Updated the regex to include spaces around null propagation operator for readability, updated the tests & docs

Author: ruhullahshah

docs/configuration.md

@@ -75,7 +75,7 @@ attributes. Valid values: `MajorMinorPatchTag`, `MajorMinorPatch`, `MajorMinor`,
 Set this to any of the available [variables](/more-info/variables) in combination (but not necessary) with
 a process scoped environment variable. It overwrites the value of `assembly-file-versioning-scheme`. To reference
 an environment variable, use `env:`
-Example Syntax #1: `'{Major}.{Minor}.{Patch}.{env:JENKINS_BUILD_NUMBER??fallback_string}'`. Uses `JENKINS_BUILD_NUMBER`
+Example Syntax #1: `'{Major}.{Minor}.{Patch}.{env:JENKINS_BUILD_NUMBER ?? fallback_string}'`. Uses `JENKINS_BUILD_NUMBER`
 if available in the environment otherwise the `fallback_string`
 Example Syntax #2: `'{Major}.{Minor}.{Patch}.{env:JENKINS_BUILD_NUMBER}'`.  Uses `JENKINS_BUILD_NUMBER`
 if available in the environment otherwise the parsing fails.

src/GitVersionCore.Tests/StringFormatWithExtensionTests.cs

@@ -55,7 +55,7 @@ public void FormatWith_EnvVarTokenWithFallback()
         {
             Environment.SetEnvironmentVariable("GIT_VERSION_TEST_VAR", "Env Var Value");
             var propertyObject = new { };
-            var target = "{env:GIT_VERSION_TEST_VAR??fallback}";
+            var target = "{env:GIT_VERSION_TEST_VAR ?? fallback}";
             var expected = "Env Var Value";
             var actual = target.FormatWith(propertyObject);
             Assert.AreEqual(expected, actual);
@@ -66,7 +66,7 @@ public void FormatWith_UnsetEnvVarTokenWithFallback()
         {
             Environment.SetEnvironmentVariable("GIT_VERSION_UNSET_TEST_VAR", null);
             var propertyObject = new { };
-            var target = "{env:GIT_VERSION_UNSET_TEST_VAR??fallback}";
+            var target = "{env:GIT_VERSION_UNSET_TEST_VAR ?? fallback}";
             var expected = "fallback";
             var actual = target.FormatWith(propertyObject);
             Assert.AreEqual(expected, actual);
@@ -89,7 +89,7 @@ public void FormatWith_MultipleEnvChars()
         {
             var propertyObject = new { };
             //Test the greediness of the regex in matching env: char
-            var target = "{env:env:GIT_VERSION_TEST_VAR_1} and {env:DUMMY_VAR??fallback}";
+            var target = "{env:env:GIT_VERSION_TEST_VAR_1} and {env:DUMMY_VAR ?? fallback}";
             var expected = "{env:env:GIT_VERSION_TEST_VAR_1} and fallback";
             var actual = target.FormatWith(propertyObject);
             Assert.AreEqual(expected, actual);
@@ -100,7 +100,7 @@ public void FormatWith_MultipleFallbackChars()
         {
             var propertyObject = new { };
             //Test the greediness of the regex in matching env: and ?? chars
-            var target = "{env:env:GIT_VERSION_TEST_VAR_1} and {env:DUMMY_VAR???fallback}";
+            var target = "{env:env:GIT_VERSION_TEST_VAR_1} and {env:DUMMY_VAR ??? fallback}";
             var actual = target.FormatWith(propertyObject);
             Assert.AreEqual(target, actual);
         }
@@ -111,9 +111,19 @@ public void FormatWith_SingleFallbackChar()
             Environment.SetEnvironmentVariable("DUMMY_ENV_VAR", "Dummy-Val");
             var propertyObject = new { };
             //Test the sanity of the regex when there is a grammar mismatch
-            var target = "{en:DUMMY_ENV_VAR} and {env:DUMMY_ENV_VAR?fallback}";
+            var target = "{en:DUMMY_ENV_VAR} and {env:DUMMY_ENV_VAR??fallback}";
             var actual = target.FormatWith(propertyObject);
             Assert.AreEqual(target, actual);
         }
+
+        [Test]
+        public void FormatWIth_NullPropagationWithMultipleSpaces()
+        {
+            var propertyObject = new { SomeProperty = "Some Value" };
+            var target = "{SomeProperty} and {env:DUMMY_ENV_VAR  ??  fallback}";
+            var expected = "Some Value and fallback";
+            var actual = target.FormatWith(propertyObject);
+            Assert.AreEqual(expected, actual);
+        }
     }
 }

src/GitVersionCore/StringFormatWith.cs

@@ -8,7 +8,7 @@ namespace GitVersion
 
     static class StringFormatWithExtension
     {
-        private static readonly Regex TokensRegex = new Regex(@"{(env:)??\w+(\?\?\w+)??}", RegexOptions.Compiled);
+        private static readonly Regex TokensRegex = new Regex(@"{(env:)??\w+(\s+(\?\?)??\s+\w+)??}", RegexOptions.Compiled);
 
         /// <summary>
         ///     Formats a string template with the given source object.
@@ -43,8 +43,8 @@ public static string FormatWith<T>(this string template, T source)
                     string[] components = (memberAccessExpression.Contains("??")) ? memberAccessExpression.Split(new string[] { "??" }, StringSplitOptions.None) : null;
                     if (components != null)
                     {
-                        envVar = components[0];
-                        fallback = components[1];
+                        envVar = components[0].Trim();
+                        fallback = components[1].Trim();
                     }
 
                     propertyValue = Helpers.EnvironmentHelper.GetEnvironmentVariableForProcess(envVar);