[bug#35318] [PATCH] Update cargo-build-system to expand package inputs

[Ivan Petkov <ivanppetkov@gmail.com>]

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I’ve updated the patch series with the following improvements:

* I've applied any naming feedback which came from Ludo
* I've changed the cargo-build-system to only unpack inputs into the cargo
vendor directory if the following applies:
  - The input is a path to a gzip tarball
  - The archive contains a file called Cargo.toml at its root
  - This means that we no longer require crate sources to include a
  ".crate" extension

Whew, given that this has gotten pretty long, I'd be happy to land this as it
is for now (barring any blocking issues!), and iterating further going forward!

Thanks again to everyone for their feedback!
—Ivan


[-- Attachment #2: 0001-build-system-cargo-expand-transitive-crate-sources.patch --]
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From c063c354c02df84ae2a3aaad81175725622cc9d2 Mon Sep 17 00:00:00 2001
From: Ivan Petkov <ivanppetkov@gmail.com>
Date: Tue, 16 Apr 2019 03:37:44 -0700
Subject: [PATCH 1/7] build-system/cargo: expand transitive crate sources

* guix/build/cargo: (package-cargo-inputs): Add it.
(package-cargo-development-inputs): Add it.
(crate-clsoure): Add it.
(expand-crate-sources): Add it.
(lower): New cargo-inputs and cargo-development-inputs keywords.
Use expand-crate-sources.
(private-keywords): Add new keywords.
---
 guix/build-system/cargo.scm | 115 +++++++++++++++++++++++++++++++++++-
 1 file changed, 114 insertions(+), 1 deletion(-)

diff --git a/guix/build-system/cargo.scm b/guix/build-system/cargo.scm
index dc137421e9..828382678d 100644
--- a/guix/build-system/cargo.scm
+++ b/guix/build-system/cargo.scm
@@ -29,6 +29,8 @@
   #:use-module (guix build-system)
   #:use-module (guix build-system gnu)
   #:use-module (ice-9 match)
+  #:use-module (ice-9 vlist)
+  #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
   #:export (%cargo-build-system-modules
             %cargo-utils-modules
@@ -121,15 +123,125 @@ to NAME and VERSION."
                                 #:outputs (cons "src" outputs)
                                 #:guile-for-build guile-for-build))
 
