Fix index and slice expressions for query (#405)

* Fix index and slice expressions for query Support negative step for slice expressions
2020-05-14 08:21:51 +02:00
parent 44aed552fd
commit a60e466129
8 changed files with 601 additions and 182 deletions
@@ -0,0 +1,201 @@
+# Query package
+
+## Overview
+
+Package query performs JSONPath-like queries on a TOML document.
+
+The query path implementation is based loosely on the JSONPath specification:
+http://goessner.net/articles/JsonPath/.
+
+The idea behind a query path is to allow quick access to any element, or set
+of elements within TOML document, with a single expression.
+
+```go
+result, err := query.CompileAndExecute("$.foo.bar.baz", tree)
+```
+
+This is roughly equivalent to:
+
+```go
+next := tree.Get("foo")
+if next != nil {
+    next = next.Get("bar")
+    if next != nil {
+        next = next.Get("baz")
+    }
+}
+result := next
+```
+
+err is nil if any parsing exception occurs.
+
+If no node in the tree matches the query, result will simply contain an empty list of
+items.
+
+As illustrated above, the query path is much more efficient, especially since
+the structure of the TOML file can vary. Rather than making assumptions about
+a document's structure, a query allows the programmer to make structured
+requests into the document, and get zero or more values as a result.
+
+## Query syntax
+
+The syntax of a query begins with a root token, followed by any number
+sub-expressions:
+
+```
+$
+                    Root of the TOML tree. This must always come first.
+.name
+                    Selects child of this node, where 'name' is a TOML key
+                    name.
+['name']
+                    Selects child of this node, where 'name' is a string
+                    containing a TOML key name.
+[index]
+                    Selcts child array element at 'index'.
+..expr
+                    Recursively selects all children, filtered by an a union,
+                    index, or slice expression.
+..*
+                    Recursive selection of all nodes at this point in the
+                    tree.
+.*
+                    Selects all children of the current node.
+[expr,expr]
+                    Union operator - a logical 'or' grouping of two or more
+                    sub-expressions: index, key name, or filter.
+[start:end:step]
+                    Slice operator - selects array elements from start to
+                    end-1, at the given step. All three arguments are
+                    optional.
+[?(filter)]
+                    Named filter expression - the function 'filter' is
+                    used to filter children at this node.
+```
+
+## Query Indexes And Slices
+
+Index expressions perform no bounds checking, and will contribute no
+values to the result set if the provided index or index range is invalid.
+Negative indexes represent values from the end of the array, counting backwards.
+
+```go
+// select the last index of the array named 'foo'
+query.CompileAndExecute("$.foo[-1]", tree)
+```
+
+Slice expressions are supported, by using ':' to separate a start/end index pair.
+
+```go
+// select up to the first five elements in the array
+query.CompileAndExecute("$.foo[0:5]", tree)
+```
+
+Slice expressions also allow negative indexes for the start and stop
+arguments.
+
+```go
+// select all array elements except the last one.
+query.CompileAndExecute("$.foo[0:-1]", tree)
+```
+
+Slice expressions may have an optional stride/step parameter:
+
+```go
+// select every other element
+query.CompileAndExecute("$.foo[0::2]", tree)
+```
+
+Slice start and end parameters are also optional:
+
+```go
+// these are all equivalent and select all the values in the array
+query.CompileAndExecute("$.foo[:]", tree)
+query.CompileAndExecute("$.foo[::]", tree)
+query.CompileAndExecute("$.foo[::1]", tree)
+query.CompileAndExecute("$.foo[0:]", tree)
+query.CompileAndExecute("$.foo[0::]", tree)
+query.CompileAndExecute("$.foo[0::1]", tree)
+```
+
+## Query Filters
+
+Query filters are used within a Union [,] or single Filter [] expression.
+A filter only allows nodes that qualify through to the next expression,
+and/or into the result set.
+
+```go
+// returns children of foo that are permitted by the 'bar' filter.
+query.CompileAndExecute("$.foo[?(bar)]", tree)
+```
+
+There are several filters provided with the library:
+
+```
+tree
+        Allows nodes of type Tree.
+int
+        Allows nodes of type int64.
+float
+        Allows nodes of type float64.
+string
+        Allows nodes of type string.
+time
+        Allows nodes of type time.Time.
+bool
+        Allows nodes of type bool.
+```
+
+## Query Results
+
+An executed query returns a Result object. This contains the nodes
+in the TOML tree that qualify the query expression. Position information
+is also available for each value in the set.
+
+```go
+// display the results of a query
+results := query.CompileAndExecute("$.foo.bar.baz", tree)
+for idx, value := results.Values() {
+    fmt.Println("%v: %v", results.Positions()[idx], value)
+}
+```
