Remote Resolution Refactor

This PR implements an updated resolver framework with slight updates. This is to avoid backwards incompatibility while implementing [TEP-0154](tektoncd/community#1138).

The current framework only works with Params. e.g. The interface has ValidateParams and Resolve which takes in Params. Now that we also need to pass in a `URL`, we need to add new methods and change function signatures which leads to API incompatibility with existing custom resolvers. As a result, when users upgrade to new version of Tekton Pipelines, they will be forced to be compatible with the new format because of the interface changes.

This PR tries to make it future proof such that if we add new fields to the ResolutionSpec, it will be handled without the need to break users.

cmd/resolvers/main.go

@@ -21,12 +21,12 @@ import (
 	"strings"
 
 	"github.com/tektoncd/pipeline/pkg/apis/resolution/v1alpha1"
-	"github.com/tektoncd/pipeline/pkg/resolution/resolver/bundle"
-	"github.com/tektoncd/pipeline/pkg/resolution/resolver/cluster"
-	"github.com/tektoncd/pipeline/pkg/resolution/resolver/framework"
-	"github.com/tektoncd/pipeline/pkg/resolution/resolver/git"
-	"github.com/tektoncd/pipeline/pkg/resolution/resolver/http"
-	"github.com/tektoncd/pipeline/pkg/resolution/resolver/hub"
+	"github.com/tektoncd/pipeline/pkg/resolution/v2/resolver/bundle"
+	"github.com/tektoncd/pipeline/pkg/resolution/v2/resolver/cluster"
+	"github.com/tektoncd/pipeline/pkg/resolution/v2/resolver/framework"
+	"github.com/tektoncd/pipeline/pkg/resolution/v2/resolver/git"
+	"github.com/tektoncd/pipeline/pkg/resolution/v2/resolver/http"
+	"github.com/tektoncd/pipeline/pkg/resolution/v2/resolver/hub"
 	filteredinformerfactory "knative.dev/pkg/client/injection/kube/informers/factory/filtered"
 	"knative.dev/pkg/injection/sharedmain"
 	"knative.dev/pkg/signals"

docs/how-to-write-a-resolver.md

@@ -7,6 +7,8 @@ weight: 104
 
 # How to write a Resolver
 
+**Note**: [Here](#old-resolver-framework/how-to-write-a-resolver.md) is the older version of the framework.
+
 This how-to will outline the steps a developer needs to take when creating
 a new (very basic) Resolver. Rather than focus on support for a particular version
 control system or cloud platform this Resolver will simply respond with
@@ -102,7 +104,7 @@ package main
 
 import (
   "context"
-  "github.com/tektoncd/pipeline/pkg/resolution/resolver/framework"
+  "github.com/tektoncd/pipeline/pkg/resolution/v2/resolver/framework"
   "knative.dev/pkg/injection/sharedmain"
 )
 
@@ -137,7 +139,7 @@ type framework.Resolver in argument to framework.NewController:
 
 We've already defined our own `resolver` type but in order to get the
 resolver running you'll need to add the methods defined in [the
-`framework.Resolver` interface](../pkg/resolution/resolver/framework/interface.go)
+`framework.Resolver` interface](../pkg/resolution/v2/resolver/framework/interface.go)
 to your `main.go` file. Going through each method in turn:
 
 ## The `Initialize` method
@@ -194,23 +196,23 @@ import (
   "context"
 
   // Add this one; it defines LabelKeyResolverType we use in GetSelector
-  "github.com/tektoncd/pipeline/pkg/resolution/common"
-  "github.com/tektoncd/pipeline/pkg/resolution/resolver/framework"
+  "github.com/tektoncd/pipeline/pkg/resolution/v2/common"
+  "github.com/tektoncd/pipeline/pkg/resolution/v2/resolver/framework"
   "knative.dev/pkg/injection/sharedmain"
   pipelinev1 "github.com/tektoncd/pipeline/pkg/apis/pipeline/v1"
 )
 ```
 
-## The `ValidateParams` method
+## The `Validate` method
 
-The `ValidateParams` method checks that the params submitted as part of
+The `Validate` method checks that the resolution-spec submitted as part of
 a resolution request are valid. Our example resolver doesn't expect
-any params so we'll simply ensure that the given map is empty.
+any params in the spec so we'll simply ensure that the there are no params.
 
 ```go
-// ValidateParams ensures parameters from a request are as expected.
-func (r *resolver) ValidateParams(ctx context.Context, params map[string]string) error {
-  if len(params) > 0 {
+// Validate ensures that the resolution spec from a request is as expected.
+func (r *resolver) Validate(ctx context.Context, req *v1beta1.ResolutionRequestSpec) error {
+  if len(req.Params) > 0 {
     return errors.New("no params allowed")
   }
   return nil
@@ -233,8 +235,8 @@ The method signature we're implementing here has a
 is another type we have to implement but it has a small footprint:
 
 ```go
-// Resolve uses the given params to resolve the requested file or resource.
-func (r *resolver) Resolve(ctx context.Context, params map[string]string) (framework.ResolvedResource, error) {
+// Resolve uses the given resolution spec to resolve the requested file or resource.
+func (r *resolver) Resolve(ctx context.Context, req *v1beta1.ResolutionRequestSpec) (framework.ResolvedResource, error) {
   return &myResolvedResource{}, nil
 }
 
@@ -450,7 +452,7 @@ Resolver to fetch data from your storage backend of choice.
 
 Or if you prefer to take a look at a more fully-realized example of a
 Resolver, see the [code for the `gitresolver` hosted in the Tekton
-Pipeline repo](https://github.com/tektoncd/pipeline/tree/main/pkg/resolution/resolver/git/).
+Pipeline repo](https://github.com/tektoncd/pipeline/tree/main/pkg/resolution/v2/resolver/git/).
 
 Finally, another direction you could take this would be to try writing a
 `PipelineRun` for Tekton Pipelines that speaks to your Resolver. Can