+(define (package-cargo-inputs p)
+  (apply
+    (lambda* (#:key (cargo-inputs '()) #:allow-other-keys)
+      cargo-inputs)
+    (package-arguments p)))
+
+(define (package-cargo-development-inputs p)
+  (apply
+    (lambda* (#:key (cargo-development-inputs '()) #:allow-other-keys)
+      cargo-development-inputs)
+    (package-arguments p)))
+
+(define (crate-closure inputs)
+  "Return the closure of INPUTS when considering the 'cargo-inputs' and
+'cargod-dev-deps' edges.  Omit duplicate inputs, except for those
+already present in INPUTS itself.
+
+This is implemented as a breadth-first traversal such that INPUTS is
+preserved, and only duplicate extracted inputs are removed.
+
+Forked from ((guix packages) transitive-inputs) since this extraction
+uses slightly different rules compared to the rest of Guix (i.e. we
+do not extract the conventional inputs)."
+  (define (seen? seen item)
+    ;; FIXME: We're using pointer identity here, which is extremely sensitive
+    ;; to memoization in package-producing procedures; see
+    ;; <https://bugs.gnu.org/30155>.
+    (vhash-assq item seen))
+
+  (let loop ((inputs     inputs)
+             (result     '())
+             (propagated '())
+             (first?     #t)
+             (seen       vlist-null))
+    (match inputs
+      (()
+       (if (null? propagated)
+           (reverse result)
+           (loop (reverse (concatenate propagated)) result '() #f seen)))
+      (((and input (label (? package? package))) rest ...)
+       (if (and (not first?) (seen? seen package))
+           (loop rest result propagated first? seen)
+           (loop rest
+                 (cons input result)
+                 (cons (package-cargo-inputs package)
+                       propagated)
+                 first?
+                 (vhash-consq package package seen))))
+      ((input rest ...)
+       (loop rest (cons input result) propagated first? seen)))))
+
+(define (expand-crate-sources cargo-inputs cargo-development-inputs)
+  "Extract all transitive sources for CARGO-INPUTS and CARGO-DEVELOPMENT-INPUTS
+along their 'cargo-inputs' edges.
+
+Cargo requires all transitive crate dependencies' sources to be available
+in its index, even if they are optional (this is so it can generate
+deterministic Cargo.lock files regardless of the target platform or enabled
+features). Thus we need all transitive crate dependencies for any cargo
+dev-dependencies, but this is only needed when building/testing a crate directly
+(i.e. we will never need transitive dev-dependencies for any dependency crates).
+
+Another complication arises due potential dependency cycles from Guix's
+perspective: Although cargo does not permit cyclic dependencies between crates,
+however, it permits cycles to occur via dev-dependencies. For example, if crate
+X depends on crate Y, crate Y's tests could pull in crate X to to verify
+everything builds properly (this is a rare scenario, but it it happens for
+example with the `proc-macro2` and `quote` crates). This is allowed by cargo
+because tests are built as a pseudo-crate which happens to depend on the
+X and Y crates, forming an acyclic graph.
+
+We can side step this problem by only considering regular cargo dependencies
+since they are guaranteed to not have cycles. We can further resolve any
+potential dev-dependency cycles by extracting package sources (which never have
+any dependencies and thus no cycles can exist).
+
+There are several implications of this decision:
+* Building a package definition does not require actually building/checking
+any dependent crates. This can be a benefits:
+ - For example, sometimes a crate may have an optional dependency on some OS
+ specific package which cannot be built or run on the current system. This
+ approach means that the build will not fail if cargo ends up internally ignoring
+ the dependency.
+ - It avoids waiting for quadratic builds from source: cargo always builds
+ dependencies within the current workspace. This is largely due to Rust not
+ having a stable ABI and other resolutions that cargo applies. This means that
+ if we have a depencency chain of X -> Y -> Z and we build each definition
+ independently the following will happen:
+  * Cargo will build and test crate Z
+  * Cargo will build crate Z in Y's workspace, then build and test Y
+  * Cargo will build crates Y and Z in X's workspace, then build and test X
+* But there are also some downsides with this approach:
+  - If a dependent crate is subtly broken on the system (i.e. it builds but its
+  tests fail) the consuming crates may build and test successfully but
+  actually fail during normal usage (however, the CI will still build all
+  packages which will give visibility in case packages suddenly break).
+  - Because crates aren't declared as regular inputs, other Guix facilities
+  such as tracking package graphs may not work by default (however, this is
+  something that can always be extended or reworked in the future)."
+  (filter-map
+    (match-lambda
+      ((label (? package? p))
+       (list label (package-source p)))
+      ((label input)
+       (list label input)))
+    (crate-closure (append cargo-inputs cargo-development-inputs))))
+
 (define* (lower name
                 #:key source inputs native-inputs outputs system target
                 (rust (default-rust))
+                (cargo-inputs '())
+                (cargo-development-inputs '())
                 #:allow-other-keys
                 #:rest arguments)
   "Return a bag for NAME."
 
   (define private-keywords
-    '(#:source #:target #:rust #:inputs #:native-inputs #:outputs))
+    '(#:source #:target #:rust #:inputs #:native-inputs #:outputs
+      #:cargo-inputs #:cargo-development-inputs))
 
   (and (not target) ;; TODO: support cross-compilation
        (bag
@@ -145,6 +257,7 @@ to NAME and VERSION."
                         ,@(standard-packages)))
          (build-inputs `(("cargo" ,rust "cargo")
                          ("rustc" ,rust)
+                         ,@(expand-crate-sources cargo-inputs cargo-development-inputs)
                          ,@native-inputs))
          (outputs outputs)
          (build cargo-build)
-- 
2.21.0