+
+## Compiled Queries
+
+Queries may be executed directly on a Tree object, or compiled ahead
+of time and executed discretely. The former is more convenient, but has the
+penalty of having to recompile the query expression each time.
+
+```go
+// basic query
+results := query.CompileAndExecute("$.foo.bar.baz", tree)
+
+// compiled query
+query, err := toml.Compile("$.foo.bar.baz")
+results := query.Execute(tree)
+
+// run the compiled query again on a different tree
+moreResults := query.Execute(anotherTree)
+```
+
+## User Defined Query Filters
+
+Filter expressions may also be user defined by using the SetFilter()
+function on the Query object. The function must return true/false, which
+signifies if the passed node is kept or discarded, respectively.
+
+```go
+// create a query that references a user-defined filter
+query, _ := query.Compile("$[?(bazOnly)]")
+
+// define the filter, and assign it to the query
+query.SetFilter("bazOnly", func(node interface{}) bool{
+    if tree, ok := node.(*Tree); ok {
+        return tree.Has("baz")
+    }
+    return false // reject all other node types
+})
+
+// run the query
+query.Execute(tree)
+```
@@ -25,7 +25,7 @@
 // items.
 //
 // As illustrated above, the query path is much more efficient, especially since
-// the structure of the TOML file can vary.  Rather than making assumptions about
+// the structure of the TOML file can vary. Rather than making assumptions about
 // a document's structure, a query allows the programmer to make structured
 // requests into the document, and get zero or more values as a result.
 //
@@ -35,7 +35,7 @@
 // sub-expressions:
 //
 //   $
-//                    Root of the TOML tree.  This must always come first.
+//                    Root of the TOML tree. This must always come first.
 //   .name
 //                    Selects child of this node, where 'name' is a TOML key
 //                    name.
@@ -57,7 +57,7 @@
 //                    sub-expressions: index, key name, or filter.
 //   [start:end:step]
 //                    Slice operator - selects array elements from start to
-//                    end-1, at the given step.  All three arguments are
+//                    end-1, at the given step. All three arguments are
 //                    optional.
 //   [?(filter)]
 //                    Named filter expression - the function 'filter' is
@@ -80,25 +80,23 @@
 // Slice expressions also allow negative indexes for the start and stop
 // arguments.
 //
-//   // select all array elements.
+//   // select all array elements except the last one.
 //   query.CompileAndExecute("$.foo[0:-1]", tree)
 //
 // Slice expressions may have an optional stride/step parameter:
 //
 //   // select every other element
-//   query.CompileAndExecute("$.foo[0:-1:2]", tree)
+//   query.CompileAndExecute("$.foo[0::2]", tree)
 //
 // Slice start and end parameters are also optional:
 //
 //   // these are all equivalent and select all the values in the array
 //   query.CompileAndExecute("$.foo[:]", tree)
-//   query.CompileAndExecute("$.foo[0:]", tree)
-//   query.CompileAndExecute("$.foo[:-1]", tree)
-//   query.CompileAndExecute("$.foo[0:-1:]", tree)
+//   query.CompileAndExecute("$.foo[::]", tree)
 //   query.CompileAndExecute("$.foo[::1]", tree)
+//   query.CompileAndExecute("$.foo[0:]", tree)
+//   query.CompileAndExecute("$.foo[0::]", tree)
 //   query.CompileAndExecute("$.foo[0::1]", tree)
-//   query.CompileAndExecute("$.foo[:-1:1]", tree)
-//   query.CompileAndExecute("$.foo[0:-1:1]", tree)
 //
 // Query Filters
 //
@@ -126,8 +124,8 @@
 //
 // Query Results
 //
-// An executed query returns a Result object.  This contains the nodes
-// in the TOML tree that qualify the query expression.  Position information
+// An executed query returns a Result object. This contains the nodes
+// in the TOML tree that qualify the query expression. Position information
 // is also available for each value in the set.
 //
 //   // display the results of a query
@@ -139,7 +137,7 @@
 // Compiled Queries
 //
 // Queries may be executed directly on a Tree object, or compiled ahead
-// of time and executed discretely.  The former is more convenient, but has the
+// of time and executed discretely. The former is more convenient, but has the
 // penalty of having to recompile the query expression each time.
 //
 //   // basic query
@@ -155,7 +153,7 @@
 // User Defined Query Filters
 //
 // Filter expressions may also be user defined by using the SetFilter()
-// function on the Query object.  The function must return true/false, which
+// function on the Query object. The function must return true/false, which
 // signifies if the passed node is kept or discarded, respectively.
 //
 //   // create a query that references a user-defined filter
@@ -166,7 +164,7 @@
 //       if tree, ok := node.(*Tree); ok {
 //           return tree.Has("baz")
 //       }
-//       return false  // reject all other node types
+//       return false // reject all other node types
 //   })
 //
 //   // run the query
@@ -2,6 +2,7 @@ package query

