re-think packages and directories in cluster_codegen.sh

kcp uses an entirely different concept of placing the packages. Whereas the examples in this repo
follow a

/ <singlecluster>          <-- all single-cluster code
/ <base outputdir>
+-- clientset/versioned/   <-- cluster-aware clientset
+-- informers/
+-- listers/

structure, but in kcp it's

/ <singlecluster>
+-- clientset/
|   +-- versioned/     <-- single-cluster clientset
|        +-- cluster/  <-- cluster-ware clientset
+-- listers
+-- informers

Placing the cluster clientset right into the singlecluster clientset, but keeping the listers and
informers standalone (since there are no single-cluster listers and informers in the kcp SDK).

Making both structures possible would either require a bunch of magic, or some explicit, IMHO easier
to understand CLI flags to control exactly what you want to have happen. I have sacrified to a degree
the concept of "naming" a clientset and the "versioned" subdirectory, also because in kcp the
cluster-aware clientset doesn't itself contain a clientset/versioned/ subdirectory.

On-behalf-of: @SAP christoph.mewes@sap.com

Author: xrstf

cluster_codegen.sh

@@ -61,23 +61,42 @@ function cluster::codegen::internal::grep() {
 #     client.  If this is not set, clients for all APIs under the input-dir
 #     will be generated (under the --output-pkg).
 #
+#   --boilerplate <string = path_to_kube_codegen_boilerplate>
+#     An optional override for the header file to insert into generated files.
+#
 #   --output-dir <string>
 #     The root directory under which to emit code.  Each aspect of client
-#     generation will make one or more subdirectories.
+#     generation will make one or more subdirectories unless an explicit
+#     directory for that aspect is configured also.
 #
 #   --output-pkg <string>
 #     The Go package path (import path) of the --output-dir.  Each aspect of
-#     client generation will make one or more sub-packages.
+#     client generation will make one or more sub-packages unless an explicit
+#     package for that aspect is configured also.
 #
-#   --boilerplate <string = path_to_kube_codegen_boilerplate>
-#     An optional override for the header file to insert into generated files.
+#   --versioned-clientset-dir <string>
+#     The root directory under which to emit the generated cluster-aware clientset.
+#     Overwrites the automatic detection based on --output-dir.
 #
-#   --clientset-name <string = "clientset">
-#     An optional override for the leaf name of the generated "clientset" directory.
+#   --versioned-clientset-pkg <string>
+#     The Go package path (import path) of the --versioned-clientset-dir.
+#     Overwrites the automatic detection based on --output-dir.
 #
-#   --versioned-name <string = "versioned">
-#     An optional override for the leaf name of the generated
-#     "<clientset>/versioned" directory.
+#   --informers-dir <string>
+#     The root directory under which to emit the generated cluster-aware informers.
+#     Overwrites the automatic detection based on --output-dir.
+#
+#   --informers-pkg <string>
+#     The Go package path (import path) of the --informers-dir.
+#     Overwrites the automatic detection based on --output-dir.
+#
+#   --listers-dir <string>
+#     The root directory under which to emit the generated cluster-aware listers.
+#     Overwrites the automatic detection based on --output-dir.
+#
+#   --listers-pkg <string>
+#     The Go package path (import path) of the --listers-dir.
+#     Overwrites the automatic detection based on --output-dir.
 #
 #   --single-cluster-versioned-clientset-pkg
 #     The package name of the generated versioned Kubernetes clientset, e.g.
@@ -89,55 +108,54 @@ function cluster::codegen::internal::grep() {
 #     "acme.corp/sdk/generated/applyconfigurations". This has to have already been
 #     generated by k8s.io/code-generator.
 #
-#   --single-cluster-listers-pkg
-#     The optional name of the generated Kubernetes listers package, e.g.
-#     "acme.corp/sdk/generated/listers". This has to have already been
-#     generated by k8s.io/code-generator. If not specified, the generated cluster
-#     listers will include the necessary interfaces themselves.
-#
 #   --single-cluster-informers-pkg
 #     The optional name of the generated Kubernetes informers package, e.g.
 #     "acme.corp/sdk/generated/informers". This has to have already been
 #     generated by k8s.io/code-generator. If not specified, the generated cluster
 #     informers will include the necessary interfaces themselves.
 #
+#   --single-cluster-listers-pkg
+#     The optional name of the generated Kubernetes listers package, e.g.
+#     "acme.corp/sdk/generated/listers". This has to have already been
+#     generated by k8s.io/code-generator. If not specified, the generated cluster
+#     listers will include the necessary interfaces themselves.
+#
 #   --with-watch
 #     Enables generation of listers and informers for APIs which support WATCH.
 #
-#   --listers-name <string = "listers">
-#     An optional override for the leaf name of the generated "listers" directory.
-#
-#   --informers-name <string = "informers">
-#     An optional override for the leaf name of the generated "informers" directory.
-#
 #   --plural-exceptions <string = "">
 #     An optional list of comma separated plural exception definitions in Type:PluralizedType form.
 #
 function cluster::codegen::gen_client() {
     local in_dir=""
     local one_input_api=""
+    local boilerplate="${CLUSTER_CODEGEN_ROOT}/hack/boilerplate.go.txt"
     local out_dir=""
     local out_pkg=""
-    local clientset_subdir="clientset"
-    local clientset_versioned_name="versioned"
-    local watchable="false"
-    local listers_subdir="listers"
-    local informers_subdir="informers"
-    local boilerplate="${CLUSTER_CODEGEN_ROOT}/hack/boilerplate.go.txt"
-    local plural_exceptions=""
-    local v="${KUBE_VERBOSE:-0}"
-    local prefers_protobuf="false"
+    local versioned_clientset_dir=""
+    local versioned_clientset_pkg=""
+    local informers_dir=""
+    local informers_pkg=""
+    local listers_dir=""
+    local listers_pkg=""
     local single_cluster_versioned_clientset_pkg=""
     local single_cluster_applyconfigurations_pkg=""
-    local single_cluster_listers_pkg=""
     local single_cluster_informers_pkg=""
+    local single_cluster_listers_pkg=""
+    local watchable="false"
+    local plural_exceptions=""
+    local v="${KUBE_VERBOSE:-0}"
 
