feat(controller): Allow whitespace in variable substitution. Fixes ar…

…goproj#4286

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
     ```
 

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 {

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)
+		}
+	}
+}