 import (
 	"fmt"
+	"reflect"

 	"github.com/pelletier/go-toml"
 )
@@ -71,53 +72,130 @@ func newMatchIndexFn(idx int) *matchIndexFn {
 }

 func (f *matchIndexFn) call(node interface{}, ctx *queryContext) {
-	if arr, ok := node.([]interface{}); ok {
-		if f.Idx < len(arr) && f.Idx >= 0 {
-			if treesArray, ok := node.([]*toml.Tree); ok {
-				if len(treesArray) > 0 {
-					ctx.lastPosition = treesArray[0].Position()
-				}
-			}
-			f.next.call(arr[f.Idx], ctx)
+	v := reflect.ValueOf(node)
+	if v.Kind() == reflect.Slice {
+		if v.Len() == 0 {
+			return
+		}
+
+		// Manage negative values
+		idx := f.Idx
+		if idx < 0 {
+			idx += v.Len()
+		}
+		if 0 <= idx && idx < v.Len() {
+			callNextIndexSlice(f.next, node, ctx, v.Index(idx).Interface())
 		}
 	}
 }

+func callNextIndexSlice(next pathFn, node interface{}, ctx *queryContext, value interface{}) {
+	if treesArray, ok := node.([]*toml.Tree); ok {
+		ctx.lastPosition = treesArray[0].Position()
+	}
+	next.call(value, ctx)
+}
+
 // filter by slicing
 type matchSliceFn struct {
 	matchBase
-	Start, End, Step int
+	Start, End, Step *int
 }

-func newMatchSliceFn(start, end, step int) *matchSliceFn {
-	return &matchSliceFn{Start: start, End: end, Step: step}
+func newMatchSliceFn() *matchSliceFn {
+	return &matchSliceFn{}
+}
+
+func (f *matchSliceFn) setStart(start int) *matchSliceFn {
+	f.Start = &start
+	return f
+}
+
+func (f *matchSliceFn) setEnd(end int) *matchSliceFn {
+	f.End = &end
+	return f
+}
+
+func (f *matchSliceFn) setStep(step int) *matchSliceFn {
+	f.Step = &step
+	return f
 }

 func (f *matchSliceFn) call(node interface{}, ctx *queryContext) {
-	if arr, ok := node.([]interface{}); ok {
-		// adjust indexes for negative values, reverse ordering
-		realStart, realEnd := f.Start, f.End
-		if realStart < 0 {
-			realStart = len(arr) + realStart
+	v := reflect.ValueOf(node)
+	if v.Kind() == reflect.Slice {
+		if v.Len() == 0 {
+			return
 		}
-		if realEnd < 0 {
-			realEnd = len(arr) + realEnd
+
+		var start, end, step int
+
+		// Initialize step
+		if f.Step != nil {
+			step = *f.Step
+		} else {
+			step = 1
 		}
-		if realEnd < realStart {
-			realEnd, realStart = realStart, realEnd // swap
-		}
-		// loop and gather
-		for idx := realStart; idx < realEnd; idx += f.Step {
-			if treesArray, ok := node.([]*toml.Tree); ok {
-				if len(treesArray) > 0 {
-					ctx.lastPosition = treesArray[0].Position()
-				}
+
+		// Initialize start
+		if f.Start != nil {
+			start = *f.Start
+			// Manage negative values
+			if start < 0 {
+				start += v.Len()
+			}
+			// Manage out of range values
+			start = max(start, 0)
+			start = min(start, v.Len()-1)
+		} else if step > 0 {
+			start = 0
+		} else {
+			start = v.Len() - 1
+		}
+
+		// Initialize end
+		if f.End != nil {
+			end = *f.End
+			// Manage negative values
+			if end < 0 {
+				end += v.Len()
+			}
+			// Manage out of range values
+			end = max(end, -1)
+			end = min(end, v.Len())
+		} else if step > 0 {
+			end = v.Len()
+		} else {
+			end = -1
+		}
+
+		// Loop on values
+		if step > 0 {
+			for idx := start; idx < end; idx += step {
+				callNextIndexSlice(f.next, node, ctx, v.Index(idx).Interface())
+			}
+		} else {
+			for idx := start; idx > end; idx += step {
+				callNextIndexSlice(f.next, node, ctx, v.Index(idx).Interface())
 			}
-			f.next.call(arr[idx], ctx)
 		}
 	}
 }

