Expressions (#21)

CHANGELOG.md

@@ -1,16 +1,25 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
 ## [Unreleased]
+
+## [0.3.0] - 2021-02-18
 ### Added
 - `JsonPathMatch.context` contains the matching context. It is intended to be used in named filters.
 - `JsonPathMatch.parent` contains the parent match.
 - `JsonPathMatch.pointer` contains the RFC 6901 JSON Pointer to the match.
+- Very basic support for evaluated expressions
 
 ### Changed
 - Named filters argument renamed from `filter` to `filters`
 - Named filters can now be passed to the `read()` method.
 - Named filters callback now accepts the entire `JsonPathMatch` object, not just the value.
 
 ### Removed
-- The `set()` method. The intention is to allow modifications via JSON Pointer in the future.
+- The `set()` method. Use the `pointer` property instead.
 
 ## [0.2.0] - 2020-09-07
 ### Added
@@ -83,7 +92,8 @@ Previously, no modification would be made and no errors/exceptions thrown.
 ### Added
 - Basic design draft
 
-[Unreleased]: https://github.com/f3ath/jessie/compare/0.2.0...HEAD
+[Unreleased]: https://github.com/f3ath/jessie/compare/0.3.0...HEAD
+[0.3.0]: https://github.com/f3ath/jessie/compare/0.2.0...0.3.0
 [0.2.0]: https://github.com/f3ath/jessie/compare/0.1.2...0.2.0
 [0.1.2]: https://github.com/f3ath/jessie/compare/0.1.1...0.1.2
 [0.1.1]: https://github.com/f3ath/jessie/compare/0.1.0...0.1.1