     while [ "$#" -gt 0 ]; do
         case "$1" in
             "--one-input-api")
                 one_input_api="/$2"
                 shift 2
                 ;;
+            "--boilerplate")
+                boilerplate="$2"
+                shift 2
+                ;;
             "--output-dir")
                 out_dir="$2"
                 shift 2
@@ -146,28 +164,28 @@ function cluster::codegen::gen_client() {
                 out_pkg="$2"
                 shift 2
                 ;;
-            "--boilerplate")
-                boilerplate="$2"
+            "--versioned-clientset-dir")
+                versioned_clientset_dir="$2"
                 shift 2
                 ;;
-            "--clientset-name")
-                clientset_subdir="$2"
+            "--versioned-clientset-pkg")
+                versioned_clientset_pkg="$2"
                 shift 2
                 ;;
-            "--versioned-name")
-                clientset_versioned_name="$2"
+            "--informers-dir")
+                informers_dir="$2"
                 shift 2
                 ;;
-            "--with-watch")
-                watchable="true"
-                shift
+            "--informers-pkg")
+                informers_pkg="$2"
+                shift 2
                 ;;
-            "--listers-name")
-                listers_subdir="$2"
+            "--listers-dir")
+                listers_dir="$2"
                 shift 2
                 ;;
-            "--informers-name")
-                informers_subdir="$2"
+            "--listers-pkg")
+                listers_pkg="$2"
                 shift 2
                 ;;
             "--single-cluster-versioned-clientset-pkg")
@@ -178,13 +196,17 @@ function cluster::codegen::gen_client() {
                 single_cluster_applyconfigurations_pkg="$2"
                 shift 2
                 ;;
+            "--single-cluster-informers-pkg")
+                single_cluster_informers_pkg="$2"
+                shift 2
+                ;;
             "--single-cluster-listers-pkg")
                 single_cluster_listers_pkg="$2"
                 shift 2
                 ;;
-            "--single-cluster-informers-pkg")
-                single_cluster_informers_pkg="$2"
-                shift 2
+            "--with-watch")
+                watchable="true"
+                shift
                 ;;
             "--plural-exceptions")
                 plural_exceptions="$2"
@@ -209,14 +231,6 @@ function cluster::codegen::gen_client() {
         echo "input-dir argument is required" >&2
         return 1
     fi
-    if [ -z "${out_dir}" ]; then
-        echo "--output-dir is required" >&2
-        return 1
-    fi
-    if [ -z "${out_pkg}" ]; then
-        echo "--output-pkg is required" >&2
-        return 1
-    fi
     if [ -z "${single_cluster_versioned_clientset_pkg}" ]; then
         echo "--single-cluster-versioned-clientset-pkg is required" >&2
         return 1
@@ -226,8 +240,6 @@ function cluster::codegen::gen_client() {
         return 1
     fi
 
-    mkdir -p "${out_dir}"
-
     (
         # To support running this from anywhere, first cd into this directory,
         # and then install with forced module mode on and fully qualified name.
@@ -271,9 +283,25 @@ function cluster::codegen::gen_client() {
 
     echo "Generating cluster client code for ${#group_versions[@]} targets"
 
