build-system/cargo: Propagate crates across builds.

* guix/build-system/cargo.scm (cargo-build): Add cargo-package-flags,
install-source flags.
* guix/build/cargo-build-system.scm (unpack-rust-crates, package): New
procedures.
(install): Also install crate sources.
(%standard-phases): Add new phases.
* doc/guix.texi (Packaging-guidelines)[Rust Crates]: Adjust to changes
in the cargo-build-system.

doc/guix.texi

@@ -32,7 +32,7 @@ Copyright @copyright{} 2015, 2016, 2017, 2019, 2020, 2021 Leo Famulari@*
 Copyright @copyright{} 2015, 2016, 2017, 2018, 2019, 2020 Ricardo Wurmus@*
 Copyright @copyright{} 2016 Ben Woodcroft@*
 Copyright @copyright{} 2016, 2017, 2018 Chris Marusich@*
-Copyright @copyright{} 2016, 2017, 2018, 2019, 2020 Efraim Flashner@*
+Copyright @copyright{} 2016, 2017, 2018, 2019, 2020, 2021 Efraim Flashner@*
 Copyright @copyright{} 2016 John Darrington@*
 Copyright @copyright{} 2016, 2017 Nikita Gillmann@*
 Copyright @copyright{} 2016, 2017, 2018, 2019, 2020 Jan Nieuwenhuizen@*
@@ -7449,8 +7449,10 @@ supports builds of packages using Cargo, the build tool of the
 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
+Regular cargo dependencies should be added to the package definition similarly
-@code{#:cargo-inputs} parameter as a list of name and spec pairs, where the
+to other packages; those needed only at build time to native-inputs, others to
+inputs.  If you need to add source-only crates then you should add them to 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
@@ -7461,8 +7463,11 @@ 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.  It will also remove an included
 @code{Cargo.lock} file to be recreated by @code{cargo} during the
-@code{build} phase.  The @code{install} phase installs the binaries
+@code{build} phase.  The @code{package} phase will run @code{cargo package}
-defined by the crate.
+to create a source crate for future use.  The @code{install} phase installs
+the binaries defined by the crate.  Unless @code{install-source? #f} is
+defined it will also install a source crate repository of itself and unpacked
+sources, to ease in future hacking on rust packages.
 @end defvr
 
 @defvr {Scheme Variable} chicken-build-system

guix/build-system/cargo.scm

@@ -5,6 +5,7 @@
 ;;; Copyright © 2016 David Craven <david@craven.ch>
 ;;; Copyright © 2019 Ivan Petkov <ivanppetkov@gmail.com>
 ;;; Copyright © 2020 Jakub Kądziołka <kuba@kadziolka.net>
+;;; Copyright © 2021 Efraim Flashner <efraim@flashner.co.il>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -77,8 +78,10 @@ to NAME and VERSION."
                       (vendor-dir "guix-vendor")
                       (cargo-build-flags ''("--release"))
                       (cargo-test-flags ''("--release"))
+                      (cargo-package-flags ''("--no-metadata" "--no-verify"))
                       (features ''())
                       (skip-build? #f)
+                      (install-source? #t)
                       (phases '(@ (guix build cargo-build-system)
                                   %standard-phases))
                       (outputs '("out"))
@@ -106,8 +109,10 @@ to NAME and VERSION."
                     #:vendor-dir ,vendor-dir
                     #:cargo-build-flags ,cargo-build-flags
                     #:cargo-test-flags ,cargo-test-flags
+                    #:cargo-package-flags ,cargo-package-flags
                     #:features ,features
                     #:skip-build? ,skip-build?
+                    #:install-source? ,install-source?
                     #:tests? ,(and tests? (not skip-build?))
                     #:phases ,phases
                     #:outputs %outputs

guix/build/cargo-build-system.scm

@@ -2,7 +2,7 @@
 ;;; Copyright © 2016 David Craven <david@craven.ch>
 ;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
 ;;; Copyright © 2019 Ivan Petkov <ivanppetkov@gmail.com>
-;;; Copyright © 2019, 2020 Efraim Flashner <efraim@flashner.co.il>
+;;; Copyright © 2019, 2020, 2021 Efraim Flashner <efraim@flashner.co.il>
 ;;; Copyright © 2020 Jakub Kądziołka <kuba@kadziolka.net>
 ;;; Copyright © 2020 Marius Bakke <marius@gnu.org>
 ;;;
@@ -73,6 +73,38 @@ Cargo.toml file present at its root."
                                             " | cut -d/ -f2"
                                             " | grep -q '^Cargo.toml$'")))))
 
