From 151c98f27c86e1ccfe04f7074d7204cd17e207e7 Mon Sep 17 00:00:00 2001 From: Jason Hall Date: Thu, 11 Jun 2020 20:13:49 -0400 Subject: [PATCH] initial commit --- README.md | 48 ++++++++++++++++++++++++++++++++++++++ condition.yaml | 11 +++++++++ go.mod | 5 ++++ go.sum | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++ main.go | 39 +++++++++++++++++++++++++++++++ 5 files changed, 165 insertions(+) create mode 100644 README.md create mode 100644 condition.yaml create mode 100644 go.mod create mode 100644 go.sum create mode 100644 main.go diff --git a/README.md b/README.md new file mode 100644 index 0000000..564e199 --- /dev/null +++ b/README.md @@ -0,0 +1,48 @@ +# `cel` Condition + +This Tekton `Condition` can be used in a Pipeline to gate execution of a `Task` +on the successful evaluation and result of a CEL expression, passed as an argument. + +## Usage + +Install the Condition: + +``` +KO_DOCKER_REPO=gcr.io/ ko apply -f condition.yaml +``` + +Use the Condition in a Pipeline: + +``` +apiVersion: tekton.dev/v1alpha1 +kind: Pipeline +metadata: + name: say-hello-if-300-is-even +spec: + tasks: + - name: say-hello + conditions: + - conditionRef: 'cel' + params: + - name: expression + value: '300 % 2 == 0' + taskSpec: + steps: + - image: busybox + script: echo hello +``` + +When the Pipeline is run, the Task will only run and echo `hello` if the number +300 is even (which it always is). + +## Limitations + +* There are no custom methods provided. Some could be added in the future. + +* At this time, the expression must be fully specified upfront, and can't + reference any other Pipeline parameters (i.e., `expression`'s value can't be + dependent on the resolved value of another parameter). This limits its + usefulness. + +* Tekton will spawn a Pod just to evaluate the expression, when it's perfectly + safe to evaluate the expression in the control plane. diff --git a/condition.yaml b/condition.yaml new file mode 100644 index 0000000..bb2a5c0 --- /dev/null +++ b/condition.yaml @@ -0,0 +1,11 @@ +apiVersion: tekton.dev/v1alpha1 +kind: Condition +metadata: + name: cel +spec: + parameters: + - name: expression + default: 'true' + check: + image: ko://github.com/imjasonh/cel-condition + args: ['$(params.expression)'] diff --git a/go.mod b/go.mod new file mode 100644 index 0000000..a11635c --- /dev/null +++ b/go.mod @@ -0,0 +1,5 @@ +module github.com/imjasonh/cel-condition + +go 1.14 + +require github.com/google/cel-go v0.5.1 diff --git a/go.sum b/go.sum new file mode 100644 index 0000000..5f6a474 --- /dev/null +++ b/go.sum @@ -0,0 +1,62 @@ +cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw= +github.com/BurntSushi/toml v0.3.1/go.mod 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+google.golang.org/grpc v1.27.1/go.mod h1:qbnxyOmOxrQa7FizSgH+ReBfzJrCY1pSN7KXBS8abTk= +honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4= +honnef.co/go/tools v0.0.0-20190523083050-ea95bdfd59fc/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4= diff --git a/main.go b/main.go new file mode 100644 index 0000000..e589ff5 --- /dev/null +++ b/main.go @@ -0,0 +1,39 @@ +package main + +import ( + "log" + "os" + + "github.com/google/cel-go/cel" + "github.com/google/cel-go/common/types" +) + +func main() { + e := os.Args[1] + log.Printf("evaluating %q", e) + + env, err := cel.NewEnv(cel.Declarations()) + if err != nil { + log.Fatalln(err) + } + ast, iss := env.Compile(e) + if iss.Err() != nil { + // Syntax error. + log.Fatalln(iss.Err()) + } + + prg, err := env.Program(ast) + out, _, err := prg.Eval(map[string]interface{}{}) + if err != nil { + // Error evaluating. + log.Fatalln(err) + } + + if !types.IsBool(out) { + log.Fatalf("result (%v) is not boolean (type: %s)", out.Value(), out.Type().TypeName()) + } + if out != types.Bool(true) { + log.Fatal("result is false") + } + log.Println("result is true") +}