+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+
 // match anything
 type matchAnyFn struct {
 	matchBase
@@ -2,8 +2,10 @@ package query

 import (
 	"fmt"
-	"github.com/pelletier/go-toml"
+	"strconv"
 	"testing"
+
+	"github.com/pelletier/go-toml"
 )

 // dump path tree to a string
@@ -19,8 +21,17 @@ func pathString(root pathFn) string {
 		result += fmt.Sprintf("{%d}", fn.Idx)
 		result += pathString(fn.next)
 	case *matchSliceFn:
-		result += fmt.Sprintf("{%d:%d:%d}",
-			fn.Start, fn.End, fn.Step)
+		startString, endString, stepString := "nil", "nil", "nil"
+		if fn.Start != nil {
+			startString = strconv.Itoa(*fn.Start)
+		}
+		if fn.End != nil {
+			endString = strconv.Itoa(*fn.End)
+		}
+		if fn.Step != nil {
+			stepString = strconv.Itoa(*fn.Step)
+		}
+		result += fmt.Sprintf("{%s:%s:%s}", startString, endString, stepString)
 		result += pathString(fn.next)
 	case *matchAnyFn:
 		result += "{}"
@@ -110,7 +121,7 @@ func TestPathSliceStart(t *testing.T) {
 	assertPath(t,
 		"$[123:]",
 		buildPath(
-			newMatchSliceFn(123, maxInt, 1),
+			newMatchSliceFn().setStart(123),
 		))
 }

@@ -118,7 +129,7 @@ func TestPathSliceStartEnd(t *testing.T) {
 	assertPath(t,
 		"$[123:456]",
 		buildPath(
-			newMatchSliceFn(123, 456, 1),
+			newMatchSliceFn().setStart(123).setEnd(456),
 		))
 }

@@ -126,7 +137,7 @@ func TestPathSliceStartEndColon(t *testing.T) {
 	assertPath(t,
 		"$[123:456:]",
 		buildPath(
-			newMatchSliceFn(123, 456, 1),
+			newMatchSliceFn().setStart(123).setEnd(456),
 		))
 }

@@ -134,7 +145,7 @@ func TestPathSliceStartStep(t *testing.T) {
 	assertPath(t,
 		"$[123::7]",
 		buildPath(
-			newMatchSliceFn(123, maxInt, 7),
+			newMatchSliceFn().setStart(123).setStep(7),
 		))
 }

@@ -142,7 +153,7 @@ func TestPathSliceEndStep(t *testing.T) {
 	assertPath(t,
 		"$[:456:7]",
 		buildPath(
-			newMatchSliceFn(0, 456, 7),
+			newMatchSliceFn().setEnd(456).setStep(7),
 		))
 }

@@ -150,7 +161,7 @@ func TestPathSliceStep(t *testing.T) {
 	assertPath(t,
 		"$[::7]",
 		buildPath(
-			newMatchSliceFn(0, maxInt, 7),
+			newMatchSliceFn().setStep(7),
 		))
 }

@@ -158,7 +169,7 @@ func TestPathSliceAll(t *testing.T) {
 	assertPath(t,
 		"$[123:456:7]",
 		buildPath(
-			newMatchSliceFn(123, 456, 7),
+			newMatchSliceFn().setStart(123).setEnd(456).setStep(7),
 		))
 }

@@ -203,12 +203,13 @@ loop: // labeled loop for easy breaking

 func (p *queryParser) parseSliceExpr() queryParserStateFn {
 	// init slice to grab all elements
-	start, end, step := 0, maxInt, 1
+	var start, end, step *int = nil, nil, nil

