selector: add tests which are driven by language-agnostic spec fixtures.

.gitmodules

@@ -0,0 +1,3 @@
+[submodule ".ipld"]
+	path = .ipld
+	url = https://github.com/ipld/ipld/

go.mod

@@ -8,5 +8,6 @@ require (
 	github.com/multiformats/go-multihash v0.0.15
 	github.com/polydawn/refmt v0.0.0-20201211092308-30ac6d18308e
 	github.com/smartystreets/goconvey v1.6.4 // indirect
+	github.com/warpfork/go-testmark v0.3.0
 	github.com/warpfork/go-wish v0.0.0-20200122115046-b9ea61034e4a
 )

go.sum

@@ -40,6 +40,8 @@ github.com/smartystreets/assertions v0.0.0-20180927180507-b2de0cb4f26d/go.mod h1
 github.com/smartystreets/goconvey v1.6.4 h1:fv0U8FUIMPNf1L9lnHLvLhgicrIVChEkdzIKYqbNC9s=
 github.com/smartystreets/goconvey v1.6.4/go.mod h1:syvi0/a8iFYH4r/RixwvyeAJjdLS9QV7WQ/tjFTllLA=
 github.com/spaolacci/murmur3 v1.1.0/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
+github.com/warpfork/go-testmark v0.3.0 h1:Q81c4u7hT+BR5kNfNQhEF0VT2pmL7+Kk0wD+ORYl7iA=
+github.com/warpfork/go-testmark v0.3.0/go.mod h1:jhEf8FVxd+F17juRubpmut64NEG6I2rgkUhlcqqXwE0=
 github.com/warpfork/go-wish v0.0.0-20200122115046-b9ea61034e4a h1:G++j5e0OC488te356JvdhaM8YS6nMsjLAYF7JxCv07w=
 github.com/warpfork/go-wish v0.0.0-20200122115046-b9ea61034e4a/go.mod h1:x6AKhvSSexNrVSrViXSHUEbICjmGXhtgABaHIySUSGw=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=

traversal/selector/spec_test.go

@@ -0,0 +1,112 @@
+package selector_test
+
+import (
+	"bytes"
+	"os"
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+	"github.com/warpfork/go-testmark"
+
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/codec/dagjson"
+	"github.com/ipld/go-ipld-prime/codec/json"
+	"github.com/ipld/go-ipld-prime/fluent/qp"
+	"github.com/ipld/go-ipld-prime/node/basic"
+	"github.com/ipld/go-ipld-prime/traversal"
+	"github.com/ipld/go-ipld-prime/traversal/selector/parse"
+)
+
+func TestSpecFixtures(t *testing.T) {
+	doc, err := testmark.ReadFile("../../.ipld/specs/selectors/fixtures/selector-fixtures-1.md")
+	if os.IsNotExist(err) {
+		t.Skipf("not running spec suite: %s (did you clone the submodule with the data?)", err)
+	}
+	if err != nil {
+		t.Fatalf("spec file parse failed?!: %s", err)
+	}
+
+	// Data hunk in this spec file are in "directories" of a test scenario each.
+	doc.BuildDirIndex()
+	for _, dir := range doc.DirEnt.ChildrenList {
+		t.Run(dir.Name, func(t *testing.T) {
+			// Each "directory" contains three piece of data:
+			//  - `data` -- this is the "block". It's arbitrary example data. They're all in json (or dag-json) format, for simplicity.
+			//  - `selector` -- this is the selector. Again, as json.
+			//  - `expect-visit` -- these are json lines (one json object on each line) containing description of each node that should be visited, in order.
+			fixtureData := dir.Children["data"].Hunk.Body
+			fixtureSelector := dir.Children["selector"].Hunk.Body
+			fixtureExpect := dir.Children["expect-visit"].Hunk.Body
+
+			// Parse data into DMT form.
+			nb := basicnode.Prototype.Any.NewBuilder()
+			if err := dagjson.Decode(nb, bytes.NewReader(fixtureData)); err != nil {
+				t.Errorf("failed to parse fixture data: %s", err)
+			}
+			dataDmt := nb.Build()
+
+			// Parse and compile Selector.
+			// (This is already arguably a test event on its own.
+			selector, err := selectorparse.ParseAndCompileJSONSelector(string(fixtureSelector))
+			if err != nil {
+				t.Errorf("failed to parse+compile selector: %s", err)
+			}
+
+			// Go!
+			//  We'll store the logs of our visit events as... ipld Nodes, actually.
+			//  This will make them easy to serialize, which is good for two reasons:
+			//   at the end, we're actually going to... do that, and use string diffs for the final assertion
+			//    (because string diffing is actually really nice for aggregate feedback in a system like this);
+			//   and also that means we're ready to save updated serial data into the fixture files, if we did want to patch them.
+			var visitLogs []ipld.Node
+			traversal.WalkAdv(dataDmt, selector, func(prog traversal.Progress, n ipld.Node, reason traversal.VisitReason) error {
+				// Munge info about where we are into DMT shaped like the expectation records in the fixture.
+				visitEventDescr, err := qp.BuildMap(basicnode.Prototype.Any, 3, func(ma ipld.MapAssembler) {
+					qp.MapEntry(ma, "path", qp.String(prog.Path.String()))
+					qp.MapEntry(ma, "node", qp.Map(1, func(ma ipld.MapAssembler) {
+						qp.MapEntry(ma, n.Kind().String(), func(na ipld.NodeAssembler) {
+							switch n.Kind() {
+							case ipld.Kind_Map, ipld.Kind_List:
+								na.AssignNull()
+							default:
+								na.AssignNode(n)
+							}
+						})
+					}))
+					qp.MapEntry(ma, "matched", qp.Bool(reason == traversal.VisitReason_SelectionMatch))
+				})
+				if err != nil {
+					panic("insanity at a deeper level than this test's target")
+				}
+				visitLogs = append(visitLogs, visitEventDescr)
+				return nil
+			})
+
+			// Brief detour -- we're going to bounce the fixture data through our own deserialize and serialize.
+			//  Just to normalize the heck out of it.  I'm not really interested in if the fixture files have non-normative whitespace in them.
+			var fixtureExpectNormBuf bytes.Buffer
+			for _, line := range bytes.Split(fixtureExpect, []byte{'\n'}) {
+				if len(line) == 0 {
+					continue
+				}
+				nb := basicnode.Prototype.Any.NewBuilder()
+				if err := json.Decode(nb, bytes.NewReader(line)); err != nil {
+					t.Errorf("failed to parse fixture visit descriptions: %s", err)
+				}
+				json.Encode(nb.Build(), &fixtureExpectNormBuf)
+				fixtureExpectNormBuf.WriteByte('\n')
+			}
+
+			// Serialize our own visit logs now too.
+			var visitLogString bytes.Buffer
+			for _, logEnt := range visitLogs {
+				json.Encode(logEnt, &visitLogString)
+				visitLogString.WriteByte('\n')
+			}
+
+			// DIFF TIME.
+			qt.Assert(t, visitLogString.String(), qt.CmpEquals(), fixtureExpectNormBuf.String())
+		})
+	}
+
+}