README.md

@@ -65,7 +65,7 @@ void main() {
 
 ## Features and limitations
 Generally, this library tries to mimic the [reference implementations], except for the filtering.
-Evaluated filtering expressions like `$..book[?(@.price<10)]` are NOT yet supported. 
+Evaluated filtering expressions (e.g. `$..book[?(@.price<10)]`) support is limited. 
 Instead, use the callback-kind of filters.
 ```dart
 /// Select all elements with price under 20

lib/src/grammar/expression.dart

@@ -4,50 +4,56 @@ import 'package:json_path/src/selector/expression_filter.dart';
 import 'package:petitparser/petitparser.dart';
 
 Parser<Eval> _build() {
-  final _true = string('true').trim().map<bool>((value) => true);
-  final _false = string('false').trim().map<bool>((value) => false);
-
-  final _literal =
-      (_false | _true | integer | doubleQuotedString | singleQuotedString)
-          .map<Eval>((value) => (match) => value);
-
-  final _term = undefined();
-
-  final _parens = (char('(').trim() & _term & char(')').trim())
-      .map((value) => (match) => value[1](match));
+  final _true = string('true').map((_) => true);
+  final _false = string('false').map((_) => false);
+  final _null = string('null').map((_) => null);
+
+  final _literal = (_false |
+          _true |
+          _null |
+          integer |
+          doubleQuotedString |
+          singleQuotedString)
+      .map<Eval>((value) => (match) => value);
 
   final _index = (char('[') &
           (integer | doubleQuotedString | singleQuotedString) &
           char(']'))
       .map((value) => value[1])
-      .map<Eval>((value) => (match) {
-            final key = value;
-            final v = match.value;
+      .map((key) => (v) {
             if (key is int && v is List && key < v.length && key >= 0) {
               return v[key];
             } else if (key is String && v is Map && v.containsKey(key)) {
               return v[key];
             }
           });
 
-  final _dotName = (char('.') & dotString).map((value) => (match) {
+  final _dotName = (char('.') & dotString).map((value) => (v) {
         final key = value.last;
-        final v = match.value;
         if (v is Map && v.containsKey(key)) {
           return v[key];
         }
       });
 
-  final _nodeMapper = _index | _dotName;
+  final _nodeFilter = (_index | _dotName)
+      .plus()
+      .map(
+          (value) => value.reduce((value, element) => (v) => element(value(v))))
+      .map<Eval>((value) => (match) => value(match.value));
+
+  final _node = (char('@') & _nodeFilter).map((value) => value.last);
+
+  final _term = undefined();
 
-  final _node = (char('@') & _nodeMapper).map<Eval>((value) => value.last);
+  final _parens =
+      (char('(').trim() & _term & char(')').trim()).map((value) => value[1]);
 
   final _comparable = _parens | _literal | _node;
 
   final _comparison = (_comparable & string('==').trim() & _comparable)
       .map((value) => (match) => value.first(match) == value.last(match));
 
-  _term.set(_comparison | _parens | _literal | _node);
+  _term.set(_comparison | _comparable);
 
   return (string('?(') & _term & char(')')).map((value) => value[1]);
 }

lib/src/matching_context.dart

@@ -1,8 +1,17 @@
+import 'package:json_path/src/filter_not_found.dart';
 import 'package:json_path/src/json_path_match.dart';
 
 class MatchingContext {
-  const MatchingContext(this.filters);
+  const MatchingContext(this._filters);
 
   /// Named callback filters
-  final Map<String, CallbackFilter> filters;
+  final Map<String, CallbackFilter> _filters;
+
+  CallbackFilter getFilter(String name) {
+    final filter = _filters[name];
+    if (filter == null) {
+      throw FilterNotFound('Callback filter "$name" not found');
+    }
+    return filter;
+  }
 }

lib/src/selector/callback_filter.dart

@@ -1,19 +1,12 @@
-import 'package:json_path/src/filter_not_found.dart';
 import 'package:json_path/src/json_path_match.dart';
-import 'package:json_path/src/selector.dart';
 import 'package:json_path/src/selector/wildcard.dart';
 
-class CallbackFilter implements Selector {
-  CallbackFilter(this.name);
+class CallbackFilter extends Wildcard {
+  const CallbackFilter(this.name);
 
   final String name;
 
   @override
-  Iterable<JsonPathMatch> apply(JsonPathMatch match) sync* {
-    final filter = match.context.filters[name];
-    if (filter == null) {
-      throw FilterNotFound('Callback filter "$name" not found');
-    }
-    yield* const Wildcard().apply(match).where(filter);
-  }
+  Iterable<JsonPathMatch> apply(JsonPathMatch match) =>
+      super.apply(match).where(match.context.getFilter(name));
 }

lib/src/selector/expression_filter.dart

@@ -1,21 +1,19 @@
 import 'package:json_path/src/json_path_match.dart';
-import 'package:json_path/src/selector.dart';
 import 'package:json_path/src/selector/wildcard.dart';
 
-class ExpressionFilter implements Selector {
+class ExpressionFilter extends Wildcard {
   ExpressionFilter(this.eval);
 
   final Eval eval;
 
   @override
-  Iterable<JsonPathMatch> apply(JsonPathMatch match) sync* {
-    yield* const Wildcard().apply(match).where((match) {
-      final val = eval(match);
-      return (val == true ||
-          (val is num && val != 0) ||
-          (val is String && val.isNotEmpty));
-    });
-  }
+  Iterable<JsonPathMatch> apply(JsonPathMatch match) =>
+      super.apply(match).where((match) {
+        final val = eval(match);
+        return (val == true ||
+            (val is num && val != 0) ||
+            (val is String && val.isNotEmpty));
+      });
 }
 
 typedef Eval<T> = T Function(JsonPathMatch match);

lib/src/selector/sequence.dart

@@ -1,18 +1,18 @@
 import 'package:json_path/src/json_path_match.dart';
 import 'package:json_path/src/selector.dart';
 
-typedef Filter = Iterable<JsonPathMatch> Function(
-    Iterable<JsonPathMatch> matches);
-
 class Sequence implements Selector {
   Sequence(Iterable<Selector> selectors)
-      : _filter = selectors.fold<Filter>(
+      : _filter = selectors.fold<_Filter>(
             (_) => _,
             (filter, selector) => (matches) =>
                 filter(matches).map(selector.apply).expand((_) => _));
 
-  final Filter _filter;
+  final _Filter _filter;
 
   @override
   Iterable<JsonPathMatch> apply(JsonPathMatch match) => _filter([match]);
 }
+
+typedef _Filter = Iterable<JsonPathMatch> Function(
+    Iterable<JsonPathMatch> matches);

pubspec.yaml

@@ -1,19 +1,18 @@
 name: json_path
-version: 0.3.0-nullsafety.3
-description: Implementation of JSONPath expressions like "$.store.book[2].price". Can read and set values in parsed JSON objects.
+version: 0.3.0
+description: Implementation of JSONPath expressions like "$.store.book[2].price". Reads and writes values in parsed JSON objects.
 homepage: "https://github.com/f3ath/jessie"
 
 environment:
   sdk: '>=2.12.0-29 <3.0.0'
 
 dependencies:
-  rfc_6901: ^0.0.0-nullsafety.7
-  petitparser: ^4.0.0-nullsafety
+  rfc_6901: ^0.1.0
+  petitparser: ^4.0.0
 
 dev_dependencies:
-  pedantic: ^1.10.0-nullsafety
-  test: ^1.16.0-nullsafety
+  pedantic: ^1.10.0
+  test: ^1.16.2
   test_coverage: ^0.5.0
-  path: ^1.8.0-nullsafety
-  yaml: ^3.0.0-nullsafety
+  path: ^1.8.0
 

test/cases/expressions.json

@@ -93,11 +93,25 @@
       "pointers": ["/1"]
     }, {
       "name": "object child, dot-notation",
-      "selector": "$[?(@.key == 'b')]",
+      "selector": "$[?(@.key=='b')]",
       "document": [{"key": "a"}, {"key": "b"}, {}],
       "values": [{"key": "b"}],
       "paths": ["$[1]"],
       "pointers": ["/1"]
+    }, {
+      "name": "object child, combined",
+      "selector": "$[?(@.foo['bar'] == 'b')]",
+      "document": [{"foo": {"bar": "a"}}, {"foo": {"bar": "b"}}, {"foo": {"moo": 42}}, {}],
+      "values": [{"foo": {"bar": "b"}}],
+      "paths": ["$[1]"],
+      "pointers": ["/1"]
+    }, {
+      "name": "equal props",
+      "selector": "$[?(@.foo == @.bar)]",
+      "document": [{"foo": 1, "bar": 2}, {"foo": 42, "bar": 42}, {"foo": 1, "bro": 1}, {}],
+      "values": [{"foo": 42, "bar": 42}, {}],
+      "paths": ["$[1]", "$[3]"],
+      "pointers": ["/1", "/3"]
     }
   ]
 }