From 6a779d07d0d7d2cd036b6c3b54d3d30d322cb145 Mon Sep 17 00:00:00 2001
From: Steve Boyd <emteknetnz@gmail.com>
Date: Thu, 12 May 2022 17:12:14 +1200
Subject: [PATCH] ENH Allow multiple backtick variables in a single value

---
 .../03_Environment_Management.md              |  7 +++--
 src/Core/Injector/Injector.php                | 31 ++++++++++++++-----
 tests/php/Core/Injector/InjectorTest.php      | 27 ++++++++++++++++
 3 files changed, 55 insertions(+), 10 deletions(-)

diff --git a/docs/en/00_Getting_Started/03_Environment_Management.md b/docs/en/00_Getting_Started/03_Environment_Management.md
index 869ed26e0..aa87a727d 100644
--- a/docs/en/00_Getting_Started/03_Environment_Management.md
+++ b/docs/en/00_Getting_Started/03_Environment_Management.md
@@ -58,13 +58,16 @@ Environment::setEnv('API_KEY', 'AABBCCDDEEFF012345');
 
 ### Using environment variables in config
 
-To use environment variables in `.yaml` configs you can reference them using backticks.
+To use environment variables in `.yaml` configs you can reference them using backticks. You can have multiple
+environment variables within a single value, though the overall value must start and end with backticks.
 
 ```yaml
 SilverStripe\Core\Injector\Injector:
     MyServiceClass:
         properties:
-            MyProperty: '`ENV_VAR_HERE`'
+            MyProperty: '`ENV_VAR_ONE`'
+            MultiValueProperty: '`ENV_VAR_ONE`:`ENV_VAR_TWO`'
+            ThisWillNotSubstitute: 'lorem `REGULAR_TEXT` ipsum'
 ```
 
 [info]
diff --git a/src/Core/Injector/Injector.php b/src/Core/Injector/Injector.php
index 98da89a2c..f5b4b87c8 100644
--- a/src/Core/Injector/Injector.php
+++ b/src/Core/Injector/Injector.php
@@ -524,16 +524,31 @@ class Injector implements ContainerInterface
         }
 
         // Evaluate constants surrounded by back ticks
-        if (preg_match('/^`(?<name>[^`]+)`$/', $value ?? '', $matches)) {
-            $envValue = Environment::getEnv($matches['name']);
-            if ($envValue !== false) {
-                $value = $envValue;
-            } elseif (defined($matches['name'] ?? '')) {
-                $value = constant($matches['name'] ?? '');
-            } else {
-                $value = null;
+        $hasBacticks = false;
+        $allMissing = true;
+        // $value must start and end with backticks, though there can be multiple
+        // things being subsituted within $value e.g. "`VAR_ONE`:`VAR_TWO`:`VAR_THREE`"
+        if (preg_match('/^`.+`$/', $value ?? '')) {
+            $hasBacticks = true;
+            preg_match_all('/`(?<name>[^`]+)`/', $value, $matches);
+            foreach ($matches['name'] as $name) {
+                $envValue = Environment::getEnv($name);
+                $val = '';
+                if ($envValue !== false) {
+                    $val = $envValue;
+                } elseif (defined($name)) {
+                    $val = constant($name);
+                }
+                $value = str_replace("`$name`", $val, $value);
+                if ($val) {
+                    $allMissing = false;
+                }
             }
         }
+        // silverstripe sometimes explictly expects a null value rather than just an empty string
+        if ($hasBacticks && $allMissing && $value === '') {
+            return null;
+        }
 
         return $value;
     }
diff --git a/tests/php/Core/Injector/InjectorTest.php b/tests/php/Core/Injector/InjectorTest.php
index e9b8b6db4..3b8cd1850 100644
--- a/tests/php/Core/Injector/InjectorTest.php
+++ b/tests/php/Core/Injector/InjectorTest.php
@@ -3,6 +3,7 @@
 namespace SilverStripe\Core\Tests\Injector;
 
 use SilverStripe\Core\Config\Config;
+use SilverStripe\Core\Environment;
 use SilverStripe\Core\Injector\Factory;
 use SilverStripe\Core\Injector\Injector;
 use SilverStripe\Core\Injector\InjectorNotFoundException;
@@ -815,6 +816,32 @@ class InjectorTest extends SapphireTest
         $this->assertInstanceOf(OtherTestObject::class, $item->property->property);
     }
 
+    /**
+     * @dataProvider provideConvertServicePropertyBackTicks
+     */
+    public function testConvertServicePropertyBackTicks($value, $expected)
+    {
+        Environment::setEnv('INJECTOR_TEST_CSP_A', 'ABC');
+        Environment::setEnv('INJECTOR_TEST_CSP_B', 'DEF');
+        Environment::setEnv('INJECTOR_TEST_CSP_C', 'GHI');
+        $actual = Injector::inst()->convertServiceProperty($value);
+        $this->assertSame($expected, $actual);
+    }
+
+    public function provideConvertServicePropertyBackTicks()
+    {
+        return [
+            ['`INJECTOR_TEST_CSP_A`', 'ABC'],
+            ['`INJECTOR_TEST_CSP_A`:`INJECTOR_TEST_CSP_B`', 'ABC:DEF'],
+            ['`INJECTOR_TEST_CSP_A` some text `INJECTOR_TEST_CSP_B`', 'ABC some text DEF'],
+            ['`INJECTOR_TEST_CSP_A``INJECTOR_TEST_CSP_B`', 'ABCDEF'],
+            ['`INJECTOR_TEST_CSP_A`:`INJECTOR_TEST_CSP_B``INJECTOR_TEST_CSP_C`', 'ABC:DEFGHI'],
+            ['`INJECTOR_TEST_CSP_A`:`INJECTOR_TEST_CSP_X`', 'ABC:'],
+            ['`INJECTOR_TEST_CSP_X`', null],
+            ['lorem `INJECTOR_TEST_CSP_A` ipsum', 'lorem `INJECTOR_TEST_CSP_A` ipsum'],
+        ];
+    }
+
     public function testNamedServices()
     {
         $injector = new Injector();