fix: pass --kube-context to helm template when using jsonPatches (#2363)

fix: pass --kube-context to helm template when using jsonPatches (#2309)

When using jsonPatches or strategicMergePatches in helmfile, the
`helm template` command was not receiving the `--kube-context` flag.
This caused issues when `--dry-run=server` was used (introduced in
PR #2271 to support lookup() functions), because helm would connect
to the wrong cluster context.

Root Cause:
1. `flagsForTemplate()` did not call `appendConnectionFlags()`, unlike
   `flagsForUpgrade()` and `flagsForDiff()` which both include this call.
2. `processChartification()` did not include `--kube-context` when
   setting `chartifyOpts.TemplateArgs` for internal helm template calls.

Fix:
1. Added `appendConnectionFlags()` call to `flagsForTemplate()` to ensure
   kube-context and other connection flags are passed to helm template.
2. Added `getKubeContext()` helper function that resolves kube-context
   with proper priority: release > environment > helmDefaults.
3. Modified `processChartification()` to include `--kube-context` in
   chartifyOpts.TemplateArgs when chartify needs to run helm template.
4. Added compatibility check for `--validate` flag to avoid Helm 4
   mutual exclusion error between --validate and --dry-run (Issue #2355).

Fixes #2309

Signed-off-by: Aditya Menon <amenon@canarytechnologies.com>

test/integration/run.sh

@@ -119,6 +119,7 @@ ${kubectl} create namespace ${test_ns} || fail "Could not create namespace ${tes
 . ${dir}/test-cases/issue-2291.sh
 . ${dir}/test-cases/oci-parallel-pull.sh
 . ${dir}/test-cases/issue-2297-local-chart-transformers.sh
+. ${dir}/test-cases/issue-2309-kube-context-template.sh
 
 # ALL DONE -----------------------------------------------------------------------------------------------------------
 

test/integration/test-cases/issue-2309-kube-context-template.sh

@@ -0,0 +1,32 @@
+# Issue #2309: Test that helm template receives --kube-context when using jsonPatches
+# https://github.com/helmfile/helmfile/issues/2309
+#
+# This test verifies that helmfile correctly passes --kube-context to helm template
+# when helmDefaults.kubeContext is set and jsonPatches are used.
+
+issue_2309_case_input_dir="${cases_dir}/issue-2309-kube-context-template/input"
+issue_2309_case_output_dir="${cases_dir}/issue-2309-kube-context-template/output"
+
+config_file="helmfile.yaml.gotmpl"
+issue_2309_tmp=$(mktemp -d)
+issue_2309_template_output=${issue_2309_tmp}/issue_2309.template.log
+
+test_start "helmfile template with kube-context and jsonPatches (issue #2309)"
+
+info "Running helmfile template with kubeContext and jsonPatches"
+${helmfile} -f ${issue_2309_case_input_dir}/${config_file} template > ${issue_2309_template_output} || fail "\"helmfile template\" shouldn't fail"
+
+info "Checking template output"
+cat ${issue_2309_template_output}
+
+# Verify the output contains the patched ConfigMap
+if grep -q "patched: \"true\"" ${issue_2309_template_output}; then
+    info "Found patched value in output - jsonPatches applied successfully"
+else
+    fail "jsonPatches were not applied - missing 'patched: true' in output"
+fi
+
+# Compare with expected output
+./dyff between -bs ${issue_2309_case_output_dir}/template ${issue_2309_template_output} || fail "\"helmfile template\" output should match expected"
+
+test_pass "helmfile template with kube-context and jsonPatches (issue #2309)"

test/integration/test-cases/issue-2309-kube-context-template/input/helmfile.yaml.gotmpl

@@ -0,0 +1,30 @@
+# Issue #2309: helm template should receive --kube-context when using jsonPatches
+# https://github.com/helmfile/helmfile/issues/2309
+helmDefaults:
+  kubeContext: test-context
+
+repositories:
+- name: incubator
+  url: https://charts.helm.sh/incubator
+---
+releases:
+- name: test-release
+  chart: incubator/raw
+  namespace: default
+  values:
+  - resources:
+    - apiVersion: v1
+      kind: ConfigMap
+      metadata:
+        name: test-configmap
+      data:
+        key: value
+  jsonPatches:
+    - target:
+        version: v1
+        kind: ConfigMap
+        name: test-configmap
+      patch:
+      - op: add
+        path: /data/patched
+        value: "true"

test/integration/test-cases/issue-2309-kube-context-template/output/template

@@ -0,0 +1,15 @@
+---
+# Source: raw/templates/patched_resources.yaml
+apiVersion: v1
+data:
+  key: value
+  patched: "true"
+kind: ConfigMap
+metadata:
+  labels:
+    app: raw
+    chart: raw-0.2.5
+    heritage: Helm
+    release: test-release
+  name: test-configmap
+