 	// parse optional start
 	tok := p.getToken()
 	if tok.typ == tokenInteger {
-		start = tok.Int()
+		v := tok.Int()
+		start = &v
 		tok = p.getToken()
 	}
 	if tok.typ != tokenColon {
@@ -218,11 +219,12 @@ func (p *queryParser) parseSliceExpr() queryParserStateFn {
 	// parse optional end
 	tok = p.getToken()
 	if tok.typ == tokenInteger {
-		end = tok.Int()
+		v := tok.Int()
+		end = &v
 		tok = p.getToken()
 	}
 	if tok.typ == tokenRightBracket {
-		p.query.appendPath(newMatchSliceFn(start, end, step))
+		p.query.appendPath(&matchSliceFn{Start: start, End: end, Step: step})
 		return p.parseMatchExpr
 	}
 	if tok.typ != tokenColon {
@@ -232,17 +234,18 @@ func (p *queryParser) parseSliceExpr() queryParserStateFn {
 	// parse optional step
 	tok = p.getToken()
 	if tok.typ == tokenInteger {
-		step = tok.Int()
-		if step < 0 {
-			return p.parseError(tok, "step must be a positive value")
+		v := tok.Int()
+		if v == 0 {
+			return p.parseError(tok, "step cannot be zero")
 		}
+		step = &v
 		tok = p.getToken()
 	}
 	if tok.typ != tokenRightBracket {
 		return p.parseError(tok, "expected ']'")
 	}

-	p.query.appendPath(newMatchSliceFn(start, end, step))
+	p.query.appendPath(&matchSliceFn{Start: start, End: end, Step: step})
 	return p.parseMatchExpr
 }

@@ -78,6 +78,19 @@ func assertValue(t *testing.T, result, ref interface{}) {
 	}
 }

+func assertParseError(t *testing.T, query string, errString string) {
+	_, err := Compile(query)
+	if err == nil {
+		t.Error("error should be non-nil")
+		return
+	}
+	if err.Error() != errString {
+		t.Errorf("error does not match")
+		t.Log("test:", err.Error())
+		t.Log("ref: ", errString)
+	}
+}
+
 func assertQueryPositions(t *testing.T, tomlDoc string, query string, ref []interface{}) {
 	tree, err := toml.Load(tomlDoc)
 	if err != nil {
@@ -128,54 +141,213 @@ func TestQueryKeyString(t *testing.T) {
 		})
 }

-func TestQueryIndex(t *testing.T) {
+func TestQueryKeyUnicodeString(t *testing.T) {
 	assertQueryPositions(t,
-		"[foo]\na = [1,2,3,4,5,6,7,8,9,0]",
-		"$.foo.a[5]",
+		"['f𝟘.o']\na = 42",
+		"$['f𝟘.o']['a']",
 		[]interface{}{
 			queryTestNode{
-				int64(6), toml.Position{2, 1},
+				int64(42), toml.Position{2, 1},
 			},
 		})
 }

+func TestQueryIndexError1(t *testing.T) {
+	assertParseError(t, "$.foo.a[5", "(1, 10): expected ',' or ']', not ''")
+}
+
+func TestQueryIndexError2(t *testing.T) {
+	assertParseError(t, "$.foo.a[]", "(1, 9): expected union sub expression, not ']', 0")
+}
+
+func TestQueryIndex(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[5]",
+		[]interface{}{
+			queryTestNode{int64(5), toml.Position{2, 1}},
+		})
+}
+
+func TestQueryIndexNegative(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[-2]",
+		[]interface{}{
+			queryTestNode{int64(8), toml.Position{2, 1}},
+		})
+}
+
+func TestQueryIndexWrong(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[99]",
+		[]interface{}{})
+}
+
+func TestQueryIndexEmpty(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = []",
+		"$.foo.a[5]",
+		[]interface{}{})
+}
+
+func TestQueryIndexTree(t *testing.T) {
+	assertQueryPositions(t,
+		"[[foo]]\na = [0,1,2,3,4,5,6,7,8,9]\n[[foo]]\nb = 3",
+		"$.foo[1].b",
+		[]interface{}{
+			queryTestNode{int64(3), toml.Position{4, 1}},
+		})
+}
+
+func TestQuerySliceError1(t *testing.T) {
+	assertParseError(t, "$.foo.a[3:?]", "(1, 11): expected ']' or ':'")
+}
+
+func TestQuerySliceError2(t *testing.T) {
+	assertParseError(t, "$.foo.a[:::]", "(1, 11): expected ']'")
+}
+
+func TestQuerySliceError3(t *testing.T) {
+	assertParseError(t, "$.foo.a[::0]", "(1, 11): step cannot be zero")
+}
+
 func TestQuerySliceRange(t *testing.T) {
 	assertQueryPositions(t,
-		"[foo]\na = [1,2,3,4,5,6,7,8,9,0]",
-		"$.foo.a[0:5]",
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[:5]",
 		[]interface{}{
-			queryTestNode{
-				int64(1), toml.Position{2, 1},
-			},
-			queryTestNode{
-				int64(2), toml.Position{2, 1},
-			},
-			queryTestNode{
-				int64(3), toml.Position{2, 1},
-			},
-			queryTestNode{
-				int64(4), toml.Position{2, 1},
-			},
-			queryTestNode{
-				int64(5), toml.Position{2, 1},
-			},
+			queryTestNode{int64(0), toml.Position{2, 1}},
+			queryTestNode{int64(1), toml.Position{2, 1}},
+			queryTestNode{int64(2), toml.Position{2, 1}},
+			queryTestNode{int64(3), toml.Position{2, 1}},
+			queryTestNode{int64(4), toml.Position{2, 1}},
 		})
 }