+    if [[ -z "${versioned_clientset_dir}" ]]; then
+        if [ -z "${out_dir}" ]; then
+            echo "--output-dir is required when no --versioned-clientset-dir is provided" >&2
+            return 1
+        fi
+        versioned_clientset_dir="${out_dir}/clientset/versioned"
+    fi
+
+    if [[ -z "${versioned_clientset_pkg}" ]]; then
+        if [ -z "${out_pkg}" ]; then
+            echo "--output-pkg is required when no --versioned-clientset-pkg is provided" >&2
+            return 1
+        fi
+        versioned_clientset_pkg="${out_pkg}/clientset/versioned"
+    fi
+
     ( cluster::codegen::internal::grep -l --null \
         -e '^// Code generated by cluster-client-gen. DO NOT EDIT.$' \
-        -r "${out_dir}/${clientset_subdir}" \
+        -r "${versioned_clientset_dir}" \
         --include '*.go' \
         || true \
     ) | xargs -0 rm -f
@@ -285,9 +313,8 @@ function cluster::codegen::gen_client() {
     "${gobin}/cluster-client-gen" \
         -v "${v}" \
         --go-header-file "${boilerplate}" \
-        --output-dir "${out_dir}/${clientset_subdir}" \
-        --output-pkg "${out_pkg}/${clientset_subdir}" \
-        --clientset-name "${clientset_versioned_name}" \
+        --output-dir "${versioned_clientset_dir}" \
+        --output-pkg "${versioned_clientset_pkg}" \
         --input-base "$(cd "${in_dir}" && pwd -P)" `# must be absolute path or Go import path"` \
         --single-cluster-versioned-clientset-pkg "${single_cluster_versioned_clientset_pkg}" \
         --single-cluster-applyconfigurations-pkg "${single_cluster_applyconfigurations_pkg}" \
@@ -297,38 +324,70 @@ function cluster::codegen::gen_client() {
     if [ "${watchable}" == "true" ]; then
         echo "Generating cluster lister code for ${#input_pkgs[@]} targets"
 
+        if [[ -z "${listers_dir}" ]]; then
+            if [ -z "${out_dir}" ]; then
+                echo "--output-dir is required when no --listers-dir is provided" >&2
+                return 1
+            fi
+            listers_dir="${out_dir}/listers"
+        fi
+
+        if [[ -z "${listers_pkg}" ]]; then
+            if [ -z "${out_pkg}" ]; then
+                echo "--output-pkg is required when no --listers-pkg is provided" >&2
+                return 1
+            fi
+            listers_pkg="${out_pkg}/listers"
+        fi
+
         ( cluster::codegen::internal::grep -l --null \
             -e '^// Code generated by cluster-lister-gen. DO NOT EDIT.$' \
-            -r "${out_dir}/${listers_subdir}" \
+            -r "${listers_dir}" \
             --include '*.go' \
             || true \
         ) | xargs -0 rm -f
 
         "${gobin}/cluster-lister-gen" \
             -v "${v}" \
             --go-header-file "${boilerplate}" \
-            --output-dir "${out_dir}/${listers_subdir}" \
-            --output-pkg "${out_pkg}/${listers_subdir}" \
+            --output-dir "${listers_dir}" \
+            --output-pkg "${listers_pkg}" \
             --single-cluster-listers-pkg "${single_cluster_listers_pkg}" \
             --plural-exceptions "${plural_exceptions}" \
             "${input_pkgs[@]}"
 
         echo "Generating cluster informer code for ${#input_pkgs[@]} targets"
 
+        if [[ -z "${informers_dir}" ]]; then
+            if [ -z "${out_dir}" ]; then
+                echo "--output-dir is required when no --informers-dir is provided" >&2
+                return 1
+            fi
+            informers_dir="${out_dir}/informers"
+        fi
+
+        if [[ -z "${informers_pkg}" ]]; then
+            if [ -z "${out_pkg}" ]; then
+                echo "--output-pkg is required when no --informers-pkg is provided" >&2
+                return 1
+            fi
+            informers_pkg="${out_pkg}/informers"
+        fi
+
         ( cluster::codegen::internal::grep -l --null \
             -e '^// Code generated by cluster-informer-gen. DO NOT EDIT.$' \
-            -r "${out_dir}/${informers_subdir}" \
+            -r "${informers_dir}" \
             --include '*.go' \
             || true \
         ) | xargs -0 rm -f
 
         "${gobin}/cluster-informer-gen" \
             -v "${v}" \
             --go-header-file "${boilerplate}" \
-            --output-dir "${out_dir}/${informers_subdir}" \
-            --output-pkg "${out_pkg}/${informers_subdir}" \
-            --versioned-clientset-pkg "${out_pkg}/${clientset_subdir}/${clientset_versioned_name}" \
-            --listers-pkg "${out_pkg}/${listers_subdir}" \
+            --output-dir "${informers_dir}" \
+            --output-pkg "${informers_pkg}" \
+            --versioned-clientset-pkg "${versioned_clientset_pkg}" \
+            --listers-pkg "${listers_pkg}" \
             --single-cluster-listers-pkg "${single_cluster_listers_pkg}" \
             --single-cluster-informers-pkg "${single_cluster_informers_pkg}" \
             --single-cluster-versioned-clientset-pkg "${single_cluster_versioned_clientset_pkg}" \