[-- Attachment #3: 0002-build-system-cargo-use-sources-from-package-sources.patch --]
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From 93d8e04dc6d863213ad240ab11147a140bd665a9 Mon Sep 17 00:00:00 2001
From: Ivan Petkov <ivanppetkov@gmail.com>
Date: Thu, 16 May 2019 23:02:12 -0700
Subject: [PATCH 2/7] build-system/cargo: use sources from package sources

* guix/build/cargo-build-system: (configure): Expand crate tarballs in
vendor directory.
---
 guix/build/cargo-build-system.scm | 35 +++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/guix/build/cargo-build-system.scm b/guix/build/cargo-build-system.scm
index 9f44bd6ee9..b368074e8a 100644
--- a/guix/build/cargo-build-system.scm
+++ b/guix/build/cargo-build-system.scm
@@ -54,6 +54,22 @@
          (bin-dep? (lambda (dep) (find bin? (get-kinds dep)))))
     (find bin-dep? (manifest-targets))))
 
+(define (crate-src? path)
+  "Check if PATH refers to a crate source, namely a gzipped tarball with a
+Cargo.toml file present at its root."
+    (and (gzip-file? path)
+         ;; First we print out all file names within the tarball to see if it
+         ;; looks like the source of a crate. However, the tarball will include
+         ;; an extra path component which we would like to ignore (since we're
+         ;; interested in checking if a Cargo.toml exists at the root of the
+         ;; archive, but not nested anywhere else). We do this by cutting up
+         ;; each output line and only looking at the second component. We then
+         ;; check if it matches Cargo.toml exactly and short circuit if it does.
+         (zero? (apply system* (list "sh" "-c"
+                                     (string-append "tar -tf " path
+                                                    " | cut -d/ -f2"
+                                                    " | grep -q '^Cargo.toml$'"))))))
+
 (define* (configure #:key inputs
                     (vendor-dir "guix-vendor")
                     #:allow-other-keys)
@@ -67,14 +83,21 @@
   (for-each
     (match-lambda
       ((name . path)
-       (let* ((rust-share (string-append path "/share/rust-source"))
-              (basepath (basename path))
-              (link-dir (string-append vendor-dir "/" basepath)))
-         (and (file-exists? rust-share)
+       (let* ((basepath (basename path))
+              (crate-dir (string-append vendor-dir "/" basepath)))
+         (and (crate-src? path)
               ;; Gracefully handle duplicate inputs
-              (not (file-exists? link-dir))
-              (symlink rust-share link-dir)))))
+              (not (file-exists? crate-dir))
+              (mkdir-p crate-dir)
+              ;; Cargo crates are simply gzipped tarballs but with a .crate
+              ;; extension. We expand the source to a directory name we control
+              ;; so that we can generate any cargo checksums.
+              ;; The --strip-components argument is needed to prevent creating
+              ;; an extra directory within `crate-dir`.
+              (invoke "tar" "xvf" path "-C" crate-dir "--strip-components" "1")
+              (generate-checksums crate-dir)))))
     inputs)
+
   ;; Configure cargo to actually use this new directory.
   (mkdir-p ".cargo")
   (let ((port (open-file ".cargo/config" "w" #:encoding "utf-8")))
-- 
2.21.0


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From fec67a58e05588813bfc4808bd0792dd8f7564c6 Mon Sep 17 00:00:00 2001
From: Ivan Petkov <ivanppetkov@gmail.com>
Date: Thu, 16 May 2019 23:05:50 -0700
Subject: [PATCH 3/7] build-system/cargo: don't copy source as an output