 func TestQuerySliceStep(t *testing.T) {
 	assertQueryPositions(t,
-		"[foo]\na = [1,2,3,4,5,6,7,8,9,0]",
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
 		"$.foo.a[0:5:2]",
+		[]interface{}{
+			queryTestNode{int64(0), toml.Position{2, 1}},
+			queryTestNode{int64(2), toml.Position{2, 1}},
+			queryTestNode{int64(4), toml.Position{2, 1}},
+		})
+}
+
+func TestQuerySliceStartNegative(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[-3:]",
+		[]interface{}{
+			queryTestNode{int64(7), toml.Position{2, 1}},
+			queryTestNode{int64(8), toml.Position{2, 1}},
+			queryTestNode{int64(9), toml.Position{2, 1}},
+		})
+}
+
+func TestQuerySliceEndNegative(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[:-6]",
+		[]interface{}{
+			queryTestNode{int64(0), toml.Position{2, 1}},
+			queryTestNode{int64(1), toml.Position{2, 1}},
+			queryTestNode{int64(2), toml.Position{2, 1}},
+			queryTestNode{int64(3), toml.Position{2, 1}},
+		})
+}
+
+func TestQuerySliceStepNegative(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[::-2]",
+		[]interface{}{
+			queryTestNode{int64(9), toml.Position{2, 1}},
+			queryTestNode{int64(7), toml.Position{2, 1}},
+			queryTestNode{int64(5), toml.Position{2, 1}},
+			queryTestNode{int64(3), toml.Position{2, 1}},
+			queryTestNode{int64(1), toml.Position{2, 1}},
+		})
+}
+
+func TestQuerySliceStartOverRange(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[-99:3]",
+		[]interface{}{
+			queryTestNode{int64(0), toml.Position{2, 1}},
+			queryTestNode{int64(1), toml.Position{2, 1}},
+			queryTestNode{int64(2), toml.Position{2, 1}},
+		})
+}
+
+func TestQuerySliceStartOverRangeNegative(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[99:7:-1]",
+		[]interface{}{
+			queryTestNode{int64(9), toml.Position{2, 1}},
+			queryTestNode{int64(8), toml.Position{2, 1}},
+		})
+}
+
+func TestQuerySliceEndOverRange(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[7:99]",
+		[]interface{}{
+			queryTestNode{int64(7), toml.Position{2, 1}},
+			queryTestNode{int64(8), toml.Position{2, 1}},
+			queryTestNode{int64(9), toml.Position{2, 1}},
+		})
+}
+
+func TestQuerySliceEndOverRangeNegative(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[2:-99:-1]",
+		[]interface{}{
+			queryTestNode{int64(2), toml.Position{2, 1}},
+			queryTestNode{int64(1), toml.Position{2, 1}},
+			queryTestNode{int64(0), toml.Position{2, 1}},
+		})
+}
+
+func TestQuerySliceWrongRange(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[5:3]",
+		[]interface{}{})
+}
+
+func TestQuerySliceWrongRangeNegative(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = [0,1,2,3,4,5,6,7,8,9]",
+		"$.foo.a[3:5:-1]",
+		[]interface{}{})
+}
+
+func TestQuerySliceEmpty(t *testing.T) {
+	assertQueryPositions(t,
+		"[foo]\na = []",
+		"$.foo.a[5:]",
+		[]interface{}{})
+}
+
+func TestQuerySliceTree(t *testing.T) {
+	assertQueryPositions(t,
+		"[[foo]]\na='nok'\n[[foo]]\na = [0,1,2,3,4,5,6,7,8,9]\n[[foo]]\na='ok'\nb = 3",
+		"$.foo[1:].a",
 		[]interface{}{
 			queryTestNode{
-				int64(1), toml.Position{2, 1},
-			},
-			queryTestNode{
-				int64(3), toml.Position{2, 1},
-			},
-			queryTestNode{
-				int64(5), toml.Position{2, 1},
-			},
+				[]interface{}{
+					int64(0), int64(1), int64(2), int64(3), int64(4),
+					int64(5), int64(6), int64(7), int64(8), int64(9)},
+				toml.Position{4, 1}},
+			queryTestNode{"ok", toml.Position{6, 1}},
 		})
 }

