Packaging ‘clang-tools-extra’ (‘clang-tidy’, etc.)

[Ludovic Courtès]

Hello!

The patch below produces a ‘clang’ package that contains
‘clang-tools-extra’ commands¹.

The problem is the size.  Before:

--8<---------------cut here---------------start------------->8---
$ guix size /gnu/store/qxdpxbvfdxfy5dnz4haql4xlxpmb5r6b-clang-10.0.0 |tail -1
total: 995.2 MiB
$ guix size /gnu/store/qxdpxbvfdxfy5dnz4haql4xlxpmb5r6b-clang-10.0.0 |head -2
store item                                                       total    self
/gnu/store/qxdpxbvfdxfy5dnz4haql4xlxpmb5r6b-clang-10.0.0           995.2   
456.5  45.9%
--8<---------------cut here---------------end--------------->8---

After:

--8<---------------cut here---------------start------------->8---
$ guix size /gnu/store/5h3xgpg33wip2b8ccri690jp6ikbq16s-clang-10.0.0 |tail -1
total: 1525.4 MiB
$ guix size /gnu/store/5h3xgpg33wip2b8ccri690jp6ikbq16s-clang-10.0.0 |head -2
store item                                                       total    self
/gnu/store/5h3xgpg33wip2b8ccri690jp6ikbq16s-clang-10.0.0          1525.4   
986.8  64.7%
--8<---------------cut here---------------end--------------->8---

(How they manage to fill that much disk space, I wonder.)

Any idea how to best package it?

We could of course have a ‘clang-full’ package, but it seems wasteful.
We could also have a separate output for the extra commands, but it’s
inconvenient.  It would be ideal to have a ‘clang-tools-extra’ package
that depends on ‘clang’, but building them separately appears to be
impossible.

Thanks in advance!  :-)

Ludo’.

¹ https://releases.llvm.org/10.0.0/tools/clang/tools/extra/docs/index.html

diff --git a/gnu/packages/llvm.scm b/gnu/packages/llvm.scm
index d6c519bcbd..a3bcd75190 100644
--- a/gnu/packages/llvm.scm
+++ b/gnu/packages/llvm.scm
@@ -166,7 +166,11 @@ compiler.  In LLVM this library is called 
\"compiler-rt\".")
     (supported-systems (delete "mips64el-linux" %supported-systems))))
 
 (define* (clang-from-llvm llvm clang-runtime hash
-                          #:key (patches '()))
+                          #:key (patches '()) tools-extra)
+  "Produce Clang with dependencies on LLVM and CLANG-RUNTIME, and applying the
+given PATCHES.  When TOOLS-EXTRA is given, it must point to the
+'clang-tools-extra' tarball, which contains code for 'clang-tidy', 'pp-trace',
+'modularize', and other tools."
   (package
     (name "clang")
     (version (package-version llvm))
@@ -187,7 +191,10 @@ compiler.  In LLVM this library is called 
\"compiler-rt\".")
     (inputs
      `(("libxml2" ,libxml2)
        ("gcc-lib" ,gcc "lib")
-       ,@(package-inputs llvm)))
+       ,@(package-inputs llvm)
+       ,@(if tools-extra
+             `(("clang-tools-extra" ,tools-extra))
+             '())))
     (propagated-inputs
      `(("llvm" ,llvm)
        ("clang-runtime" ,clang-runtime)))
@@ -208,6 +215,19 @@ compiler.  In LLVM this library is called 
\"compiler-rt\".")
        #:build-type "Release"
 
        #:phases (modify-phases %standard-phases
+                  ,@(if tools-extra
+                        `((add-after 'unpack 'add-tools-extra
+                            (lambda* (#:key inputs #:allow-other-keys)
+                              (let ((extra (assoc-ref inputs
+                                                      "clang-tools-extra")))
+                                (invoke "tar" "xf" extra)
+                                (rename-file ,(string-append
+                                               "clang-tools-extra-"
+                                               (package-version llvm)
+                                               ".src")
+                                             "tools/extra")
+                                #t))))
+                        '())
                   (add-after 'unpack 'add-missing-triplets
                     (lambda _
                       ;; Clang iterates through known triplets to search for
@@ -376,7 +396,16 @@ output), and Binutils.")
 (define-public clang-10
   (clang-from-llvm llvm-10 clang-runtime-10
                    "08fbxa2a0kr3ni35ckppj0kyvlcyaywrhpqwcdrdy0z900mhcnw8"
-                   #:patches '("clang-10.0-libc-search-path.patch")))
+                   #:patches '("clang-10.0-libc-search-path.patch")
+                   #:tools-extra
+                   #f
+                   #;(origin
+                     (method url-fetch)
+                     (uri (llvm-download-uri "clang-tools-extra"
+                                             (package-version llvm-10)))
+                     (sha256
+                      (base32
+                       
"074ija5s2jsdn0k035r2dzmryjmqxdnyg4xwvaqych2bazv8rpxc")))))
 
 (define-public clang-toolchain-10
   (make-clang-toolchain clang-10))