Move query to its own subpackage (#152)

Move all the query system to its own package. The reason is to
avoid it to rely on unexported methods and structures, and move
it out of the main package since this is really not a core
feature. It is still tied to the toml.TomlTree and toml.Position
structures for now.

* Move query mechanism to its own subpackage
* Rename QueryResult to Result to avoid stutter
* Add query.CompileAndExecute

Fixes #116

query/match_test.go

@@ -0,0 +1,202 @@
+package query
+
+import (
+	"fmt"
+	"testing"
+	"github.com/pelletier/go-toml"
+)
+
+// dump path tree to a string
+func pathString(root pathFn) string {
+	result := fmt.Sprintf("%T:", root)
+	switch fn := root.(type) {
+	case *terminatingFn:
+		result += "{}"
+	case *matchKeyFn:
+		result += fmt.Sprintf("{%s}", fn.Name)
+		result += pathString(fn.next)
+	case *matchIndexFn:
+		result += fmt.Sprintf("{%d}", fn.Idx)
+		result += pathString(fn.next)
+	case *matchSliceFn:
+		result += fmt.Sprintf("{%d:%d:%d}",
+			fn.Start, fn.End, fn.Step)
+		result += pathString(fn.next)
+	case *matchAnyFn:
+		result += "{}"
+		result += pathString(fn.next)
+	case *matchUnionFn:
+		result += "{["
+		for _, v := range fn.Union {
+			result += pathString(v) + ", "
+		}
+		result += "]}"
+	case *matchRecursiveFn:
+		result += "{}"
+		result += pathString(fn.next)
+	case *matchFilterFn:
+		result += fmt.Sprintf("{%s}", fn.Name)
+		result += pathString(fn.next)
+	}
+	return result
+}
+
+func assertPathMatch(t *testing.T, path, ref *Query) bool {
+	pathStr := pathString(path.root)
+	refStr := pathString(ref.root)
+	if pathStr != refStr {
+		t.Errorf("paths do not match")
+		t.Log("test:", pathStr)
+		t.Log("ref: ", refStr)
+		return false
+	}
+	return true
+}
+
+func assertPath(t *testing.T, query string, ref *Query) {
+	path, _ := parseQuery(lexQuery(query))
+	assertPathMatch(t, path, ref)
+}
+
+func buildPath(parts ...pathFn) *Query {
+	query := newQuery()
+	for _, v := range parts {
+		query.appendPath(v)
+	}
+	return query
+}
+
+func TestPathRoot(t *testing.T) {
+	assertPath(t,
+		"$",
+		buildPath(
+		// empty
+		))
+}
+
+func TestPathKey(t *testing.T) {
+	assertPath(t,
+		"$.foo",
+		buildPath(
+			newMatchKeyFn("foo"),
+		))
+}
+
+func TestPathBracketKey(t *testing.T) {
+	assertPath(t,
+		"$[foo]",
+		buildPath(
+			newMatchKeyFn("foo"),
+		))
+}
+
+func TestPathBracketStringKey(t *testing.T) {
+	assertPath(t,
+		"$['foo']",
+		buildPath(
+			newMatchKeyFn("foo"),
+		))
+}
+
+func TestPathIndex(t *testing.T) {
+	assertPath(t,
+		"$[123]",
+		buildPath(
+			newMatchIndexFn(123),
+		))
+}
+
+func TestPathSliceStart(t *testing.T) {
+	assertPath(t,
+		"$[123:]",
+		buildPath(
+			newMatchSliceFn(123, maxInt, 1),
+		))
+}
+
+func TestPathSliceStartEnd(t *testing.T) {
+	assertPath(t,
+		"$[123:456]",
+		buildPath(
+			newMatchSliceFn(123, 456, 1),
+		))
+}
+
+func TestPathSliceStartEndColon(t *testing.T) {
+	assertPath(t,
+		"$[123:456:]",
+		buildPath(
+			newMatchSliceFn(123, 456, 1),
+		))
+}
+
+func TestPathSliceStartStep(t *testing.T) {
+	assertPath(t,
+		"$[123::7]",
+		buildPath(
+			newMatchSliceFn(123, maxInt, 7),
+		))
+}
+
+func TestPathSliceEndStep(t *testing.T) {
+	assertPath(t,
+		"$[:456:7]",
+		buildPath(
+			newMatchSliceFn(0, 456, 7),
+		))
+}
+
+func TestPathSliceStep(t *testing.T) {
+	assertPath(t,
+		"$[::7]",
+		buildPath(
+			newMatchSliceFn(0, maxInt, 7),
+		))
+}
+
+func TestPathSliceAll(t *testing.T) {
+	assertPath(t,
+		"$[123:456:7]",
+		buildPath(
+			newMatchSliceFn(123, 456, 7),
+		))
+}
+
+func TestPathAny(t *testing.T) {
+	assertPath(t,
+		"$.*",
+		buildPath(
+			newMatchAnyFn(),
+		))
+}
+
+func TestPathUnion(t *testing.T) {
+	assertPath(t,
+		"$[foo, bar, baz]",
+		buildPath(
+			&matchUnionFn{[]pathFn{
+				newMatchKeyFn("foo"),
+				newMatchKeyFn("bar"),
+				newMatchKeyFn("baz"),
+			}},
+		))
+}
+
+func TestPathRecurse(t *testing.T) {
+	assertPath(t,
+		"$..*",
+		buildPath(
+			newMatchRecursiveFn(),
+		))
+}
+
+func TestPathFilterExpr(t *testing.T) {
+	assertPath(t,
+		"$[?('foo'),?(bar)]",
+		buildPath(
+			&matchUnionFn{[]pathFn{
+				newMatchFilterFn("foo", toml.Position{}),
+				newMatchFilterFn("bar", toml.Position{}),
+			}},
+		))
+}