@@ -265,12 +437,8 @@ func TestQueryRecursionAll(t *testing.T) {
 					"b": int64(2),
 				}, toml.Position{1, 1},
 			},
-			queryTestNode{
-				int64(1), toml.Position{2, 1},
-			},
-			queryTestNode{
-				int64(2), toml.Position{3, 1},
-			},
+			queryTestNode{int64(1), toml.Position{2, 1}},
+			queryTestNode{int64(2), toml.Position{3, 1}},
 			queryTestNode{
 				map[string]interface{}{
 					"foo": map[string]interface{}{
@@ -285,12 +453,8 @@ func TestQueryRecursionAll(t *testing.T) {
 					"b": int64(4),
 				}, toml.Position{4, 1},
 			},
-			queryTestNode{
-				int64(3), toml.Position{5, 1},
-			},
-			queryTestNode{
-				int64(4), toml.Position{6, 1},
-			},
+			queryTestNode{int64(3), toml.Position{5, 1}},
+			queryTestNode{int64(4), toml.Position{6, 1}},
 			queryTestNode{
 				map[string]interface{}{
 					"foo": map[string]interface{}{
@@ -305,12 +469,8 @@ func TestQueryRecursionAll(t *testing.T) {
 					"b": int64(6),
 				}, toml.Position{7, 1},
 			},
-			queryTestNode{
-				int64(5), toml.Position{8, 1},
-			},
-			queryTestNode{
-				int64(6), toml.Position{9, 1},
-			},
+			queryTestNode{int64(5), toml.Position{8, 1}},
+			queryTestNode{int64(6), toml.Position{9, 1}},
 		})
 }

@@ -358,59 +518,30 @@ func TestQueryFilterFn(t *testing.T) {
 	assertQueryPositions(t, string(buff),
 		"$..[?(int)]",
 		[]interface{}{
-			queryTestNode{
-				int64(8001), toml.Position{13, 1},
-			},
-			queryTestNode{
-				int64(8001), toml.Position{13, 1},
-			},
-			queryTestNode{
-				int64(8002), toml.Position{13, 1},
-			},
-			queryTestNode{
-				int64(5000), toml.Position{14, 1},
-			},
+			queryTestNode{int64(8001), toml.Position{13, 1}},
+			queryTestNode{int64(8001), toml.Position{13, 1}},
+			queryTestNode{int64(8002), toml.Position{13, 1}},
+			queryTestNode{int64(5000), toml.Position{14, 1}},
 		})

 	assertQueryPositions(t, string(buff),
 		"$..[?(string)]",
 		[]interface{}{
-			queryTestNode{
-				"TOML Example", toml.Position{3, 1},
-			},
-			queryTestNode{
-				"Tom Preston-Werner", toml.Position{6, 1},
-			},
-			queryTestNode{
-				"GitHub", toml.Position{7, 1},
-			},
-			queryTestNode{
-				"GitHub Cofounder & CEO\nLikes tater tots and beer.",
-				toml.Position{8, 1},
-			},
-			queryTestNode{
-				"192.168.1.1", toml.Position{12, 1},
-			},
-			queryTestNode{
-				"10.0.0.1", toml.Position{21, 3},
-			},
-			queryTestNode{
-				"eqdc10", toml.Position{22, 3},
-			},
-			queryTestNode{
-				"10.0.0.2", toml.Position{25, 3},
-			},
-			queryTestNode{
-				"eqdc10", toml.Position{26, 3},
-			},
+			queryTestNode{"TOML Example", toml.Position{3, 1}},
+			queryTestNode{"Tom Preston-Werner", toml.Position{6, 1}},
+			queryTestNode{"GitHub", toml.Position{7, 1}},
+			queryTestNode{"GitHub Cofounder & CEO\nLikes tater tots and beer.", toml.Position{8, 1}},
+			queryTestNode{"192.168.1.1", toml.Position{12, 1}},
+			queryTestNode{"10.0.0.1", toml.Position{21, 3}},
+			queryTestNode{"eqdc10", toml.Position{22, 3}},
+			queryTestNode{"10.0.0.2", toml.Position{25, 3}},
+			queryTestNode{"eqdc10", toml.Position{26, 3}},
 		})