* guix/build-system/cargo: (cargo-build)[build-expression->derivation]:
Don't add "src" output.
* guix/build/cargo-build-system: (install-source): Delete it.
(%standard-phases): Delete 'install-source.
---
 guix/build-system/cargo.scm       |  2 +-
 guix/build/cargo-build-system.scm | 19 -------------------
 2 files changed, 1 insertion(+), 20 deletions(-)

diff --git a/guix/build-system/cargo.scm b/guix/build-system/cargo.scm
index 828382678d..fa211d456d 100644
--- a/guix/build-system/cargo.scm
+++ b/guix/build-system/cargo.scm
@@ -120,7 +120,7 @@ to NAME and VERSION."
                                 #:inputs inputs
                                 #:system system
                                 #:modules imported-modules
-                                #:outputs (cons "src" outputs)
+                                #:outputs outputs
                                 #:guile-for-build guile-for-build))
 
 (define (package-cargo-inputs p)
diff --git a/guix/build/cargo-build-system.scm b/guix/build/cargo-build-system.scm
index b368074e8a..1f36304b15 100644
--- a/guix/build/cargo-build-system.scm
+++ b/guix/build/cargo-build-system.scm
@@ -140,24 +140,6 @@ directory = '" port)
 (define (touch file-name)
   (call-with-output-file file-name (const #t)))
 
-(define* (install-source #:key inputs outputs #:allow-other-keys)
-  "Install the source for a given Cargo package."
-  (let* ((out (assoc-ref outputs "out"))
-         (src (assoc-ref inputs "source"))
-         (rsrc (string-append (assoc-ref outputs "src")
-                              "/share/rust-source")))
-    (mkdir-p rsrc)
-    ;; Rust doesn't have a stable ABI yet. Because of this
-    ;; Cargo doesn't have a search path for binaries yet.
-    ;; Until this changes we are working around this by
-    ;; vendoring the crates' sources by symlinking them
-    ;; to store paths.
-    (copy-recursively "." rsrc)
-    (touch (string-append rsrc "/.cargo-ok"))
-    (generate-checksums rsrc)
-    (install-file "Cargo.toml" rsrc)
-    #t))
-
 (define* (install #:key inputs outputs skip-build? #:allow-other-keys)
   "Install a given Cargo package."
   (let* ((out (assoc-ref outputs "out")))
@@ -179,7 +161,6 @@ directory = '" port)
 (define %standard-phases
   (modify-phases gnu:%standard-phases
     (delete 'bootstrap)
-    (add-before 'configure 'install-source install-source)
     (replace 'configure configure)
     (replace 'build build)
     (replace 'check check)
-- 
2.21.0


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From 7d75538f8e24bb0dcbdd252a19ec68dd42947831 Mon Sep 17 00:00:00 2001
From: Ivan Petkov <ivanppetkov@gmail.com>
Date: Fri, 17 May 2019 09:07:54 -0700
Subject: [PATCH 4/7] doc: Update cargo-build-system parameter docs

* doc/guix.texi: (Build Systems)[cargo-build-system]: Add references to
the #:rust, #:cargo-inputs, and #:cargo-development-inputs parameters.
Remove reference to installing crate sources.
---
 doc/guix.texi | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index a9cd66ce87..61f5de9e5d 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -64,6 +64,7 @@ Copyright @copyright{} 2018 Laura Lazzati@*
 Copyright @copyright{} 2018 Alex Vong@*
 Copyright @copyright{} 2019 Josh Holland@*
 Copyright @copyright{} 2019 Diego Nicola Barbato@*
+Copyright @copyright{} 2019 Ivan Petkov@*
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -5814,10 +5815,20 @@ This variable is exported by @code{(guix build-system cargo)}.  It
 supports builds of packages using Cargo, the build tool of the
 @uref{https://www.rust-lang.org, Rust programming language}.
 
