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feat(cel): Add CEL custom library for semver comparison (#202)
* feat(cel): Add CEL custom library for semver comparison Add CEL custom library for semver comparison to api repo. This library is used in olm and registry. Signed-off-by: Vu Dinh <vudinh@outlook.com> * Simplify the CEL library code structure Remind the original cel package to constraints pkg to reflect that there will be more type of constraints. Remove the evaluator/provider interfaces that are not needed yet. The generic interface can be designed later when a new type of constraint is introduced. Signed-off-by: Vu Dinh <vudinh@outlook.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,146 @@ | ||
| package constraints | ||
|
|
||
| import ( | ||
| "fmt" | ||
|
|
||
| "github.com/google/cel-go/cel" | ||
| "github.com/google/cel-go/checker/decls" | ||
| "github.com/google/cel-go/common/types" | ||
| "github.com/google/cel-go/common/types/ref" | ||
| "github.com/google/cel-go/interpreter/functions" | ||
| exprpb "google.golang.org/genproto/googleapis/api/expr/v1alpha1" | ||
|
|
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| "github.com/blang/semver/v4" | ||
| ) | ||
|
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| // PropertiesKey is the key for bundle properties map (input data for CEL evaluation) | ||
| const PropertiesKey = "properties" | ||
|
|
||
| // Constraint is a struct representing the new generic constraint type | ||
| type Constraint struct { | ||
| // Constraint message that surfaces in resolution | ||
| // This field is optional | ||
| Message string `json:"message" yaml:"message"` | ||
|
|
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| // The cel struct that contraints CEL expression | ||
| // This field is required | ||
| Cel *Cel `json:"cel" yaml:"cel"` | ||
| } | ||
|
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| // Cel is a struct representing CEL expression information | ||
| type Cel struct { | ||
| // The CEL expression | ||
| Rule string `json:"rule" yaml:"rule"` | ||
| } | ||
|
|
||
| // NewCelEnvironment returns a CEL environment which can be used to | ||
| // evaluate CEL expression and an error if occurs | ||
| func NewCelEnvironment() *CelEnvironment { | ||
| env, err := cel.NewEnv(cel.Declarations( | ||
| decls.NewVar(PropertiesKey, decls.NewListType(decls.NewMapType(decls.String, decls.Any)))), | ||
| cel.Lib(semverLib{}), | ||
| ) | ||
| // If an error occurs here, it means the CEL enviroment is unable to load | ||
| // configuration for custom libraries propertly. Hence, the CEL enviroment is | ||
| // unusable. Panic here will cause the program to fail immediately to prevent | ||
| // cascading failures later on when this CEL env is in use. | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
| return &CelEnvironment{ | ||
| env: env, | ||
| } | ||
| } | ||
|
|
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| // CelEnvironment is a struct that encapsulates CEL custom program enviroment | ||
| type CelEnvironment struct { | ||
| env *cel.Env | ||
| } | ||
|
|
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| // CelProgram is a struct that encapsulates compiled CEL program | ||
| type CelProgram struct { | ||
| program cel.Program | ||
| } | ||
|
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| /* | ||
| This section of code is for custom library for semver comparison in CEL | ||
| The code is inspired by https://github.com/google/cel-go/blob/master/cel/cel_test.go#L46 | ||
| The semver_compare is written based on `Compare` function in https://github.com/blang/semver | ||
| particularly in https://github.com/blang/semver/blob/master/semver.go#L125 | ||
| Example: | ||
| `semver_compare(v1, v2)` is equivalent of `v1.Compare(v2)` in blang/semver library | ||
| The result is `semver_compare` is an integer just like `Compare`. So, the CEL | ||
| expression `semver_compare(v1, v2) == 0` is equivalent v1.Compare(v2) == 0. In | ||
| the other words, it checks if v1 is equal to v2 in term of semver comparision. | ||
| */ | ||
| type semverLib struct{} | ||
|
|
||
| func (semverLib) CompileOptions() []cel.EnvOption { | ||
| return []cel.EnvOption{ | ||
| cel.Declarations( | ||
| decls.NewFunction("semver_compare", | ||
| decls.NewOverload("semver_compare", | ||
| []*exprpb.Type{decls.Any, decls.Any}, | ||
| decls.Int))), | ||
| } | ||
| } | ||
|
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| func (semverLib) ProgramOptions() []cel.ProgramOption { | ||
