Allow makefile substitutions

MODULE.bazel

@@ -9,10 +9,8 @@ module(
 bazel_dep(name = "platforms", version = "0.0.10")
 bazel_dep(name = "bazel_skylib", version = "1.7.1")
 bazel_dep(name = "rules_go", version = "0.50.1", repo_name = "io_bazel_rules_go")
+bazel_dep(name = "aspect_bazel_lib", version = "2.7.2")
 
-# This is unfortunately required by `rules_oci`.
-# https://github.com/bazel-contrib/rules_oci/issues/575
-bazel_dep(name = "aspect_bazel_lib", version = "2.7.2", dev_dependency = True)
 bazel_dep(name = "rules_oci", version = "2.0.0", dev_dependency = True)
 bazel_dep(name = "stardoc", version = "0.7.1", dev_dependency = True, repo_name = "io_bazel_stardoc")
 

helm/private/helm.bzl

@@ -73,6 +73,7 @@ def helm_chart(
         chart = chart,
         chart_json = chart_json,
         crds = crds,
+        data = data,
         deps = deps,
         images = images,
         templates = templates,

helm/private/helm_package.bzl

@@ -1,5 +1,6 @@
 """Helm rules"""
 
+load("@aspect_bazel_lib//lib:expand_make_vars.bzl", "expand_locations", "expand_variables")
 load("//helm:providers.bzl", "HelmPackageInfo")
 load("//helm/private:helm_utils.bzl", "is_stamping_enabled")
 load("//helm/private:json_to_yaml.bzl", "json_to_yaml")
@@ -108,9 +109,10 @@ def _helm_package_impl(ctx):
     args.add("-values", values_yaml)
 
     substitutions_file = ctx.actions.declare_file("{}/substitutions.json".format(ctx.label.name))
+    expanded_substitutions = {k: expand_variables(ctx, expand_locations(ctx, v, ctx.attr.data)) for k, v in ctx.attr.substitutions.items()}
     ctx.actions.write(
         output = substitutions_file,
-        content = json.encode_indent(ctx.attr.substitutions, indent = " " * 4),
+        content = json.encode_indent(expanded_substitutions, indent = " " * 4),
     )
     args.add("-substitutions", substitutions_file)
 
@@ -196,7 +198,7 @@ def _helm_package_impl(ctx):
         executable = ctx.executable._packager,
         outputs = [output, metadata_output],
         inputs = depset(
-            ctx.files.templates + ctx.files.files + ctx.files.crds + stamps + image_inputs + deps + [
+            ctx.files.templates + ctx.files.data + ctx.files.files + ctx.files.crds + stamps + image_inputs + deps + [
                 chart_yaml,
                 values_yaml,
                 templates_manifest,
@@ -240,6 +242,11 @@ helm_package = rule(
             default = [],
             allow_files = True,
         ),
+        "data": attr.label_list(
+            doc = "Additional data files used for e.g. template substitutions. Note that these files are not included in the created helm chart but only used during the build process.",
+            default = [],
+            allow_files = True,
+        ),
         "deps": attr.label_list(
             doc = "Other helm packages this package depends on.",
             providers = [HelmPackageInfo],
@@ -276,7 +283,7 @@ helm_package = rule(
             values = [1, 0, -1],
         ),
         "substitutions": attr.string_dict(
-            doc = "A dictionary of substitutions to apply to the `values.yaml` file.",
+            doc = "A dictionary of substitutions to apply to the `values.yaml` file. Supports make variable expansion. You can append `| readfile` to read the content of the file",
             default = {},
         ),
         "templates": attr.label_list(

helm/private/packager/packager.go

@@ -357,6 +357,21 @@ func replaceKeyValues(content string, replacementGroups []ReplacementGroup, must
 	return content, nil
 }
 
+func readFileIfExists(path string) (string, error) {
+	if strings.HasSuffix(path, "| readfile") {
+		path = strings.TrimSpace(strings.TrimSuffix(path, "| readfile"))
+
+		content, err := os.ReadFile(path)
+		if err != nil {
+			return "", fmt.Errorf("Error reading file %s: %w", path, err)
+		}
+
+		return string(content), nil
+	} else {
+		return path, nil
+	}
+}
+
 func applySubstitutions(content string, substitutions_file string) (string, error) {
 	if len(substitutions_file) == 0 {
 		return content, nil
@@ -374,8 +389,11 @@ func applySubstitutions(content string, substitutions_file string) (string, erro
 	}
 
