CUE: a data constraint language and shoo-in for Go – Marcel van Lohuizen

Transcript

1. CUE: a data constraint language and shoo-in for Go @mpvl_ Google, Go team https://cue.googlesource.com/cue https://github.com/cuelang/cue
2. Image source: Wikimedia Commons. Google Mountain View campus dinosaur skeleton 'Stan' CC-SA 3.0 images Background
3. Image source: Pixabay. View of Street from a Glass Window CC images What could be done better?
4. Poor or no validation !4
5. Inheritance is the biggest source of complexity in configuration languages !5
6. WHAT WERE THESE LINGUISTS DOING AGAIN? !6 graph unification
7. ESSENTIAL PROPERTIES !7 A & A ≡ A A & B ≡ B & A (A & B) & C ≡ A & (B & C) Associative Commutative Idempotent
8. CUE CONCEPTS Types
 are
 Values !8
9. TYPES ARE VALUES !9 moscow: {
 name: "Moscow"
 pop: 11.92M
 capital: true
 } JSON equivalent in CUE "moscow": {
 "name": "Moscow",
 "pop": 11920000,
 "capital": true
 }
10. TYPES ARE VALUES !10 municipality: {
 name: string
 pop: int
 capital: bool
 } Go struct equivalent in CUE type Municipality struct { Name string
 Pop int
 Capital bool
 }
11. TYPES ARE VALUES !11 largeCapital: {
 name: string
 pop: >5M
 capital: true
 } CUE allows anything in between
12. CUE CONCEPTS Lattice of Values !12 Image source: I, KSmrq, Hasse diagram, powerset of {x,y,z} ordered by inclusion. CC BY-SA 3.0
13. VALUE LATTICE !13 largeCapital: {
 name: string
 pop: >5M
 capital: true
 } municipality: {
 name: string
 pop: int
 capital: bool
 } moscow: {
 name: "Moscow"
 pop: 11.92M
 capital: true
 } Value (JSON) Type (Go struct) Mixed (CUE) more specific
14. VALUE LATTICE !14 number <5 >3 1 4 _|_ _ string >3 & <5 =~ "^[a-z]{3}$" > "e" "bar" "foo" "foobar" 8 more specific
15. VALUE LATTICE inheritance, overrides !15 1 == 1
16. NO INHERITANCE? Constraints used for validation and 
 reducing boilerplate !16
17. OTHER HIGHLIGHTS • Path shorthand: a: { b: { c: 5 }}} == a b c: 5 • References • Sum types/enums a | b | c • Default values number | *1 • Arithmetic 4 + 5 • String interpolation "Hello \(person)" • List and field comprehensions [ x for x in y ] !17
18. Image source: Ron Berg Pixabay Licence Practice
19. Defining Schema is cumbersome, keeping them in sync much worse! !19
20. ENTER THE GOPHER !20 Gopher by Renée French • CUE is JSON superset + Go's encoding/json = Profit
21. DEMO TIME !21 Go code Master Pod CUE from Go CUE From User Go code cue get go cue cmd CUE scripting YAML Verified CUE kubectl create
22. Demo
23. Associate constraints using struct field tags type Sum struct { A int `cue:"C-B" json:",omitempty"` B int `cue:"C-A" json:",omitempty"` C int `cue:"A+B" json:",omitempty"` } Go struct with cue field tags a := Sum{A: 1, B: 5, C: 10} err := cuego.Complete(&a)
 fmt.Printf(err==nil) // false a = Sum{A: 1, B: 5} err = cuego.Complete(&a)
 fmt.Printf("%#v\n", a) // Sum{A:1, B:5, C:6} Example: cuego.Complete
24. cuelang.org/cue/go/cuego.Validate type Setup struct { FileName string Min, Max int } func init() { cuego.MustAddConstraints(&Setup{}, `{ Filename: =~".json$" // must be a .json file Min: >100 & <=Max Max: <=10_000 }`) } Associate Go type with CUE fmt.Println( cuego.Validate(&Config{"foo.jso", 120, 500})) // "foo.jso" does not match =~".json$" Usage cuego.Validate
25. TODOS • Protobuf, OpenAPI, ... • Diffing functionality • Testing facilities • Auto-derive templates • Extend scripting layer !25
26. CUE&A @mpvl_ https://cue.googlesource.com/cue https://github.com/cuelang/cue (mirror) !26 CUE