stack/nodejs: add yarn

Instead of having softwares install yarn, unify this in nodejs stack.

Yarn usage is similar to nodejs usage, if a specific version is needed,
software should use macro to expose which yarn version to use, example:

    [yarn]
    <= yarn-1.17.3

Then sections can use yarn by having ${yarn:location}/bin/ in their path.

yarn will use the default [nodejs], so to another nodejs version, the same
pattern can be used:

    [nodejs]
    <= nodejs-10.6.0

component/yarn/buildout.cfg

+# https://classic.yarnpkg.com/ package manager for nodejs
+
+[buildout]
+extends =
+  ../nodejs/buildout.cfg
+
+[yarn]
+<= yarn-1.22.10
+
+[yarn-1.22.10]
+<= yarn-wrapper
+yarn-download = ${yarn-download-1.22.10:location}
+
+[yarn-1.17.3]
+<= yarn-wrapper
+yarn-download = ${yarn-download-1.17.3:location}
+
+[yarn-1.16.0]
+<= yarn-wrapper
+yarn-download = ${yarn-download-1.16.0:location}
+
+[yarn-1.3.2]
+<= yarn-wrapper
+yarn-download = ${yarn-download-1.3.2:location}
+
+[yarn-wrapper]
+recipe = slapos.recipe.template:jinja2
+rendered = ${:location}/bin/yarn
+template = inline:
+  #!/bin/sh
+  PATH=${nodejs:location}/bin/:$PATH
+  exec ${:yarn-download}/bin/yarn $@
+location = ${buildout:parts-directory}/${:_buildout_section_name_}
+bin-yarn = ${:rendered}
+
+[yarn-download]
+recipe = slapos.recipe.build:download-unpacked
+url = https://github.com/yarnpkg/yarn/releases/download/v${:version}/yarn-v${:version}.tar.gz
+
+[yarn-download-1.22.10]
+<= yarn-download
+version = 1.22.10
+md5sum = 52e8dbe9d0cb90683dd3ee2ebf2becb8
+
+[yarn-download-1.17.3]
+<= yarn-download
+version = 1.17.3
+md5sum = 4a02e1687a150113ad6b0215f9afdb3e
+
+[yarn-download-1.3.2]
+<= yarn-download
+version = 1.3.2
+md5sum = db82fa09c996e9318f2f1d2ab99228f9
+
+[yarn-download-1.16.0]
+<= yarn-download
+version = 1.16.0
+md5sum = 46790033c23803387890f545e4040690

software/gitlab/software.cfg

@@ -3,6 +3,7 @@
 extends =
     buildout.hash.cfg
     ../../stack/slapos.cfg
+    ../../stack/nodejs.cfg
     ../../stack/monitor/buildout.cfg
     ../../component/ruby/buildout.cfg
     ../../component/golang/buildout.cfg
@@ -11,7 +12,6 @@ extends =
     ../../component/cmake/buildout.cfg
     ../../component/icu/buildout.cfg
     ../../component/pkgconfig/buildout.cfg
-    ../../component/nodejs/buildout.cfg
     ../../component/openssl/buildout.cfg
     ../../component/nginx/buildout.cfg
     ../../component/xz-utils/buildout.cfg
@@ -67,12 +67,11 @@ parts =
 [slapos.cookbook-repository]
 revision = 571d6514f7290e8faa9439c4b86aa2f6c87df261
 
-
+[nodejs]
+<= nodejs-8.12.0
 [yarn]
-# need this version of Yarn
-recipe = slapos.recipe.build:download-unpacked
-url = https://github.com/yarnpkg/yarn/releases/download/v1.3.2/yarn-v1.3.2.tar.gz
-md5sum = db82fa09c996e9318f2f1d2ab99228f9
+<= yarn-1.3.2
+
 
 ############################
 #   Software compilation   #
@@ -122,7 +121,7 @@ bundle1.17.3 = ${buildout:parts-directory}/${:_buildout_section_name_}/lib/ruby/
 # (python-4gitlab puts interpreter into ${buildout:bin-directory})
 environment =
 
-  PATH    = ${yarn:location}/bin:${:ruby-location}/bin:${cmake:location}/bin:${pkgconfig:location}/bin:${nodejs-8.12.0:location}/bin:${postgresql10:location}/bin:${redis28:location}/bin:${git:location}/bin:${buildout:bin-directory}:%(PATH)s
+  PATH    = ${yarn:location}/bin:${:ruby-location}/bin:${cmake:location}/bin:${pkgconfig:location}/bin:${nodejs:location}/bin:${postgresql10:location}/bin:${redis28:location}/bin:${git:location}/bin:${buildout:bin-directory}:%(PATH)s
 
 
 # gitlab, gitlab-shell & gitlab-workhorse checked out as git repositories
@@ -210,7 +209,7 @@ make-binary =
 make-targets= cd ${:path} && npm install
 
 environment =
-  PATH=${nodejs-8.12.0:location}/bin/:%(PATH)s
+  PATH=${nodejs:location}/bin/:%(PATH)s
 
 #our go infrastructure not currently supporting submodules, IIRC
 # https://lab.nexedi.com/nexedi/slapos/merge_requests/337

software/grafana/software.cfg

@@ -27,12 +27,7 @@ parts =
 <= nodejs-10.6.0
 
 [yarn]
-# this could become a component, but it needs to be invoked from nodejs explicitly,
-# otherwise it uses system's nodejs
-recipe = slapos.recipe.build:download-unpacked
-url = https://github.com/yarnpkg/yarn/releases/download/v1.16.0/yarn-v1.16.0.tar.gz
-md5sum = 46790033c23803387890f545e4040690
-
+<= yarn-1.16.0
 
 [gowork]
 # All the softwares installed in the go workspace have "non standard" installation

software/theia/software.cfg

 [buildout]
 extends =
-   ../../component/nodejs/buildout.cfg
    ../../component/caddy/buildout.cfg
    ../../component/git/buildout.cfg
    ../../component/bash/buildout.cfg
@@ -13,6 +12,7 @@ extends =
    ../../component/coreutils/buildout.cfg
    ../../component/java-jdk/buildout.cfg
    ../../component/fonts/buildout.cfg
+   ../../stack/nodejs.cfg
    ../../stack/slapos.cfg
    ../../stack/monitor/buildout.cfg
    ../../component/defaults.cfg
@@ -37,13 +37,7 @@ max_version = 0
 <= nodejs-12.18.3
 
 [yarn]
-# this could become a component, but it needs to be invoked from nodejs explicitly,
-# otherwise it uses system's nodejs
-# XXX why don't we build a wrapper ?
-version = 1.17.3
-recipe = slapos.recipe.build:download-unpacked
-url = https://github.com/yarnpkg/yarn/releases/download/v${:version}/yarn-v${:version}.tar.gz
-md5sum = 4a02e1687a150113ad6b0215f9afdb3e
+<= yarn-1.17.3
 
 [slapos-standalone]
 recipe = zc.recipe.egg

stack/nodejs.cfg

 [buildout]
 extends =
   ../component/nodejs/buildout.cfg
+  ../component/yarn/buildout.cfg
   ../stack/slapos.cfg
 
 parts =