 	for key, val := range substitutions {
-		replaceKey := fmt.Sprintf("{%s}", key)
-		content = strings.ReplaceAll(content, replaceKey, val)
+		replacmentValue, err := readFileIfExists(val)
+		if err != nil {
+			return "", fmt.Errorf("Error reading file %s: %w", val, err)
+		}
+		content = strings.ReplaceAll(content, key, replacmentValue)
 	}
 
 	return content, nil

tests/substitutions/.gitignore

@@ -0,0 +1 @@
+charts

tests/substitutions/.helmignore

@@ -0,0 +1,23 @@
+# Patterns to ignore when building packages.
+# This supports shell glob matching, relative path matching, and
+# negation (prefixed with !). Only one pattern per line.
+.DS_Store
+# Common VCS dirs
+.git/
+.gitignore
+.bzr/
+.bzrignore
+.hg/
+.hgignore
+.svn/
+# Common backup files
+*.swp
+*.bak
+*.tmp
+*.orig
+*~
+# Various IDEs
+.project
+.idea/
+*.tmproj
+.vscode/

tests/substitutions/BUILD.bazel

@@ -0,0 +1,51 @@
+load("@rules_oci//oci:defs.bzl", "oci_image", "oci_push")
+load("//helm:defs.bzl", "helm_chart", "helm_lint_test", "helm_template_test")
+load("//tests:test_defs.bzl", "helm_package_regex_test")
+
+EXCLUDE_WINDOWS = select({
+    # TODO: rules_oci is broken on simple windows systems such as the windows github runners
+    # https://github.com/abrisco/rules_helm/issues/53
+    "@platforms//os:windows": ["@platforms//:incompatible"],
+    "//conditions:default": [],
+})
+
+oci_image(
+    name = "image",
+    base = "@rules_helm_test_container_base",
+    target_compatible_with = EXCLUDE_WINDOWS,
+)
+
+helm_chart(
+    name = "substitutions",
+    chart = "Chart.yaml",
+    data = [
+        ":image.digest",
+    ],
+    registry_url = "oci://localhost/helm-registry",
+    substitutions = {
+        "this_should_be_replaced": "replacement_value",
+        "image_sha256": "$(execpath :image.digest) | readfile",
+    },
+    values = "values.yaml",
+    visibility = ["//tests/with_chart_deps:__subpackages__"],
+)
+
+helm_lint_test(
+    name = "substitutions_lint_test",
+    chart = ":substitutions",
+)
+
+helm_template_test(
+    name = "substitutions_template_test",
+    chart = ":substitutions",
+)
+
+helm_package_regex_test(
+    name = "substitutions_regex_test",
+    package = ":substitutions",
+    target_compatible_with = EXCLUDE_WINDOWS,
+    values_patterns = [
+        r"replacement_value",
+        r"sha256:54bee42e3bf22cd1781f5cbc1e1cc9b5cff1d6766355148d66b90f09e9936db3",
+    ],
+)

tests/substitutions/Chart.yaml

@@ -0,0 +1,24 @@
+apiVersion: v2
+name: substitutions
+description: A Helm chart for Kubernetes
+
+# A chart can be either an 'application' or a 'library' chart.
+#
+# Application charts are a collection of templates that can be packaged into versioned archives
+# to be deployed.
+#
+# Library charts provide useful utilities or functions for the chart developer. They're included as
+# a dependency of application charts to inject those utilities and functions into the rendering
+# pipeline. Library charts do not define any templates and therefore cannot be deployed.
+type: application
+
+# This is the chart version. This version number should be incremented each time you make changes
+# to the chart and its templates, including the app version.
+# Versions are expected to follow Semantic Versioning (https://semver.org/)
+version: 0.1.0
+
+# This is the version number of the application being deployed. This version number should be
+# incremented each time you make changes to the application. Versions are not expected to
+# follow Semantic Versioning. They should reflect the version the application is using.
+# It is recommended to use it with quotes.
+appVersion: "1.16.0"

tests/substitutions/templates/deployment.yaml

@@ -0,0 +1,18 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: test
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: test
+  template:
+    metadata:
+      labels:
+        app: test
+    spec:
+      containers:
+        - name: {{ .Values.stringReplacment }}
+          image: "nginx@{{ .Values.image.sha256 }}"
+          imagePullPolicy: IfNotPresent

tests/substitutions/values.yaml

@@ -0,0 +1,10 @@
+# Default values for simple.
+# This is a YAML-formatted file.
+# Declare variables to be passed into your templates.
+
+replicaCount: 1
+
+stringReplacment: this_should_be_replaced
+
+image:
+  sha256: {image_sha256}