import: crate: Use existing package satisfying semver requirement.

If a package satisfying the dependency's semver requirement already exists,
use it. Prior to this change the highest version matching the semver
requirement was used (and imported in case it was not defined as package
already).

When resolving a dependency (now done in `sort-map-dependencies`), first
search for a package matching the semver requirement and only if this fails
reach out for a crate.

* guix/import/crate.scm (crate->guix-package)[find-package-version]: New
  function. [dependency-name+version]: New function.
  [sort-map-dependencies]: Use it instead of lambda function.

* tests/crate.scm (test-doctool-crate, test-doctool-dependencies): New
  variables.
  ("self-test …", "cargo-recursive-import-hoors-existing-packages"): New
  tests.

guix/import/crate.scm

@@ -32,6 +32,7 @@
   #:use-module (guix packages)
   #:use-module (guix upstream)
   #:use-module (guix utils)
+  #:use-module (gnu packages)
   #:use-module (ice-9 match)
   #:use-module (ice-9 regex)
   #:use-module (json)
@@ -92,7 +93,7 @@
   (requirement   crate-dependency-requirement "req")) ;string
 
 (module-autoload! (current-module)
-		  '(semver) '(string->semver semver<?))
+		  '(semver) '(string->semver semver->string semver<?))
 (module-autoload! (current-module)
 		  '(semver ranges) '(string->semver-range semver-range-contains?))
 
@@ -235,6 +236,21 @@ look up the development dependencs for the given crate."
          (or version
              (crate-latest-version crate))))
 
+  ;; find the highest existing package that fulfills the semver <range>
+  (define (find-package-version name range)
+    (let* ((semver-range (string->semver-range range))
+           (versions
+            (sort
+             (filter (lambda (version)
+                       (semver-range-contains? semver-range version))
+                     (map (lambda (pkg)
+                            (string->semver (package-version pkg)))
+                          (find-packages-by-name
+                           (crate-name->package-name name))))
+             semver<?)))
+      (and (not (null-list? versions))
+           (semver->string (last versions)))))
+
   ;; find the highest version of a crate that fulfills the semver <range>
   (define (find-crate-version crate range)
     (let* ((semver-range (string->semver-range range))
@@ -251,6 +267,17 @@ look up the development dependencs for the given crate."
       (and (not (null-list? versions))
            (second (last versions)))))
 
+  (define (dependency-name+version dep)
+    (let* ((name (crate-dependency-id dep))
+           (req (crate-dependency-requirement dep))
+           (existing-version (find-package-version name req)))
+      (if existing-version
+          (list name existing-version)
+          (let* ((crate (lookup-crate* name))
+                 (ver (find-crate-version crate req)))
+            (list name
+                  (crate-version-number ver))))))
+
   (define version*
     (and crate
          (find-crate-version crate version-number)))
@@ -258,13 +285,7 @@ look up the development dependencs for the given crate."
   ;; sort and map the dependencies to a list containing
   ;; pairs of (name version)
   (define (sort-map-dependencies deps)
-    (sort (map (lambda (dep)
+    (sort (map dependency-name+version
-                 (let* ((name (crate-dependency-id dep))
-                        (crate (lookup-crate* name))
-                        (req (crate-dependency-requirement dep))
-                        (ver (find-crate-version crate req)))
-                   (list name
-                         (crate-version-number ver))))
                deps)
           (match-lambda* (((name _) ...)
                           (apply string-ci<? name)))))

tests/crate.scm

@@ -25,6 +25,7 @@
   #:use-module (guix build-system cargo)
   #:use-module (gcrypt hash)
   #:use-module (guix tests)
+  #:use-module (gnu packages)
   #:use-module (ice-9 iconv)
   #:use-module (ice-9 match)
   #:use-module (srfi srfi-64))
@@ -312,6 +313,7 @@
   \"dependencies\": []
 }")
 
+
 (define test-source-hash
   "")
 
@@ -572,4 +574,85 @@
   '(license:expat license:asl2.0)
   (string->license "MIT/Apache-2.0"))
 
+
+
+(define test-doctool-crate
+  "{
+  \"crate\": {
+    \"max_version\": \"2.2.2\",
+    \"name\": \"leaf-bob\",
+    \"description\": \"summary\",
+    \"homepage\": \"http://example.com\",
+    \"repository\": \"http://example.com\",
+    \"keywords\": [\"dummy\", \"test\"],
+    \"categories\": [\"test\"]
+    \"actual_versions\": [
+      { \"id\": 234280,
+        \"num\": \"2.2.2\",
+        \"license\": \"MIT OR Apache-2.0\",
+        \"links\": {
+          \"dependencies\": \"/api/v1/crates/doctool/2.2.2/dependencies\"
+        }
+      }
+    ]
+  }
+}")
+
+;; FIXME: This test depends on some existing packages
+(define test-doctool-dependencies
+  "{
+  \"dependencies\": [
+     {
+       \"crate_id\": \"docopt\",
+       \"kind\": \"normal\",
+       \"req\": \"^0.8.1\"
+     }
+  ]
+}")
+
+
+(test-assert "self-test: rust-docopt 0.8.x is gone, please adjust the test case"
+  (not (null? (find-packages-by-name "rust-docopt" "0.8"))))
+
+(test-assert "cargo-recursive-import-hoors-existing-packages"
+  (mock ((guix http-client) http-fetch
+         (lambda (url . rest)
+           (match url
+             ("https://crates.io/api/v1/crates/doctool"
+              (open-input-string test-doctool-crate))
+             ("https://crates.io/api/v1/crates/doctool/2.2.2/download"
+              (set! test-source-hash
+                    (bytevector->nix-base32-string
+                     (sha256 (string->bytevector "empty file\n" "utf-8"))))
+              (open-input-string "empty file\n"))
+             ("https://crates.io/api/v1/crates/doctool/2.2.2/dependencies"
+              (open-input-string test-doctool-dependencies))
+             (_ (error "Unexpected URL: " url)))))
+        (match (crate-recursive-import "doctool")
+          (((define-public 'rust-doctool-2
+              (package
+                (name "rust-doctool")
+                (version "2.2.2")
+                (source
+                 (origin
+                   (method url-fetch)
+                   (uri (crate-uri "doctool" version))
+                   (file-name
+                    (string-append name "-" version ".tar.gz"))
+                   (sha256
+                    (base32
+                     (?  string? hash)))))
+                (build-system cargo-build-system)
+                (arguments
+                 ('quasiquote (#:cargo-inputs
+                               (("rust-docopt"
+                                 ('unquote 'rust-docopt-0.8))))))
+                (home-page "http://example.com")
+                (synopsis "summary")
+                (description "summary")
+                (license (list license:expat license:asl2.0)))))
+            #t)
+          (x
+           (pk 'fail x #f)))))
+
 (test-end "crate")