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matkammatkam
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feat: additional template functions (#3949)
* additional template functions * lint * fix typeo * status check fixes * lint fix try 2 * lint fix try 3 * tests for individual functions
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‎docs/advanced/fqdn-templating.md‎

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@@ -68,6 +68,9 @@ The template uses the following data from the source object (e.g., a `Service` o
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| Function | Description |
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|:-------------|:-----------------------------------------------------------------------------------------|
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| `trimPrefix` | Function from the `strings` package. Returns `string` without the provided leading prefix. |
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| `replace` | Function that performs a simple replacement of all `old` string with `new` in the source string. |
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| `isIPv4` | Function that checks if a string is a valid IPv4 address. |
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| `isIPv6` | Function that checks if a string is a valid IPv6 address (including IPv4-mapped IPv6). |
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---
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@@ -304,3 +307,12 @@ args:
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```
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By setting the hostname annotation in the ingress resource, ExternalDNS constructs the FQDN accordingly. This approach allows for dynamic DNS entries without hardcoding hostnames.
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### Using a Node's Addresses for FQDNs
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```yml
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args:
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- --fqdn-template="{{range .Status.Addresses}}{{if and (eq .Type \"ExternalIP\") (isIPv4 .Address)}}{{.Address | replace \".\" \"-\"}}{{break}}{{end}}{{end}}.example.com
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```
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This is a complex template that iternates through a list of a Node's Addresses and creates a FQDN with public IPv4 addresses.

‎source/fqdn/fqdn.go‎

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@@ -17,6 +17,7 @@ limitations under the License.
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package fqdn
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import (
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"net/netip"
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"strings"
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"text/template"
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)
@@ -27,6 +28,34 @@ func ParseTemplate(fqdnTemplate string) (tmpl *template.Template, err error) {
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}
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funcs := template.FuncMap{
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"trimPrefix": strings.TrimPrefix,
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"replace": replace,
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"isIPv6": isIPv6String,
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"isIPv4": isIPv4String,
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}
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return template.New("endpoint").Funcs(funcs).Parse(fqdnTemplate)
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}
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// replace all instances of oldValue with newValue in target string.
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// adheres to syntax from https://masterminds.github.io/sprig/strings.html.
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func replace(oldValue, newValue, target string) string {
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return strings.ReplaceAll(target, oldValue, newValue)
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}
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// isIPv6String reports whether the target string is an IPv6 address,
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// including IPv4-mapped IPv6 addresses.
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func isIPv6String(target string) bool {
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netIP, err := netip.ParseAddr(target)
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if err != nil {
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return false
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}
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return netIP.Is6()
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}
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// isIPv4String reports whether the target string is an IPv4 address.
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func isIPv4String(target string) bool {
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netIP, err := netip.ParseAddr(target)
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if err != nil {
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return false
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}
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return netIP.Is4()
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}

