Ensure new provider is registered when provider diff is unknown (#4051)

The changes in #4004 caused old provider configuration to be used even when a provider was different between inputs and outputs, in the case that the diff returned DiffUnkown.

To better handle that case, we compute a more accurate (but still conservative) DiffNone or DiffSome so that we can ensure we conservatively update to a new provider when needed, but retain the performance benefit of not creating and configuring a new provider as much as possible.

Part of https://github.com/pulumi/pulumi-aws/issues/814.

CHANGELOG.md

@@ -2,15 +2,22 @@ CHANGELOG
 =========
 
 ## HEAD (Unreleased)
-* Fix Kubernetes YAML parsing error in .NET.
+- Fix Kubernetes YAML parsing error in .NET.
   [#4023](https://github.com/pulumi/pulumi/pull/4023)
+
 - Avoid projects beginning with `Pulumi` to stop cyclic imports
   [#4013](https://github.com/pulumi/pulumi/pull/4013)
+
 - Ensure we can locate Go created application binaries on Windows
   [#4030](https://github.com/pulumi/pulumi/pull/4030)
+
 - Ensure Python overlays work as part of our SDK generation
   [#4043](https://github.com/pulumi/pulumi/pull/4043)
 
+- Ensure old provider is not used when configuration has changed
+  [#4051](https://github.com/pulumi/pulumi/pull/4051)
+
+
 ## 1.12.0 (2020-03-04)
 - Avoid Configuring providers which are not used during preview.
   [#4004](https://github.com/pulumi/pulumi/pull/4004)

examples/multilang/python/Pulumi.luke-dev.yaml

@@ -0,0 +1,2 @@
+config:
+  aws:region: us-west-2

examples/multilang/python/mycomponent/pulumi_mycomponent.egg-info/PKG-INFO

@@ -0,0 +1,9 @@
+Metadata-Version: 2.1
+Name: pulumi-mycomponent
+Version: 0.0.1
+Summary: MyComponent
+Home-page: https://github.com/pulumi/pulumi
+License: Apache 2.0
+Description: # MyComponent in Python
+Platform: UNKNOWN
+Description-Content-Type: text/markdown

examples/multilang/python/mycomponent/pulumi_mycomponent.egg-info/SOURCES.txt

@@ -0,0 +1,8 @@
+README.md
+setup.py
+pulumi_mycomponent/__init__.py
+pulumi_mycomponent.egg-info/PKG-INFO
+pulumi_mycomponent.egg-info/SOURCES.txt
+pulumi_mycomponent.egg-info/dependency_links.txt
+pulumi_mycomponent.egg-info/not-zip-safe
+pulumi_mycomponent.egg-info/top_level.txt

examples/multilang/python/mycomponent/pulumi_mycomponent.egg-info/dependency_links.txt

@@ -0,0 +1 @@
+

examples/multilang/python/mycomponent/pulumi_mycomponent.egg-info/not-zip-safe

@@ -0,0 +1 @@
+

examples/multilang/python/mycomponent/pulumi_mycomponent.egg-info/top_level.txt

@@ -0,0 +1 @@
+pulumi_mycomponent

pkg/resource/deploy/providers/registry.go

@@ -295,6 +295,13 @@ func (r *Registry) Diff(urn resource.URN, id resource.ID, olds, news resource.Pr
 	if err != nil {
 		return plugin.DiffResult{Changes: plugin.DiffUnknown}, err
 	}
+	if diff.Changes == plugin.DiffUnknown {
+		if olds.DeepEquals(news) {
+			diff.Changes = plugin.DiffNone
+		} else {
+			diff.Changes = plugin.DiffSome
+		}
+	}
 
 	// If the diff requires replacement, unload the provider: the engine will reload it during its replacememnt Check.
 	//

pkg/resource/deploy/providers/registry_test.go

@@ -484,7 +484,7 @@ func TestCRUD(t *testing.T) {
 		// Diff
 		diff, err := r.Diff(urn, id, olds, news, false, nil)
 		assert.NoError(t, err)
-		assert.Equal(t, plugin.DiffResult{}, diff)
+		assert.Equal(t, plugin.DiffResult{Changes: plugin.DiffNone}, diff)
 
 		// The old provider should still be registered.
 		p2, ok := r.GetProvider(Reference{urn: urn, id: id})
@@ -613,7 +613,7 @@ func TestCRUDPreview(t *testing.T) {
 		// Diff
 		diff, err := r.Diff(urn, id, olds, news, false, nil)
 		assert.NoError(t, err)
-		assert.Equal(t, plugin.DiffResult{}, diff)
+		assert.Equal(t, plugin.DiffResult{Changes: plugin.DiffNone}, diff)
 
 		// The original provider should be used because the config did not change.
 		p2, ok := r.GetProvider(Reference{urn: urn, id: id})