libs/pubsub/query: specify peg version in go.mod (#9099)

* libs/pubsub/query: specify peg version in go.mod

The code to generate the pubsub queries was dependent on an unspecified
version of the peg tool. This brings peg into go.mod so it is on a fixed
version. This should also enable dependabot to notify us of future
updates to peg.

The version of query.peg.go generated from the current version of peg
correctly contains the special "Code generated by..." line to indicate
to other tools that the file is automatically generated and should
therefore be excluded from linters, etc.

I removed the make target as there were no git grep results referencing
"gen_query_parser"; directly running "go generate" is a reasonable
expectation in Go projects.

Now that "go run" is module aware, I would typically use "go run" inside
the go:generate directive, but in this case we go build to a gitignore-d
directory in order to work around the nondeterministic output detailed
in pointlander/peg#129.

* libs/pubsub/query: check error from (*QueryParser).Init()

The newly generated peg code returns an error from Init(); the previous
version was niladic.

Co-authored-by: Sam Kleinman <garen@tychoish.com>

libs/pubsub/query/.gitignore

@@ -0,0 +1,7 @@
+# This is a temporary directory to hold the peg binary,
+# to work around https://github.com/pointlander/peg/issues/129.
+# Note that once we have a new version of peg fixing #129,
+# we may still want to keep this .gitignore to prevent anyone
+# from accidentally running "git add ." and including their built
+# peg binary in a commit.
+.bin/

libs/pubsub/query/Makefile

@@ -1,11 +1,7 @@
-gen_query_parser:
-	go get -u -v github.com/pointlander/peg
-	peg -inline -switch query.peg
-
 fuzzy_test:
 	go get -u -v github.com/dvyukov/go-fuzz/go-fuzz
 	go get -u -v github.com/dvyukov/go-fuzz/go-fuzz-build
 	go-fuzz-build github.com/tendermint/tendermint/libs/pubsub/query/fuzz_test
 	go-fuzz -bin=./fuzz_test-fuzz.zip -workdir=./fuzz_test/output
 
-.PHONY: gen_query_parser fuzzy_test
+.PHONY: fuzzy_test

libs/pubsub/query/peg.go

@@ -1,3 +1,10 @@
 package query
 
-//go:generate peg -inline -switch query.peg
+// Normally I would use go run,
+// but the "Code generated by" comment for peg includes the full arg0,
+// which includes an unpredictable temporary directory,
+// resulting in a nondeterminstic generated source file.
+// Using go build is the workaround as detailed in https://github.com/pointlander/peg/issues/129.
+
+//go:generate go build -o ./.bin/peg github.com/pointlander/peg
+//go:generate ./.bin/peg -inline -switch query.peg

libs/pubsub/query/query.go

@@ -39,7 +39,9 @@ type Condition struct {
 // invalid.
 func New(s string) (*Query, error) {
 	p := &QueryParser{Buffer: fmt.Sprintf(`"%s"`, s)}
-	p.Init()
+	if err := p.Init(); err != nil {
+		return nil, err
+	}
 	if err := p.Parse(); err != nil {
 		return nil, err
 	}
@@ -101,7 +103,7 @@ func (q *Query) Conditions() ([]Condition, error) {
 	buffer, begin, end := q.parser.Buffer, 0, 0
 
 	// tokens must be in the following order: tag ("tx.gas") -> operator ("=") -> operand ("7")
-	for token := range q.parser.Tokens() {
+	for _, token := range q.parser.Tokens() {
 		switch token.pegRule {
 		case rulePegText:
 			begin, end = int(token.begin), int(token.end)
@@ -213,7 +215,7 @@ func (q *Query) Matches(events map[string][]string) (bool, error) {
 	// tokens must be in the following order:
 
 	// tag ("tx.gas") -> operator ("=") -> operand ("7")
-	for token := range q.parser.Tokens() {
+	for _, token := range q.parser.Tokens() {
 		switch token.pegRule {
 		case rulePegText:
 			begin, end = int(token.begin), int(token.end)