‎source/fqdn/fqdn_test.go‎

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@@ -60,6 +60,31 @@ func TestParseTemplate(t *testing.T) {
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expectError: false,
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annotationFilter: "kubernetes.io/ingress.class=nginx",
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},
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{
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name: "replace template function",
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expectError: false,
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fqdnTemplate: "{{\"hello.world\" | replace \".\" \"-\"}}.ext-dns.test.com",
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},
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{
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name: "isIPv4 template function with valid IPv4",
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expectError: false,
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fqdnTemplate: "{{if isIPv4 \"192.168.1.1\"}}valid{{else}}invalid{{end}}.ext-dns.test.com",
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},
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{
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name: "isIPv4 template function with invalid IPv4",
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expectError: false,
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fqdnTemplate: "{{if isIPv4 \"not.an.ip.addr\"}}valid{{else}}invalid{{end}}.ext-dns.test.com",
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},
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{
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name: "isIPv6 template function with valid IPv6",
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expectError: false,
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fqdnTemplate: "{{if isIPv6 \"2001:db8::1\"}}valid{{else}}invalid{{end}}.ext-dns.test.com",
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},
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{
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name: "isIPv6 template function with invalid IPv6",
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expectError: false,
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fqdnTemplate: "{{if isIPv6 \"not:ipv6:addr\"}}valid{{else}}invalid{{end}}.ext-dns.test.com",
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},
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} {
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t.Run(tt.name, func(t *testing.T) {
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_, err := ParseTemplate(tt.fqdnTemplate)
@@ -71,3 +96,130 @@ func TestParseTemplate(t *testing.T) {
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})
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}
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}
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func TestReplace(t *testing.T) {
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for _, tt := range []struct {
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name string
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oldValue string
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newValue string
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target string
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expected string
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}{
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{
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name: "simple replacement",
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oldValue: "old",
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newValue: "new",
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target: "old-value",
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expected: "new-value",
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},
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{
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name: "multiple replacements",
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oldValue: ".",
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newValue: "-",
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target: "hello.world.com",
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expected: "hello-world-com",
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},
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{
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name: "no replacement needed",
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oldValue: "x",
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newValue: "y",
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target: "hello-world",
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expected: "hello-world",
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},
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{
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name: "empty strings",
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oldValue: "",
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newValue: "",
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target: "test",
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expected: "test",
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},
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} {
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t.Run(tt.name, func(t *testing.T) {
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result := replace(tt.oldValue, tt.newValue, tt.target)
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assert.Equal(t, tt.expected, result)
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})
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}
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}
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func TestIsIPv6String(t *testing.T) {
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for _, tt := range []struct {
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name string
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input string
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expected bool
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}{
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{
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name: "valid IPv6",
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input: "2001:db8::1",
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expected: true,
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},
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{
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name: "valid IPv6 with multiple segments",
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input: "2001:0db8:85a3:0000:0000:8a2e:0370:7334",
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expected: true,
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},
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{
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name: "valid IPv4-mapped IPv6",
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input: "::ffff:192.168.1.1",
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expected: true,
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},
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{
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name: "invalid IPv6",
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input: "not:ipv6:addr",
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expected: false,
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},
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{
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name: "IPv4 address",
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input: "192.168.1.1",
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expected: false,
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},
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{
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name: "empty string",
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input: "",
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expected: false,
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},
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} {
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t.Run(tt.name, func(t *testing.T) {
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result := isIPv6String(tt.input)
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assert.Equal(t, tt.expected, result)
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})
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}
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}
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func TestIsIPv4String(t *testing.T) {
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for _, tt := range []struct {
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name string
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input string
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expected bool
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}{
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{
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name: "valid IPv4",
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input: "192.168.1.1",
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expected: true,
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},
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{
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name: "invalid IPv4",
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input: "256.256.256.256",
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expected: false,
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},
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{
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name: "IPv6 address",
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input: "2001:db8::1",
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expected: false,
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},
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{
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name: "invalid format",
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input: "not.an.ip",
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expected: false,
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},
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{
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name: "empty string",
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input: "",
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expected: false,
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},
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} {
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t.Run(tt.name, func(t *testing.T) {
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result := isIPv4String(tt.input)
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assert.Equal(t, tt.expected, result)
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})
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}
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}

‎source/node_test.go‎

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@@ -66,6 +66,11 @@ func testNodeSourceNewNodeSource(t *testing.T) {
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expectError: false,
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fqdnTemplate: "{{.Name}}-{{.Namespace}}.ext-dns.test.com",
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},
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{
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title: "complex template",
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expectError: false,
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fqdnTemplate: "{{range .Status.Addresses}}{{if and (eq .Type \"ExternalIP\") (isIPv4 .Address)}}{{.Address | replace \".\" \"-\"}}{{break}}{{end}}{{end}}.ext-dns.test.com",
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},
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{
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title: "non-empty annotation filter label",
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expectError: false,

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