From 7d6923730e34e9005e6a607ccd247d96f7a96bea Mon Sep 17 00:00:00 2001
From: TwiN <twin@linux.com>
Date: Sat, 11 Feb 2023 22:43:13 -0500
Subject: [PATCH] fix(config): Support `$$` in config for literal `$` (#427)

---
 config/config.go      |  6 ++++++
 config/config_test.go | 29 ++++++++++++++++++++++++++++-
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/config/config.go b/config/config.go
index 48bc7a2e..1f2d2051 100644
--- a/config/config.go
+++ b/config/config.go
@@ -7,6 +7,7 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 
 	"github.com/TwiN/deepmerge"
@@ -214,8 +215,13 @@ func walkConfigDir(path string, fn fs.WalkDirFunc) error {
 
 // parseAndValidateConfigBytes parses a Gatus configuration file into a Config struct and validates its parameters
 func parseAndValidateConfigBytes(yamlBytes []byte) (config *Config, err error) {
+	// Replace $$ with __GATUS_LITERAL_DOLLAR_SIGN__ to prevent os.ExpandEnv from treating "$$" as if it was an
+	// environment variable. This allows Gatus to support literal "$" in the configuration file.
+	yamlBytes = []byte(strings.ReplaceAll(string(yamlBytes), "$$", "__GATUS_LITERAL_DOLLAR_SIGN__"))
 	// Expand environment variables
 	yamlBytes = []byte(os.ExpandEnv(string(yamlBytes)))
+	// Replace __GATUS_LITERAL_DOLLAR_SIGN__ with "$" to restore the literal "$" in the configuration file
+	yamlBytes = []byte(strings.ReplaceAll(string(yamlBytes), "__GATUS_LITERAL_DOLLAR_SIGN__", "$"))
 	// Parse configuration file
 	if err = yaml.Unmarshal(yamlBytes, &config); err != nil {
 		return
diff --git a/config/config_test.go b/config/config_test.go
index 1ab465c4..ef1068a7 100644
--- a/config/config_test.go
+++ b/config/config_test.go
@@ -1534,7 +1534,34 @@ endpoints:
 	}
 }
 
-func TestParseAndValidateConfigBytesWithNoEndpointsOrAutoDiscovery(t *testing.T) {
+func TestParseAndValidateConfigBytesWithLiteralDollarSign(t *testing.T) {
+	os.Setenv("GATUS_TestParseAndValidateConfigBytesWithLiteralDollarSign", "whatever")
+	config, err := parseAndValidateConfigBytes([]byte(`
+endpoints:
+  - name: website
+    url: https://twin.sh/health
+    conditions:
+      - "[BODY] == $$GATUS_TestParseAndValidateConfigBytesWithLiteralDollarSign"
+      - "[BODY] == $GATUS_TestParseAndValidateConfigBytesWithLiteralDollarSign"
+`))
+	if err != nil {
+		t.Error("expected no error, got", err.Error())
+	}
+	if config == nil {
+		t.Fatal("Config shouldn't have been nil")
+	}
+	if config.Endpoints[0].URL != "https://twin.sh/health" {
+		t.Errorf("URL should have been %s", "https://twin.sh/health")
+	}
+	if config.Endpoints[0].Conditions[0] != "[BODY] == $GATUS_TestParseAndValidateConfigBytesWithLiteralDollarSign" {
+		t.Errorf("Condition should have been %s", "[BODY] == $GATUS_TestParseAndValidateConfigBytesWithLiteralDollarSign")
+	}
+	if config.Endpoints[0].Conditions[1] != "[BODY] == whatever" {
+		t.Errorf("Condition should have been %s", "[BODY] == whatever")
+	}
+}
+
+func TestParseAndValidateConfigBytesWithNoEndpoints(t *testing.T) {
 	_, err := parseAndValidateConfigBytes([]byte(``))
 	if err != ErrNoEndpointInConfig {
 		t.Error("The error returned should have been of type ErrNoEndpointInConfig")