-In its @code{configure} phase, this build system replaces dependencies
-specified in the @file{Cargo.toml} file with inputs to the Guix package.
-The @code{install} phase installs the binaries, and it also installs the
-source code and @file{Cargo.toml} file.
+It adds @code{rustc} and @code{cargo} to the set of inputs.
+A different Rust package can be specified with the @code{#:rust} parameter.
+
+Regular cargo dependencies should be added to the package definition via
+the @code{#:cargo-inputs} parameter as a list of name and spec pairs, where the
+spec can be a package or a source definition. Note that the spec must evaluate
+to a path to a gzipped tarball which includes a @code{Cargo.toml} file at its
+root, or it will be ignored. Similarly, cargo dev-dependencies should be added
+to the package definition via the @code{#:cargo-development-inputs} parameter.
+
+In its @code{configure} phase, this build system will make any source inputs
+specified in the @code{#:cargo-inputs} and @code{#:cargo-development-inputs}
+parameters available to cargo. The @code{install} phase installs any crate the
+binaries if they are defined by the crate.
 @end defvr
 
 @cindex Clojure (programming language)
-- 
2.21.0


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From ee47fe46390f7996e77a8af7974899be68000dda Mon Sep 17 00:00:00 2001
From: Ivan Petkov <ivanppetkov@gmail.com>
Date: Fri, 17 May 2019 00:26:07 -0700
Subject: [PATCH 5/7] import: crate: define dependencies as arguments

* guix/import/crate.scm:
(crate-fetch)[input-crates]: Rename to dev-crates.
[native-input-crates]: Rename to dev-dep-crates.
[inputs]: Rename to cargo-inputs.
[native-inputs]: Rename to cargo-development-inputs.
(maybe-cargo-inputs): Add it.
(maybe-cargo-development-inputs): Add it.
(maybe-arguments): Add it.
(make-crate-sexp): Use new procedures.
[inputs]: Rename to cargo-inputs.
[native-inputs]: Rename to cargo-development-inputs.
* guix/import/utils.scm: (package-names->package-inputs): Make public.
Add doc string.
---
 guix/import/crate.scm | 47 +++++++++++++++++++++++++++++++++----------
 guix/import/utils.scm |  4 ++++
 2 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/guix/import/crate.scm b/guix/import/crate.scm
index e0b400d054..9a73d9fe16 100644
--- a/guix/import/crate.scm
+++ b/guix/import/crate.scm
@@ -65,29 +65,53 @@
              (path (string-append "/" version "/dependencies"))
              (deps-json (json-fetch-alist (string-append crate-url name path)))
              (deps (assoc-ref deps-json "dependencies"))
-             (input-crates (filter (crate-kind-predicate "normal") deps))
-             (native-input-crates
+             (dep-crates (filter (crate-kind-predicate "normal") deps))
+             (dev-dep-crates
               (filter (lambda (dep)
                         (not ((crate-kind-predicate "normal") dep))) deps))
-             (inputs (crates->inputs input-crates))
-             (native-inputs (crates->inputs native-input-crates))
+             (cargo-inputs (crates->inputs dep-crates))
+             (cargo-development-inputs (crates->inputs dev-dep-crates))
              (home-page (match homepage
                           (() repository)
                           (_ homepage))))
     (callback #:name name #:version version
-              #:inputs inputs #:native-inputs native-inputs
+              #:cargo-inputs cargo-inputs
+              #:cargo-development-inputs cargo-development-inputs
               #:home-page home-page #:synopsis synopsis
               #:description description #:license license)))
 