 	assertQueryPositions(t, string(buff),
 		"$..[?(float)]",
-		[]interface{}{ 
-			queryTestNode{
-				4e-08, toml.Position{30, 1},
-			},
+		[]interface{}{
+			queryTestNode{4e-08, toml.Position{30, 1}},
 		})

 	tv, _ := time.Parse(time.RFC3339, "1979-05-27T07:32:00Z")
@@ -471,16 +602,12 @@ func TestQueryFilterFn(t *testing.T) {
 	assertQueryPositions(t, string(buff),
 		"$..[?(time)]",
 		[]interface{}{
-			queryTestNode{
-				tv, toml.Position{9, 1},
-			},
+			queryTestNode{tv, toml.Position{9, 1}},
 		})

 	assertQueryPositions(t, string(buff),
 		"$..[?(bool)]",
 		[]interface{}{
-			queryTestNode{
-				true, toml.Position{15, 1},
-			},
+			queryTestNode{true, toml.Position{15, 1}},
 		})
 }
@@ -26,6 +26,14 @@ func assertArrayContainsInAnyOrder(t *testing.T, array []interface{}, objects ..
 	}
 }

+func checkQuery(t *testing.T, tree *toml.Tree, query string, objects ...interface{}) {
+	results, err := CompileAndExecute(query, tree)
+	if err != nil {
+		t.Fatal("unexpected error:", err)
+	}
+	assertArrayContainsInAnyOrder(t, results.Values(), objects...)
+}
+
 func TestQueryExample(t *testing.T) {
 	config, _ := toml.Load(`
      [[book]]
@@ -37,16 +45,18 @@ func TestQueryExample(t *testing.T) {
      [[book]]
      title = "Neuromancer"
      author = "William Gibson"
-    `)
-	authors, err := CompileAndExecute("$.book.author", config)
-	if err != nil {
-		t.Fatal("unexpected error:", err)
-	}
-	names := authors.Values()
-	if len(names) != 3 {
-		t.Fatalf("query should return 3 names but returned %d", len(names))
-	}
-	assertArrayContainsInAnyOrder(t, names, "Stephen King", "Ernest Hemmingway", "William Gibson")
+	`)
+
+	checkQuery(t, config, "$.book.author", "Stephen King", "Ernest Hemmingway", "William Gibson")
+
+	checkQuery(t, config, "$.book[0].author", "Stephen King")
+	checkQuery(t, config, "$.book[-1].author", "William Gibson")
+	checkQuery(t, config, "$.book[1:].author", "Ernest Hemmingway", "William Gibson")
+	checkQuery(t, config, "$.book[-1:].author", "William Gibson")
+	checkQuery(t, config, "$.book[::2].author", "William Gibson", "Stephen King")
+	checkQuery(t, config, "$.book[::-1].author", "William Gibson", "Ernest Hemmingway", "Stephen King")
+	checkQuery(t, config, "$.book[:].author", "Stephen King", "Ernest Hemmingway", "William Gibson")
+	checkQuery(t, config, "$.book[::].author", "Stephen King", "Ernest Hemmingway", "William Gibson")
 }

 func TestQueryReadmeExample(t *testing.T) {
@@ -56,16 +66,7 @@ user = "pelletier"
 password = "mypassword"
 `)

-	query, err := Compile("$..[user,password]")
-	if err != nil {
-		t.Fatal("unexpected error:", err)
-	}
-	results := query.Execute(config)
-	values := results.Values()
-	if len(values) != 2 {
-		t.Fatalf("query should return 2 values but returned %d", len(values))
-	}
-	assertArrayContainsInAnyOrder(t, values, "pelletier", "mypassword")
+	checkQuery(t, config, "$..[user,password]", "pelletier", "mypassword")
 }

 func TestQueryPathNotPresent(t *testing.T) {