Display error when multiple mutation blocks

[srfrog]

This PR adds a check that there's only a single mutation block per request, otherwise an error is returned.

Closes #2815

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This change is 

[manishrjain]

Reviewable status: 0 of 2 files reviewed, 2 unresolved discussions (waiting on @srfrog and @manishrjain)

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gql/parser_mutation.go, line 50 at r1 (raw file):

		if item.Typ == itemRightCurl {
			// mutations must be enclosed in a single block.
			if it.Next() && it.Item().Typ == itemLeftCurl {

We should check for itemEOF instead.

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gql/parser_test.go, line 4296 at r1 (raw file):

func TestParseMutationTooManyBlocks(t *testing.T) {
	m := `{
		set { _:a1 <reg>  "a1 content" . }

Can you add a test case like this:

{ set { ...}} something

[srfrog]

Reviewable status: 0 of 2 files reviewed, 2 unresolved discussions (waiting on @manishrjain)

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gql/parser_mutation.go, line 50 at r1 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

We should check for itemEOF instead.

Done.

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gql/parser_test.go, line 4296 at r1 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

Can you add a test case like this:

{ set { ...}} something

Also added a case for comments

[srfrog]

Reviewable status: 0 of 2 files reviewed, 2 unresolved discussions (waiting on @manishrjain)

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gql/parser_test.go, line 4296 at r1 (raw file):

Previously, srfrog (Gus) wrote…

Also added a case for comments

Done.

[manishrjain]

Reviewable status: 0 of 2 files reviewed, 2 unresolved discussions (waiting on @srfrog)

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gql/parser_mutation.go, line 27 at r2 (raw file):

)

var ErrMutationTooManyBlocks = errors.New("Too many mutation blocks.")

Don't make a generic error. See below.

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gql/parser_mutation.go, line 51 at r2 (raw file):

			// mutations must be enclosed in a single block.
			if it.Next() && it.Item().Typ != lex.ItemEOF {
				return nil, ErrMutationTooManyBlocks

We can return a very specific error message here, which would be useful for the user. Like the text which we found here.

In general, I think lexer can do a better job of tracking the line and the column number of the item. And then display that in error messages, so users know exactly where their errors are. All of these errors in parsers need to be improved.

[srfrog]

Reviewable status: 0 of 2 files reviewed, 2 unresolved discussions (waiting on @manishrjain)

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gql/parser_mutation.go, line 27 at r2 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

Don't make a generic error. See below.

Done.

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gql/parser_mutation.go, line 51 at r2 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

We can return a very specific error message here, which would be useful for the user. Like the text which we found here.

In general, I think lexer can do a better job of tracking the line and the column number of the item. And then display that in error messages, so users know exactly where their errors are. All of these errors in parsers need to be improved.

I've added some context to the error. I will add line support in the parser in another issue.

[manishrjain]

Reviewed 2 of 2 files at r3.
Reviewable status: complete! all files reviewed, all discussions resolved