oe-setup-build: add a tool for discovering config templates and setting up builds

This is another piece of the puzzle in setting up builds from nothing
without having to write custom scripts or use external tools.

After layers have been fetched and placed into their respective locations by
oe-setup-layers, one would surely want to proceed to the actual build, and here's how:

1. Without arguments the tool reads available layers
from .oe-layers.json file (written out by oe-setup-layers or a fallback under scripts/),
prints what templates it has found, and asks the user to select one, as seen below.
This will land the user in a shell ready to run bitbake:

=============================================
alex@Zen2:/srv/work/alex$ ./setup-build
Available build configurations:

1. alex-configuration-gadget
This configuration will set up a build for the purposes of supporting gadget.

2. alex-configuration-gizmo
This configuration allows building a gizmo.

3. poky-default
This is the default build configuration for the Poky reference distribution.

Re-run with 'list -v' to see additional information.
Please choose a configuration by its number: 1
Running: TEMPLATECONF=/srv/work/alex/meta-alex/conf/templates/configuration-gadget . /srv/work/alex/poky/oe-init-build-env /srv/work/alex/build-alex-configuration-gadget && /bin/bash
You had no conf/local.conf file. This configuration file has therefore been
created for you from /srv/work/alex/meta-alex/conf/templates/configuration-gadget/local.conf.sample
You may wish to edit it to, for example, select a different MACHINE (target
hardware).

You had no conf/bblayers.conf file. This configuration file has therefore been
created for you from /srv/work/alex/meta-alex/conf/templates/configuration-gadget/bblayers.conf.sample
To add additional metadata layers into your configuration please add entries
to conf/bblayers.conf.

The Yocto Project has extensive documentation about OE including a reference
manual which can be found at:
    https://docs.yoctoproject.org

For more information about OpenEmbedded see the website:
    https://www.openembedded.org/

This configuration will set up a build for the purposes of supporting gadget.
Please refer to meta-alex/README for additional details and available bitbake targets.
==============================================

2. It is also possible to list available configurations without selecting one using
'setup-build list' or to select and setup one non-interactively with 'setup-build setup'.

3. The full set of command line options is:

$ ./setup-build --help
usage: setup-build [-h] [--layerlist LAYERLIST] {list,setup} ...

A script that discovers available build configurations and sets up a build environment based on one of them. Run without arguments to choose one interactively.

positional arguments:
  {list,setup}
    list                List available configurations
    setup               Set up a build environment and open a shell session with it, ready to run builds.

optional arguments:
  -h, --help            show this help message and exit
  --layerlist LAYERLIST
                        Where to look for available layers (as written out by setup-layers script) (default is /srv/work/alex/.oe-layers.json).

$ ./setup-build list --help
usage: setup-build list [-h] [-v]

optional arguments:
  -h, --help  show this help message and exit
  -v          Print detailed information and usage notes for each available build configuration.

$ ./setup-build setup --help
usage: setup-build setup [-h] [-c configuration_name] [-b build_path] [--no-shell]

optional arguments:
  -h, --help            show this help message and exit
  -c configuration_name
                        Use a build configuration configuration_name to set up a build environment (run this script with 'list' to see what is available)
  -b build_path         Set up a build directory in build_path (run this script with 'list -v' to see where it would be by default)
  --no-shell            Create a build directory but do not start a shell session with the build environment from it.

4. There's an an added hint in oe-setup-layers about how to proceed (as it is really not user-friendly
to fetch the layer repos successfully and then exit without a word), and a symlink to the script
from the top level layer checkout directory.

5. The selftest to check layer setup has been adjusted to run a basic check for template
discovery and build setup. The revision of poky to be cloned has been bumped to 4.1,
as that's the first version with a default template in a standard location.