| return []cel.ProgramOption{ | ||
| cel.Functions( | ||
| &functions.Overload{ | ||
| Operator: "semver_compare", | ||
| Binary: semverCompare, | ||
| }, | ||
| ), | ||
| } | ||
| } | ||
|
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| func semverCompare(val1, val2 ref.Val) ref.Val { | ||
| v1, err := semver.ParseTolerant(fmt.Sprint(val1.Value())) | ||
| if err != nil { | ||
| return types.ValOrErr(val1, "unable to parse '%v' to semver format", val1.Value()) | ||
| } | ||
|
|
||
| v2, err := semver.ParseTolerant(fmt.Sprint(val2.Value())) | ||
| if err != nil { | ||
| return types.ValOrErr(val2, "unable to parse '%v' to semver format", val2.Value()) | ||
| } | ||
| return types.Int(v1.Compare(v2)) | ||
| } | ||
|
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| // Evaluate to evaluate the compiled CEL program against input data (map) | ||
| func (e CelProgram) Evaluate(data map[string]interface{}) (bool, error) { | ||
| result, _, err := e.program.Eval(data) | ||
| if err != nil { | ||
| return false, err | ||
| } | ||
|
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| // we should have already ensured that this will be types.Bool during compilation | ||
| if b, ok := result.Value().(bool); ok { | ||
| return b, nil | ||
| } | ||
| return false, fmt.Errorf("cel expression evalutated to %T, not bool", result.Value()) | ||
| } | ||
|
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| // Validate to validate the CEL expression string by compiling it into CEL program | ||
| func (e *CelEnvironment) Validate(rule string) (CelProgram, error) { | ||
| var celProg CelProgram | ||
| ast, issues := e.env.Compile(rule) | ||
| if err := issues.Err(); err != nil { | ||
| return celProg, err | ||
| } | ||
|
|
||
| if ast.ResultType() != decls.Bool { | ||
| return celProg, fmt.Errorf("cel expressions must have type Bool") | ||
| } | ||
|
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| prog, err := e.env.Program(ast) | ||
| if err != nil { | ||
| return celProg, err | ||
| } | ||
| return CelProgram{program: prog}, nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,71 @@ | ||
| package constraints | ||
|
|
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| import ( | ||
| "testing" | ||
|
|
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| "github.com/stretchr/testify/assert" | ||
| ) | ||
|
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| func TestCelLibrary(t *testing.T) { | ||
| props := make([]map[string]interface{}, 1) | ||
| props[0] = map[string]interface{}{ | ||
| "type": "olm.test", | ||
| "value": "1.0.0", | ||
| } | ||
|
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| propertiesMap := map[string]interface{}{"properties": props} | ||
|
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| tests := []struct { | ||
| name string | ||
| rule string | ||
| out bool | ||
| isErr bool | ||
| }{ | ||
| { | ||
| name: "ValidCelExpression/True", | ||
| rule: "properties.exists(p, p.type == 'olm.test' && (semver_compare(p.value, '1.0.0') == 0))", | ||
| out: true, | ||
| isErr: false, | ||
| }, | ||
| { | ||
| name: "ValidCelExpression/NotEqual/False", | ||
| rule: "properties.exists(p, p.type == 'olm.test' && (semver_compare(p.value, '1.0.1') == 0))", | ||
| out: false, | ||
| isErr: false, | ||
| }, | ||
| { | ||
| name: "ValidCelExpression/Less/False", | ||
| rule: "properties.exists(p, p.type == 'olm.test' && (semver_compare(p.value, '1.0.0') < 0))", | ||
| isErr: false, | ||
| }, | ||
| { | ||
| name: "ValidCelExpression/Larger/False", | ||
| rule: "properties.exists(p, p.type == 'olm.test' && (semver_compare(p.value, '1.0.0') > 0))", | ||
| isErr: false, | ||
| }, | ||
| { | ||
| name: "InvalidCelExpression/NotExistedFunc", | ||
| rule: "properties.exists(p, p.type == 'olm.test' && (doesnt_exist(p.value, '1.0.0') == 0))", | ||
| isErr: true, | ||
| }, | ||
| { | ||
| name: "InvalidCelExpression/NonBoolReturn", | ||
| rule: "1", | ||
| isErr: true, | ||
| }, | ||
| } | ||
|
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| validator := NewCelEnvironment() | ||
| for _, tt := range tests { | ||
| t.Run(tt.name, func(t *testing.T) { | ||
| prog, err := validator.Validate(tt.rule) | ||
| if tt.isErr { | ||
| assert.Error(t, err) | ||
| } else { | ||
| result, err := prog.Evaluate(propertiesMap) | ||
| assert.NoError(t, err) | ||
| assert.Equal(t, result, tt.out) | ||
| } | ||
| }) | ||
| } | ||
| } |
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