docs: retry docs improvement (#8794)

* docs: fix retryStrategy.expression in comments

Signed-off-by: John Lin <johnlinp@gmail.com>

* docs: add a description to mark OnFailure as the default for retryPolicy

Signed-off-by: John Lin <johnlinp@gmail.com>

* docs: retryStrategy.expression overrides retryStrategy.retryPolicy

Signed-off-by: John Lin <johnlinp@gmail.com>

docs/retries.md

@@ -27,7 +27,7 @@ spec:
 Use `retryPolicy` to choose which failures to retry:
 
 - `Always`: Retry all failed steps
-- `OnFailure`: Retry steps whose main container is marked as failed in Kubernetes
+- `OnFailure`: Retry steps whose main container is marked as failed in Kubernetes (this is the default)
 - `OnError`: Retry steps that encounter Argo controller errors, or whose init or wait containers fail
 - `OnTransientError`: Retry steps that encounter errors [defined as transient](https://github.com/argoproj/argo-workflows/blob/master/util/errors/errors.go), or errors matching the `TRANSIENT_ERROR_PATTERN` [environment variable](https://argoproj.github.io/argo-workflows/environment-variables/). Available in version 3.0 and later.
 
@@ -66,6 +66,8 @@ access to the following variables:
 
 If `expression` evaluates to false, the step will not be retried.
 
+Note that when `expression` is specified, `retryPolicy` will be ignored.
+
 See [example](https://raw.githubusercontent.com/argoproj/argo-workflows/master/examples/retry-conditional.yaml) for usage.
 
 ## Back-Off

examples/retry-conditional.yaml

@@ -1,4 +1,4 @@
-# Only retry if the retryStrategy.when condition is satisfied. In this example, retries will be made until a pod has
+# Only retry if the retryStrategy.expression condition is satisfied. In this example, retries will be made until a pod has
 # exit code 2 or the limit of 10 is reached, whichever happens first.
 apiVersion: argoproj.io/v1alpha1
 kind: Workflow

workflow/controller/operator_test.go

@@ -7545,7 +7545,7 @@ status:
   startedAt: "2021-06-10T22:28:49Z"
 `
 
-// TestOperatorRetryExpression tests that retryStrategy.when works correctly. In this test, the latest child node has
+// TestOperatorRetryExpression tests that retryStrategy.expression works correctly. In this test, the latest child node has
 // just failed with exit code 2. The retryStrategy's when condition specifies that retries must only be done when the
 // last exit code is NOT 2. We expect the retryStrategy to fail (even though it has 8 tries remainng).
 func TestOperatorRetryExpression(t *testing.T) {