[9/9] Prototype go-mod-update-modules class

diff --git a/meta/classes-recipe/go-mod-update-modules.bbclass b/meta/classes-recipe/go-mod-update-modules.bbclass
new file mode 100644
index 00000000000..3253f7f0a26
--- /dev/null
+++ b/meta/classes-recipe/go-mod-update-modules.bbclass
@@ -0,0 +1,130 @@ 
+addtask do_update_modules after do_configure
+do_update_modules[nostamp] = "1"
+do_update_modules[network] = "1"
+
+python do_update_modules() {
+    import subprocess, tempfile, json, re
+    from oe.license_finder import find_licenses
+
+    def unescape_path(path):
+        """Unescape capital letters using exclamation points."""
+        return re.sub(r'!([a-z])', lambda m: m.group(1).upper(), path)
+
+    def fold_uri(uri):
+        """Fold URI for sorting shorter module paths before longer."""
+        return uri.replace(';', ' ').replace('/', '!')
+
+    # TODO duplicated in recipetools
+    def tidy_licenses(value):
+        """Flat, split and sort licenses"""
+        from oe.license import flattened_licenses
+        def _choose(a, b):
+            str_a, str_b  = sorted((" & ".join(a), " & ".join(b)), key=str.casefold)
+            return ["(%s | %s)" % (str_a, str_b)]
+        if not isinstance(value, str):
+            value = " & ".join(value)
+        return sorted(list(set(flattened_licenses(value, _choose))), key=str.casefold)
+
+    bpn = d.getVar("BPN")
+    thisdir = d.getVar("THISDIR")
+
+    mod_dir = tempfile.mkdtemp(prefix='go-mod-')
+    bb.warn("using tmp mod %s" % mod_dir)
+    #d.setVar('GOMODCACHE', mod_dir)
+    env = dict(os.environ, GOMODCACHE=mod_dir)
+
+    # TODO this feels magic
+    source = d.expand("${WORKDIR}/${GO_SRCURI_DESTSUFFIX}")
+
+    # TODO is this needed in the refresh case?
+    output = subprocess.check_output(("go", "mod", "edit", "-json"), cwd=source, env=env, text=True)
+    go_mod = json.loads(output)
+
+    output = subprocess.check_output(("go", "list", "-json=Dir,Module", "-deps", f"{go_mod['Module']['Path']}/..."), cwd=source, env=env, text=True)
+
+    #
+    # Licenses
+    #
+
+    # The output of this isn't actually valid JSON, but a series of dicts.
+    # Wrap in [] and join the dicts with ,
+    # Very frustrating that the json parser in python can't repeatedly
+    # parse from a stream.
+    pkgs = json.loads('[' + output.replace('}\n{', '},\n{') + ']')
+    # Collect licenses for the dependencies.
+    licenses = set()
+    lic_files_chksum = []
+    lic_files = {}
+    for pkg in pkgs:
+        # TODO: If the package is in a subdirectory with its own license
+        # files then report those istead of the license files found in the
+        # module root directory.
+        mod = pkg.get('Module', None)
+        if not mod or mod.get('Main', False):
+            continue
+        path = os.path.relpath(mod['Dir'], mod_dir)
+        for license_name, license_file, license_md5 in find_licenses(mod['Dir'], d):
+            lic_files[os.path.join(path, license_file)] = (license_name, license_md5)
+
+    for lic_file in lic_files:
+        license_name, license_md5 = lic_files[lic_file]
+        if license_name == "Unknown":
+            bb.warn(f"Unknown license: {lic_file} {license_md5}")
+
+        licenses.add(lic_files[lic_file][0])
+        lic_files_chksum.append(
+            f'file://pkg/mod/{lic_file};md5={license_md5}')
+
+    licenses_filename = os.path.join(thisdir, f"{bpn}-licenses.inc")
+    with open(licenses_filename, "w") as f:
+        f.write(f'LICENSE += "& {" & ".join(tidy_licenses(licenses))}"\n\n')
+        f.write('LIC_FILES_CHKSUM += "\\\n')
+        for lic in sorted(lic_files_chksum, key=fold_uri):
+            f.write('    ' + lic + ' \\\n')
+        f.write('"\n')
+
+    #
+    # Sources
+    #
+
+    # Collect the module cache files downloaded by the go list command as
+    # the go list command knows best what the go list command needs and it
+    # needs more files in the module cache than the go install command as
+    # it doesn't do the dependency pruning mentioned in the Go module
+    # reference, https://go.dev/ref/mod, for go 1.17 or higher.
+    src_uris = []
+    downloaddir = os.path.join(mod_dir, 'cache', 'download')
+    for dirpath, _, filenames in os.walk(downloaddir):
+        # We want to process files under @v directories
+        path, base = os.path.split(os.path.relpath(dirpath, downloaddir))
+        if base != '@v':
+            continue
+
+        path = unescape_path(path)
+        zipver = None
+        for name in filenames:
+            ver, ext = os.path.splitext(name)
+            if ext == '.zip':
+                chksum = bb.utils.sha256_file(os.path.join(dirpath, name))
+                src_uris.append(f'gomod://{path};version={ver};sha256sum={chksum}')
+                zipver = ver
+                break
+        for name in filenames:
+            ver, ext = os.path.splitext(name)
+            if ext == '.mod' and ver != zipver:
+                chksum = bb.utils.sha256_file(os.path.join(dirpath, name))
+                src_uris.append(f'gomod://{path};version={ver};mod=1;sha256sum={chksum}')
+
+
+    go_mods_filename = os.path.join(thisdir, f"{bpn}-go-mods.inc")
+    with open(go_mods_filename, "w") as f:
+        f.write('SRC_URI += "\\\n')
+        for uri in sorted(src_uris, key=fold_uri):
+            f.write('    ' + uri + ' \\\n')
+        f.write('"\n')
+
+    subprocess.check_output(("go", "clean", "-modcache"), cwd=source, env=env, text=True)
+}
+
+# This doesn't work as we need to wipe the inc files first so we don't try looking for LICENSE files that don't yet exist
+# RECIPE_UPGRADE_EXTRA_TASKS += "do_update_modules"