Working implementation of visitor and printer

[sogko]

Built upon PR #8

Details

visitor

• visitor is used / will be used by printer and validator
• Ported from graphql-js visit()
• Walks through an AST using a depth first traversal, calling visitor's Enter function when entering a node and visitor's Leave function when leaving a node
• Visitor's functions
  • type VisitFunc func(p VisitFuncParams) (action string, result interface{})
  • The value of returned action string defines the behaviour of the visit function upon return
    • const visitor.ActionNoChange
      • No changes to node, regardless of result interface{} returned
    • const visitor.ActionBreak
      • Stop traversal of tree, ignore result interface{} returned
    • const visitor.ActionSkip
      • Skip traversal of sub-tree, ignore result interface{} returned
    • const visitor.ActionUpdate
      • Update the value of current node with value of returned result interface{}. Return result = nil to remove node.
• See printer's printDocASTReducer for working usage of visitor

printer

• printer is used to transform/reduce an ast.Node into a string.
• Uses visitor and pre-defined visitor.VisitorOptions to traverse AST and reduce each node to a string (printDocASTReducer)
• Inverse of parser (which transforms string into an ast.Node)

// pseudo-code
query := `{ field }`
astDoc := parse(query)
printed := print(astDoc)
assert(query == printed)

Misc

• Added language/parser/schema_parser_test.go test to complete port of all graphql-js/language/__tests__/* tests

Test

$ go build && go test ./...
ok      github.com/chris-ramon/graphql-go   0.027s
?       github.com/chris-ramon/graphql-go/errors    [no test files]
ok      github.com/chris-ramon/graphql-go/executor  0.097s
?       github.com/chris-ramon/graphql-go/language/ast  [no test files]
?       github.com/chris-ramon/graphql-go/language/kinds    [no test files]
ok      github.com/chris-ramon/graphql-go/language/lexer    0.017s
?       github.com/chris-ramon/graphql-go/language/location [no test files]
ok      github.com/chris-ramon/graphql-go/language/parser   0.034s
ok      github.com/chris-ramon/graphql-go/language/printer  0.042s
?       github.com/chris-ramon/graphql-go/language/source   [no test files]
ok      github.com/chris-ramon/graphql-go/language/visitor  0.016s
?       github.com/chris-ramon/graphql-go/testutil  [no test files]
ok      github.com/chris-ramon/graphql-go/types 0.018s
?       github.com/chris-ramon/graphql-go/validator [no test files]

[chris-ramon]

Amazing @sogko!, I am so glad for ur great work, I am continue reviewing the previos pr, looking very good so far, as soon as I am done reviewing I will comment on it, then next I will reviewing this one.

Again thanks for ur amazing work on this lib 🌟.

[sogko]

Thanks for even taking the time to look into this 👍🏻

If you want to feel more comfortable and make some changes to my PRs directly, you can create a separate branch (develop branch for e.g.) and I can re-submit the PRs into that instead of the master branch.

You can then mess around with it without worrying about committing too much to my PRs.

And once you feel comfortable with the state of the develop branch, you can safely merge it back to master for public use.

[chris-ramon]

Thanks for feedback @sogko 👍 , I think we should keep going forward to merging directly to master.

We have good quantity of test covering lib which give us enough confidence to do so, besides that I am going to add converge with coveralls.io so I think we are fine.