From 4524d12648534382208e11fb4976c6e1c9990a77 Mon Sep 17 00:00:00 2001
From: Ids van der Molen <ids@idsvandermolen.com>
Date: Sat, 17 Oct 2020 12:06:48 +0200
Subject: [PATCH] feat(controller): Allow whitespace in variable substitution.
 Fixes #4286

---
 docs/variables.md            |  6 +++---
 workflow/common/util.go      |  2 +-
 workflow/common/util_test.go | 14 ++++++++++++++
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/docs/variables.md b/docs/variables.md
index 3145542d6271..5a0c1db95789 100644
--- a/docs/variables.md
+++ b/docs/variables.md
@@ -1,9 +1,9 @@
 # Workflow Variables
 
-Some fields in a workflow specification allow for variable references which are automatically substituted by Argo. 
+Some fields in a workflow specification allow for variable references which are automatically substituted by Argo.
 
 ??? note "How to use variables"
-    Variables are enclosed in curly braces and **must not** include whitespace.
+    Variables are enclosed in curly braces and **may** include whitespace between the brackets and variable.
 
     ``` yaml
     apiVersion: argoproj.io/v1alpha1
@@ -24,7 +24,7 @@ Some fields in a workflow specification allow for variable references which are
         container:
           image: docker/whalesay
           command: [cowsay]
-        # args: ["{{ inputs.parameters.message }}"]       <- bad
+        # args: ["{{ inputs.parameters.message }}"]       <- good
           args: ["{{inputs.parameters.message}}"]         #  good
     ```
 
diff --git a/workflow/common/util.go b/workflow/common/util.go
index 0e6e36cc92f5..ffca81d8a67e 100644
--- a/workflow/common/util.go
+++ b/workflow/common/util.go
@@ -373,7 +373,7 @@ func SubstituteParams(tmpl *wfv1.Template, globalParams, localParams Parameters)
 func Replace(fstTmpl *fasttemplate.Template, replaceMap map[string]string, allowUnresolved bool) (string, error) {
 	var unresolvedErr error
 	replacedTmpl := fstTmpl.ExecuteFuncString(func(w io.Writer, tag string) (int, error) {
-		replacement, ok := replaceMap[tag]
+		replacement, ok := replaceMap[strings.TrimSpace(tag)]
 		if !ok {
 			// Attempt to resolve nested tags, if possible
 			if index := strings.LastIndex(tag, "{{"); index > 0 {
diff --git a/workflow/common/util_test.go b/workflow/common/util_test.go
index 0b66a00c7b9a..13f741d62d5d 100644
--- a/workflow/common/util_test.go
+++ b/workflow/common/util_test.go
@@ -157,3 +157,17 @@ func TestNestedReplaceString(t *testing.T) {
 		}
 	}
 }
+
+func TestReplaceStringWithWhiteSpace(t *testing.T) {
+
+	replaceMap := map[string]string{"inputs.parameters.message": "hello world"}
+
+	test := `{{ inputs.parameters.message }}`
+	fstTmpl, err := fasttemplate.NewTemplate(test, "{{", "}}")
+	if assert.NoError(t, err) {
+		replacement, err := Replace(fstTmpl, replaceMap, true)
+		if assert.NoError(t, err) {
+			assert.Equal(t, "hello world", replacement)
+		}
+	}
+}