+(define* (unpack-rust-crates #:key inputs vendor-dir #:allow-other-keys)
+  (define (inputs->rust-inputs inputs)
+    "Filter using the label part from INPUTS."
+    (filter (lambda (input)
+              (match input
+                ((name . _) (rust-package? name))))
+            inputs))
+  (define (inputs->directories inputs)
+    "Extract the directory part from INPUTS."
+    (match inputs
+      (((names . directories) ...)
+       directories)))
+
+  (let ((rust-inputs (inputs->directories (inputs->rust-inputs inputs))))
+    (unless (null? rust-inputs)
+      (mkdir-p "target/package")
+      (mkdir-p vendor-dir)
+      ;; TODO: copy only regular inputs to target/package, not native-inputs.
+      (for-each (lambda (input-crate)
+                  (copy-recursively (string-append input-crate
+                                                   "/share/cargo/registry")
+                                    "target/package"))
+                (delete-duplicates rust-inputs))
+
+      (for-each (lambda (crate)
+                  (invoke "tar" "xzf" crate "-C" vendor-dir))
+                (find-files "target/package" "\\.crate$"))))
+  #t)
+
+(define (rust-package? name)
+  (string-prefix? "rust-" name))
+
 (define* (configure #:key inputs
                     (vendor-dir "guix-vendor")
                     #:allow-other-keys)
@@ -170,9 +202,27 @@ directory = '" port)
       (apply invoke "cargo" "test" cargo-test-flags)
       #t))
 
-(define* (install #:key inputs outputs skip-build? features #:allow-other-keys)
+(define* (package #:key
+                  install-source?
+                  (cargo-package-flags '("--no-metadata" "--no-verify"))
+                  #:allow-other-keys)
+  "Run 'cargo-package' for a given Cargo package."
+  (if install-source?
+    (apply invoke `("cargo" "package" ,@cargo-package-flags))
+    (format #t "Not installing cargo sources, skipping `cargo package`.~%"))
+  #t)
+
+(define* (install #:key
+                  inputs
+                  outputs
+                  skip-build?
+                  install-source?
+                  features
+                  #:allow-other-keys)
   "Install a given Cargo package."
-  (let* ((out (assoc-ref outputs "out")))
+  (let* ((out      (assoc-ref outputs "out"))
+         (registry (string-append out "/share/cargo/registry"))
+         (sources  (string-append out "/share/cargo/src")))
     (mkdir-p out)
 
     ;; Make cargo reuse all the artifacts we just built instead
@@ -186,6 +236,18 @@ directory = '" port)
         (invoke "cargo" "install" "--no-track" "--path" "." "--root" out
                 "--features" (string-join features)))
 
+    (when install-source?
+      ;; Install crate tarballs and unpacked sources for later use.
+      ;; TODO: Is there a better format/directory for these files?
+      (mkdir-p sources)
+      (for-each (lambda (crate)
+                  (install-file crate registry))
+                (find-files "target/package" "\\.crate$"))
+
+      (for-each (lambda (crate)
+                  (invoke "tar" "xzf" crate "-C" sources))
+                (find-files registry "\\.crate$")))
+
     #t))
 
 (define %standard-phases
@@ -195,6 +257,8 @@ directory = '" port)
     (replace 'build build)
     (replace 'check check)
     (replace 'install install)
+    (add-after 'build 'package package)
+    (add-after 'unpack 'unpack-rust-crates unpack-rust-crates)
     (add-after 'patch-generated-file-shebangs 'patch-cargo-checksums patch-cargo-checksums)))
 
 (define* (cargo-build #:key inputs (phases %standard-phases)