-(define* (make-crate-sexp #:key name version inputs native-inputs
+(define (maybe-cargo-inputs package-names)
+  (match (package-names->package-inputs package-names)
+    (()
+     '())
+    ((package-inputs ...)
+     `((#:cargo-inputs ,package-inputs)))))
+
+(define (maybe-cargo-development-inputs package-names)
+  (match (package-names->package-inputs package-names)
+    (()
+     '())
+    ((package-inputs ...)
+     `((#:cargo-development-inputs ,package-inputs)))))
+
+(define (maybe-arguments arguments)
+  (match arguments
+    (()
+     '())
+    ((args ...)
+     `((arguments (,'quasiquote ,args))))))
+
+(define* (make-crate-sexp #:key name version cargo-inputs cargo-development-inputs
                           home-page synopsis description license
                           #:allow-other-keys)
   "Return the `package' s-expression for a rust package with the given NAME,
-VERSION, INPUTS, NATIVE-INPUTS, HOME-PAGE, SYNOPSIS, DESCRIPTION, and LICENSE."
+VERSION, CARGO-INPUTS, CARGO-DEVELOPMENT-INPUTS, HOME-PAGE, SYNOPSIS, DESCRIPTION,
+and LICENSE."
   (let* ((port (http-fetch (crate-uri name version)))
          (guix-name (crate-name->package-name name))
-         (inputs (map crate-name->package-name inputs))
-         (native-inputs (map crate-name->package-name native-inputs))
+         (cargo-inputs (map crate-name->package-name cargo-inputs))
+         (cargo-development-inputs (map crate-name->package-name
+                                        cargo-development-inputs))
          (pkg `(package
                    (name ,guix-name)
                    (version ,version)
@@ -99,8 +123,9 @@ VERSION, INPUTS, NATIVE-INPUTS, HOME-PAGE, SYNOPSIS, DESCRIPTION, and LICENSE."
                               (base32
                                ,(bytevector->nix-base32-string (port-sha256 port))))))
                    (build-system cargo-build-system)
-                   ,@(maybe-native-inputs native-inputs "src")
-                   ,@(maybe-inputs inputs "src")
+                   ,@(maybe-arguments (append (maybe-cargo-inputs cargo-inputs)
+                                              (maybe-cargo-development-inputs
+                                                cargo-development-inputs)))
                    (home-page ,(match home-page
                                  (() "")
                                  (_ home-page)))
diff --git a/guix/import/utils.scm b/guix/import/utils.scm
index 63fc9bbb27..84503ab907 100644
--- a/guix/import/utils.scm
+++ b/guix/import/utils.scm
@@ -52,6 +52,7 @@
             url-fetch
             guix-hash-url
 
+            package-names->package-inputs
             maybe-inputs
             maybe-native-inputs
             package->definition
@@ -236,6 +237,9 @@ into a proper sentence and by using two spaces between sentences."
                               cleaned 'pre ".  " 'post)))
 
 (define* (package-names->package-inputs names #:optional (output #f))
+  "Given a list of PACKAGE-NAMES, and an optional OUTPUT, tries to generate a
+quoted list of inputs, as suitable to use in an 'inputs' field of a package
+definition."
   (map (lambda (input)
          (cons* input (list 'unquote (string->symbol input))
                             (or (and output (list output))
-- 
2.21.0


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From d6ee18d7df3af4b2a6ca445328c3c88cf145ffd5 Mon Sep 17 00:00:00 2001
From: Ivan Petkov <ivanppetkov@gmail.com>
Date: Tue, 16 Apr 2019 03:40:14 -0700
Subject: [PATCH 6/7] gnu: crate: add unicode-xid

gnu/local.mk: (GNU_SYSTEM_MODULES): Add new file.
gnu/packages/crates-io.scm: (rust-unicode-xid): New variable.
---
 gnu/local.mk               |  1 +
 gnu/packages/crates-io.scm | 45 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 gnu/packages/crates-io.scm

diff --git a/gnu/local.mk b/gnu/local.mk
index 907641ff3e..048359ce4e 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -121,6 +121,7 @@ GNU_SYSTEM_MODULES =				\
   %D%/packages/cpp.scm 				\
   %D%/packages/cppi.scm				\
   %D%/packages/cran.scm				\
+  %D%/packages/crates-io.scm			\
   %D%/packages/cross-base.scm			\
   %D%/packages/crypto.scm			\
   %D%/packages/cryptsetup.scm			\
diff --git a/gnu/packages/crates-io.scm b/gnu/packages/crates-io.scm
new file mode 100644
index 0000000000..533fe0d21e
--- /dev/null
+++ b/gnu/packages/crates-io.scm
@@ -0,0 +1,45 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2019 Ivan Petkov <ivanppetkov@gmail.com>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu packages crates-io)
+  #:use-module (guix build-system cargo)
+  #:use-module (guix download)
+  #:use-module ((guix licenses) #:prefix license:)
+  #:use-module (guix packages))
+
+(define-public rust-unicode-xid
+  (package
+    (name "rust-unicode-xid")
+    (version "0.1.0")
+    (source
+      (origin
+        (method url-fetch)
+        (uri (crate-uri "unicode-xid" version))
+        (file-name
+          (string-append name "-" version ".tar.gz"))
+        (sha256
+          (base32
+            "1z57lqh4s18rr4x0j4fw4fmp9hf9346h0kmdgqsqx0fhjr3k0wpw"))))
+    (build-system cargo-build-system)
+    (home-page
+      "https://github.com/unicode-rs/unicode-xid")
+    (synopsis "Determine Unicode XID related properties")
+    (description "Determine whether characters have the XID_Start
+or XID_Continue properties according to Unicode Standard Annex #31.")
+    ;; Dual licensed.
+    (license (list license:asl2.0 license:expat))))
-- 
2.21.0


