda (temp port)
-     (and (url-fetch url temp)
-          (bytevector->nix-base32-string
-           (call-with-input-file temp port-sha256))))))
+(define (guix-hash-url filename)
+  "Return the hash of FILENAME in nix-base32 format."
+  (bytevector->nix-base32-string
+   (call-with-input-file filename port-sha256)))
+
+(define (guix-name name)
+  (if (string-prefix? "python-" name)
+      (snake-case name)
+      (string-append "python-" (snake-case name))))
+
+(define (maybe-inputs guix-name inputs)
+  (match inputs
+    (()
+     '())
+    ((inputs ...)
+     `((,guix-name (,'quasiquote ,inputs))))))
+
+(define (guess-requirements source-url tarball)
+  "Given SOURCE-URL and a TARBALL of the package, return a list of the required
+packages specified in the requirements.txt file."
+
+  (define (tarball-directory url)
+    "Given the URL of the package's tarball, return the name of the directory
+that will be created upon decompressing it."
+    ;; TODO: Support more archive formats.
+    (let ((basename (substring url (+ 1 (string-rindex url #\/)))))
+    (cond
+     ((string-suffix? ".tar.gz" basename)
+      (string-drop-right basename 7))
+     ((string-suffix? ".tar.bz2" basename)
+      (string-drop-right basename 8))
+     (else #f))))
+
+  (define (clean-requirement s)
+    "Given a requirement LINE, as can be found in a Python requirements.txt
+file, remove everything other than the actual name of the required package, and
+return it."
+    (string-take s
+     (or (string-index s (lambda (c)
+                         (member c '(#\< #\> #\= #\#))))
+         (string-length s))))
+
+  (define (comment? line)
+    "Return #t if the given LINE is a comment, #f otherwise."
+    (eq? (string-ref line 0) #\#))
+
+  (define (read-requirements requirements-file)
+    "Given REQUIREMENTS-FILE, a Python requirements.txt file, return a list of
+name/variable pairs describing the requirements."
+    (call-with-input-file requirements-file
+      (lambda (port)
+        (let loop ((result '()))
+          (let ((line (read-line port)))
+            (if (eof-object? line)
+                result
+                (cond
+                 ((or (string-null? line) (comment? line))
+                  (loop result))
+                 (else
+                  (loop (cons (guix-name (clean-requirement line))
+                              result))))))))))
+
+  (let ((dirname (tarball-directory source-url)))
+    (if (string? dirname)
+        (let ((req-file (string-append dirname "/requirements.txt")))
+          ;; TODO: support more formats.
+          (if (zero? (system* "tar" "xf" tarball req-file))
+              (dynamic-wind
+                (const #t)
+                (lambda ()
+                  (read-requirements req-file))
+                (lambda ()
+                  (delete-file req-file)
+                  (rmdir dirname)))
+              '()))
+        '())))
+
+(define (compute-inputs source-url tarball)
+  "Given the SOURCE-URL of an already downloaded TARBALL, return a list of
+name/variable pairs describing the required inputs of this package."
+  (sort
+    (map (lambda (input)
+           (list input (list 'unquote (string->symbol input))))
+         (append '("python-setuptools")
+                 ;; Argparse has been part of Python since 2.7.
+                 (filter (lambda (input)
+                           (not (string=? "python-argparse" input)))
+                         (guess-requirements source-url tarball))))
+    (lambda args
+      (match args
+        (((a _ ...) (b _ ...))
+         (string-ci<? a b))))))
 
 (define (make-pypi-sexp name version source-url home-page synopsis
                         description license)
   "Return the `package' s-expression for a python package with the given NAME,
 VERSION, SOURCE-URL, HOME-PAGE, SYNOPSIS, DESCRIPTION, and LICENSE."
-  `(package
-     (name ,(if (string-prefix? "python-" name)
-                (snake-case name)
-                (string-append "python-" (snake-case name))))
-     (version ,version)
-     (source (origin
-               (method url-fetch)
-               (uri (string-append ,@(factorize-uri source-url version)))
-               (sha256
-                (base32
-                 ,(guix-hash-url source-url)))))
-     (build-system python-build-system)
-     (inputs
-      `(("python-setuptools" ,python-setuptools)))
-     (home-page ,home-page)
-     (synopsis ,synopsis)
-     (description ,description)
-     (license ,(assoc-ref `((,lgpl2.0 . lgpl2.0)
-                            (,gpl3 . gpl3)
-                            (,bsd-3 . bsd-3)
-                            (,expat . expat)
-                            (,public-domain . public-domain)
-                            (,asl2.0 . asl2.0))
-                          license))))
+  (call-with-temporary-output-file
+   (lambda (temp port)
+     (and (url-fetch source-url temp)
+          `(package
+             (name ,(guix-name name))
+             (version ,version)
+             (source (origin
+                       (method url-fetch)
+                       (uri (string-append ,@(factorize-uri source-url 
version)))
+                       (sha256
+                        (base32
+                         ,(guix-hash-url temp)))))
+             (build-system python-build-system)
+             ,@(maybe-inputs 'inputs
+                (compute-inputs source-url temp))
+             (home-page ,home-page)
+             (synopsis ,synopsis)
+             (description ,description)
+             (license ,(assoc-ref `((,lgpl2.0 . lgpl2.0)
+                                    (,gpl3 . gpl3)
+                                    (,bsd-3 . bsd-3)
+                                    (,expat . expat)
+                                    (,public-domain . public-domain)
+                                    (,asl2.0 . asl2.0))
+                                  license)))))))
 
 (define (pypi->guix-package package-name)
   "Fetch the metadata for PACKAGE-NAME from pypi.python.org, and return the
-- 
1.8.4.rc3