import: pypi: Detect inputs.

* guix/import/pypi.scm (python->package-name, maybe-inputs, compute-inputs,
  guess-requirements): New procedures.
* guix/import/pypi.scm (guix-hash-url): Now takes a filename instead of an
  URL as input.
* guix/import/pypi.scm (make-pypi-sexp): Now tries to generate the inputs
  automagically.
* tests/pypi.scm: Update the test.

guix/import/pypi.scm

@@ -21,10 +21,13 @@
   #: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 (srfi srfi-26)
   #:use-module (rnrs bytevectors)
   #:use-module (json)
   #:use-module (web uri)
+  #:use-module (guix ui)
   #:use-module (guix utils)
   #:use-module (guix import utils)
   #:use-module (guix import json)
@@ -77,32 +80,127 @@ or #f on failure."
 with dashes."
   (string-join (string-split (string-downcase str) #\_) "-"))
 
-(define (guix-hash-url url)
+(define (guix-hash-url filename)
-  "Download the resource at URL and return the hash in nix-base32 format."
+  "Return the hash of FILENAME in nix-base32 format."
-  (call-with-temporary-output-file
+  (bytevector->nix-base32-string  (file-sha256 filename)))
-   (lambda (temp port)
+
-     (and (url-fetch url temp)
+(define (python->package-name name)
-          (bytevector->nix-base32-string
+  "Given the NAME of a package on PyPI, return a Guix-compliant name for the
-           (call-with-input-file temp port-sha256))))))
+package."
+  (if (string-prefix? "python-" name)
+      (snake-case name)
+      (string-append "python-" (snake-case name))))
+
+(define (maybe-inputs package-inputs)
+  "Given a list of PACKAGE-INPUTS, tries to generate the 'inputs' field of a
+package definition."
+  (match package-inputs
+    (()
+     '())
+    ((package-inputs ...)
+     `((inputs (,'quasiquote ,package-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. TARBALL will be extracted in
+the current directory, and will be deleted."
+
+  (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. If the filetype is not
+    ;; supported, return #f.
+    ;; 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
+        (begin
+          (warning (_ "Unsupported archive format: \
+cannot determine package dependencies"))
+          #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 #\space)
+         (string-length s))))
+
+  (define (comment? line)
+    ;; Return #t if the given LINE is a comment, #f otherwise.
+    (eq? (string-ref (string-trim 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 (python->package-name (clean-requirement line))
+                              result))))))))))
+
+  (let ((dirname (tarball-directory source-url)))
+    (if (string? dirname)
+        (let* ((req-file (string-append dirname "/requirements.txt"))
+               (exit-code (system* "tar" "xf" tarball req-file)))
+          ;; TODO: support more formats.
+          (if (zero? exit-code)
+              (dynamic-wind
+                (const #t)
+                (lambda ()
+                  (read-requirements req-file))
+                (lambda ()
+                  (delete-file req-file)
+                  (rmdir dirname)))
+              (begin
+                (warning (_ "tar xf failed with exit code ~a") exit-code)
+                '())))
+        '())))
+
+(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.
+                 (remove (cut string=? "python-argparse" <>)
+                         (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."
+  (call-with-temporary-output-file
+   (lambda (temp port)
+     (and (url-fetch source-url temp)
           `(package
-     (name ,(if (string-prefix? "python-" name)
+             (name ,(python->package-name 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)))))
+                         ,(guix-hash-url temp)))))
              (build-system python-build-system)
-     (inputs
+             ,@(maybe-inputs (compute-inputs source-url temp))
-      `(("python-setuptools" ,python-setuptools)))
              (home-page ,home-page)
              (synopsis ,synopsis)
              (description ,description)
@@ -112,7 +210,7 @@ VERSION, SOURCE-URL, HOME-PAGE, SYNOPSIS, DESCRIPTION, and LICENSE."
                                     (,expat . expat)
                                     (,public-domain . public-domain)
                                     (,asl2.0 . asl2.0))
-                          license))))
+                                  license)))))))
 
 (define (pypi->guix-package package-name)
   "Fetch the metadata for PACKAGE-NAME from pypi.python.org, and return the

tests/pypi.scm

@@ -21,6 +21,7 @@
   #:use-module (guix base32)
   #:use-module (guix hash)
   #:use-module (guix tests)
+  #:use-module ((guix build utils) #:select (delete-file-recursively))
   #:use-module (srfi srfi-64)
   #:use-module (ice-9 match))
 
@@ -46,8 +47,14 @@
   }
 }")
 
-(define test-source
+(define test-source-hash
-  "foobar")
+  "")
+
+(define test-requirements
+"# A comment
+ # A comment after a space
+bar
+baz > 13.37")
 
 (test-begin "pypi")
 
@@ -55,15 +62,22 @@
   ;; Replace network resources with sample data.
   (mock ((guix import utils) url-fetch
          (lambda (url file-name)
-           (with-output-to-file file-name
-             (lambda ()
-               (display
            (match url
              ("https://pypi.python.org/pypi/foo/json"
-                   test-json)
+              (with-output-to-file file-name
+                (lambda ()
+                  (display test-json))))
              ("https://example.com/foo-1.0.0.tar.gz"
-                   test-source)
+               (begin
-                  (_ (error "Unexpected URL: " url))))))))
+                 (mkdir "foo-1.0.0")
+                 (with-output-to-file "foo-1.0.0/requirements.txt"
+                   (lambda ()
+                     (display test-requirements)))
+                 (system* "tar" "czvf" file-name "foo-1.0.0/")
+                 (delete-file-recursively "foo-1.0.0")
+                 (set! test-source-hash
+                       (call-with-input-file file-name port-sha256))))
+             (_ (error "Unexpected URL: " url)))))
     (match (pypi->guix-package "foo")
       (('package
          ('name "python-foo")
@@ -78,13 +92,15 @@
          ('build-system 'python-build-system)
          ('inputs
           ('quasiquote
-           (("python-setuptools" ('unquote 'python-setuptools)))))
+           (("python-bar" ('unquote 'python-bar))
+            ("python-baz" ('unquote 'python-baz))
+            ("python-setuptools" ('unquote 'python-setuptools)))))
          ('home-page "http://example.com")
          ('synopsis "summary")
          ('description "summary")
          ('license 'lgpl2.0))
        (string=? (bytevector->nix-base32-string
-                  (call-with-input-string test-source port-sha256))
+                  test-source-hash)
                  hash))
       (x
        (pk 'fail x #f)))))