[-- Attachment #8: 0007-gnu-crate-Add-proc-macro2-and-quote.patch --]
[-- Type: application/octet-stream, Size: 2562 bytes --]

From 4caa240fd6a245b89e640f6ef1fcaaf9a2b06c3e Mon Sep 17 00:00:00 2001
From: Ivan Petkov <ivanppetkov@gmail.com>
Date: Tue, 16 Apr 2019 03:42:27 -0700
Subject: [PATCH 7/7] gnu: crate: Add proc-macro2 and quote

* gnu/packages/crates-io.scm: (rust-proc-macro2): New variable.
(rust-quote): New variable.
---
 gnu/packages/crates-io.scm | 47 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/gnu/packages/crates-io.scm b/gnu/packages/crates-io.scm
index 533fe0d21e..b480b6fe56 100644
--- a/gnu/packages/crates-io.scm
+++ b/gnu/packages/crates-io.scm
@@ -43,3 +43,50 @@
 or XID_Continue properties according to Unicode Standard Annex #31.")
     ;; Dual licensed.
     (license (list license:asl2.0 license:expat))))
+
+(define-public rust-proc-macro2
+  (package
+    (name "rust-proc-macro2")
+    (version "0.4.27")
+    (source
+      (origin
+        (method url-fetch)
+        (uri (crate-uri "proc-macro2" version))
+        (file-name
+          (string-append name "-" version ".tar.gz"))
+        (sha256
+          (base32
+            "05c92v787snyaq4ss16vxc9mdv6zndfgsdq8k3hnnyffmsf7ycad"))))
+    (build-system cargo-build-system)
+    (arguments
+      `(#:cargo-inputs (("rust-unicode-xid" ,rust-unicode-xid))
+        #:cargo-development-inputs (("rust-quote" ,rust-quote))))
+    (home-page "https://github.com/alexcrichton/proc-macro2")
+    (synopsis "Stable implementation of the upcoming new `proc_macro` API")
+    (description "This package provides a stable implementation of the upcoming new
+`proc_macro` API.  Comes with an option, off by default, to also reimplement itself
+in terms of the upstream unstable API.")
+    ;; Dual licensed.
+    (license (list license:asl2.0 license:expat))))
+
+(define-public rust-quote
+  (package
+    (name "rust-quote")
+    (version "0.6.12")
+    (source
+      (origin
+        (method url-fetch)
+        (uri (crate-uri "quote" version))
+        (file-name
+          (string-append name "-" version ".tar.gz"))
+        (sha256
+          (base32
+            "1nw0klza45hf127kfyrpxsxd5jw2l6h21qxalil3hkr7bnf7kx7s"))))
+    (build-system cargo-build-system)
+    (arguments
+      `(#:cargo-inputs (("rust-proc-macro2" ,rust-proc-macro2))))
+    (home-page "https://github.com/dtolnay/quote")
+    (synopsis "Quasi-quoting macro quote!(...)")
+    (description "Quasi-quoting macro quote!(...)")
+    ;; Dual licensed.
+    (license (list license:asl2.0 license:expat))))
-- 
2.21.0