From 66f2306bb4ddf0794f92360c35783c1941df30c8 Mon Sep 17 00:00:00 2001
From: Ids van der Molen <ids@idsvandermolen.com>
Date: Sat, 17 Oct 2020 16:58:52 +0200
Subject: [PATCH] feat(controller): Allow whitespace in variable substitution.
 Fixes #4286 (#4310)

---
 docs/variables.md            | 28 ++++++++++++++++++++++++++++
 workflow/common/util.go      |  2 +-
 workflow/common/util_test.go | 14 ++++++++++++++
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/docs/variables.md b/docs/variables.md
index 24b5fbb50ecf..149bb6b5aa1f 100644
--- a/docs/variables.md
+++ b/docs/variables.md
@@ -1,5 +1,33 @@
 # Workflow Variables
 
+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 **may** include whitespace between the brackets and variable.
+
+    ``` yaml
+    apiVersion: argoproj.io/v1alpha1
+    kind: Workflow
+    metadata:
+      generateName: hello-world-parameters-
+    spec:
+      entrypoint: whalesay
+      arguments:
+        parameters:
+        - name: message
+          value: hello world
+      templates:
+      - name: whalesay
+        inputs:
+          parameters:
+          - name: message
+        container:
+          image: docker/whalesay
+          command: [cowsay]
+        # args: ["{{ inputs.parameters.message }}"]       <- good
+          args: ["{{inputs.parameters.message}}"]         #  good
+    ```
+
 The following variables are made available to reference various metadata of a workflow:
 
 ## All Templates
diff --git a/workflow/common/util.go b/workflow/common/util.go
index 4d32e146d8e2..b09f630a0c2a 100644
--- a/workflow/common/util.go
+++ b/workflow/common/util.go
@@ -372,7 +372,7 @@ 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)
+		}
+	}
+}