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

3 files changed, 139 insertions, 0 deletions

diff --git a/scripts/.oe-layers.json b/scripts/.oe-layers.json
new file mode 100644
index 0000000000..1b00a84b54
--- /dev/null
+++ b/scripts/.oe-layers.json
@@ -0,0 +1,7 @@
+{
+    "layers": [
+        "../meta-poky",
+        "../meta"
+    ],
+    "version": "1.0"
+}
diff --git a/scripts/oe-setup-build b/scripts/oe-setup-build
new file mode 100755
index 0000000000..5364f2b481
--- /dev/null
+++ b/scripts/oe-setup-build
@@ -0,0 +1,122 @@
+#!/usr/bin/env python3
+#
+# Copyright OpenEmbedded Contributors
+#
+# SPDX-License-Identifier: MIT
+#
+
+import argparse
+import json
+import os
+import subprocess
+
+def defaultlayers():
+    return os.path.abspath(os.path.join(os.path.dirname(__file__), '.oe-layers.json'))
+
+def makebuildpath(topdir, template):
+    return os.path.join(topdir, "build-{}".format(template))
+
+def discover_templates(layers_file):
+    if not os.path.exists(layers_file):
+        print("List of layers {} does not exist; were the layers set up using the setup-layers script?".format(layers_file))
+        return None
+
+    templates = []
+    layers_list = json.load(open(layers_file))["layers"]
+    for layer in layers_list:
+        template_dir = os.path.join(os.path.dirname(layers_file), layer, 'conf','templates')
+        if os.path.exists(template_dir):
+            for d in sorted(os.listdir(template_dir)):
+                templatepath = os.path.join(template_dir,d)
+                if not os.path.isfile(os.path.join(templatepath,'local.conf.sample')):
+                    continue
+                layer_base = os.path.basename(layer)
+                templatename = "{}-{}".format(layer_base[5:] if layer_base.startswith("meta-") else layer_base, d)
+                buildpath = makebuildpath(os.getcwd(), templatename)
+                notespath = os.path.join(template_dir, d, 'conf-notes.txt')
+                try: notes = open(notespath).read()
+                except: notes = None
+                try: summary = open(os.path.join(template_dir, d, 'conf-summary.txt')).read()
+                except: summary = None
+                templates.append({"templatename":templatename,"templatepath":templatepath,"buildpath":buildpath,"notespath":notespath,"notes":notes,"summary":summary})
+
+    return templates
+
+def print_templates(templates, verbose):
+    print("Available build configurations:\n")
+
+    for i in range(len(templates)):
+        t = templates[i]
+        print("{}. {}".format(i+1, t["templatename"]))
+        print("{}".format(t["summary"].strip() if t["summary"] else "This configuration does not have a summary."))
+        if verbose:
+            print("Configuration template path:", t["templatepath"])
+            print("Build path:", t["buildpath"])
+            print("Usage notes:", t["notespath"] if t["notes"] else "This configuration does not have usage notes.")
+        print("")
+    if not verbose:
+        print("Re-run with 'list -v' to see additional information.")
+
+def list_templates(args):
+    templates = discover_templates(args.layerlist)
+    if not templates:
+        return
+
+    verbose = args.v
+    print_templates(templates, verbose)
+
+def find_template(template_name, templates):
+    print_templates(templates, False)
+    if not template_name:
+        n_s = input("Please choose a configuration by its number: ")
+        try: return templates[int(n_s) - 1]
+        except:
+            print("Invalid selection, please try again.")
+            return None
+    else:
+        for t in templates:
+            if t["templatename"] == template_name:
+                return t
+        print("Configuration {} is not one of {}, please try again.".format(tempalte_name, [t["templatename"] for t in templates]))
+        return None
+
+def setup_build_env(args):
+    templates = discover_templates(args.layerlist)
+    if not templates:
+        return
+
+    template = find_template(args.c, templates)
+    if not template:
+        return
+    builddir = args.b if args.b else template["buildpath"]
+    no_shell = args.no_shell
+    coredir = os.path.abspath(os.path.join(os.path.dirname(os.path.realpath(__file__)), '..'))
+    cmd = "TEMPLATECONF={} . {} {}".format(template["templatepath"], os.path.join(coredir, 'oe-init-build-env'), builddir)
+    if not no_shell:
+        cmd = cmd + " && {}".format(os.environ['SHELL'])
+    print("Running:", cmd)
+    subprocess.run(cmd, shell=True, executable=os.environ['SHELL'])
+
+parser = argparse.ArgumentParser(description="A script that discovers available build configurations and sets up a build environment based on one of them. Run without arguments to choose one interactively.")
+parser.add_argument("--layerlist", default=defaultlayers(), help='Where to look for available layers (as written out by setup-layers script) (default is {}).'.format(defaultlayers()))
+
+subparsers = parser.add_subparsers()
+parser_list_templates = subparsers.add_parser('list', help='List available configurations')
+parser_list_templates.add_argument('-v', action='store_true',
+        help='Print detailed information and usage notes for each available build configuration.')
+parser_list_templates.set_defaults(func=list_templates)
+
+parser_setup_env = subparsers.add_parser('setup', help='Set up a build environment and open a shell session with it, ready to run builds.')
+parser_setup_env.add_argument('-c', metavar='configuration_name', help="Use a build configuration configuration_name to set up a build environment (run this script with 'list' to see what is available)")
+parser_setup_env.add_argument('-b', metavar='build_path', help="Set up a build directory in build_path (run this script with 'list -v' to see where it would be by default)")
+parser_setup_env.add_argument('--no-shell', action='store_true',
+        help='Create a build directory but do not start a shell session with the build environment from it.')
+parser_setup_env.set_defaults(func=setup_build_env)
+
+args = parser.parse_args()
+
+if 'func' in args:
+    args.func(args)
+else:
+    from argparse import Namespace
+    setup_build_env(Namespace(layerlist=args.layerlist, c=None, b=None, no_shell=False))
diff --git a/scripts/oe-setup-layers b/scripts/oe-setup-layers
index bee4ef0fec..6fbfefd656 100755
--- a/scripts/oe-setup-layers
+++ b/scripts/oe-setup-layers
@@ -63,6 +63,7 @@ def _write_layer_list(dest, repodirs):
 def _do_checkout(args, json):
     repos = json['sources']
     repodirs = []
+    oesetupbuild = None
     for r_name in repos:
         r_data = repos[r_name]
         repodir = os.path.abspath(os.path.join(args['destdir'], r_data['path']))
@@ -108,9 +109,18 @@ def _do_checkout(args, json):
 
             if _contains_submodules(repodir):
                 print("Repo {} contains submodules, use 'git submodule update' to ensure they are up to date".format(repodir))
+        if os.path.exists(os.path.join(repodir, 'scripts/oe-setup-build')):
+            oesetupbuild = os.path.join(repodir, 'scripts/oe-setup-build')
 
     _write_layer_list(args['destdir'], repodirs)
 
+    if oesetupbuild:
+        oesetupbuild_symlink = os.path.join(args['destdir'], 'setup-build')
+        if os.path.exists(oesetupbuild_symlink):
+            os.remove(oesetupbuild_symlink)
+        os.symlink(os.path.relpath(oesetupbuild,args['destdir']),oesetupbuild_symlink)
+        print("\nRun '{}' to list available build configuration templates and set up a build from one of them.".format(oesetupbuild_symlink))
+
 parser = argparse.ArgumentParser(description="A self contained python script that fetches all the needed layers and sets them to correct revisions using data in a json format from a separate file. The json data can be created from an active build directory with 'bitbake-layers create-layers-setup destdir' and there's a sample file and a schema in meta/files/")
 
 parser.add_argument('--force-bootstraplayer-checkout', action='store_true',