First commit, extracted from BandSquare's internal code

.gitignore

@@ -0,0 +1,14 @@
+/target
+/classes
+/checkouts
+pom.xml
+pom.xml.asc
+*.jar
+*.class
+/.lein-*
+/.nrepl-port
+.hgignore
+.hg/
+
+*.iml
+.idea

CHANGELOG.md

@@ -0,0 +1,10 @@
+# Change Log
+All notable changes to this project will be documented in this file. This change log follows the conventions of [keepachangelog.com](http://keepachangelog.com/).
+
+## [Unreleased]
+
+## [0.0.1-alpha] - 2018-03-27
+### Added
+- Basic implementation and tests based on BandSquare's internal code, supports asynchronous and tabular resolvers.
+
+[Unreleased]: https://github.com/your-name/d2q/compare/0.1.1-alpha...HEAD

LICENSE

@@ -0,0 +1,7 @@
+Copyright 2018 BandSquare and contributors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

@@ -0,0 +1,15 @@
+# d2q
+
+A Clojure library which provides a generic, expressive, efficient way of implementing query servers for demand-driven languages such as GraphQL.
+
+**Project status:** less than alpha, open-sourced to allow for development outside of the company. Do not use yet, as major breaking changes will occur soon. 
+
+## Usage
+
+TBD
+
+## License
+
+Copyright © 2018 BandSquare and contributors
+
+Distributed under the MIT license.

doc/intro.md

@@ -0,0 +1,3 @@
+# Introduction to d2q
+
+TODO: write [great documentation](http://jacobian.org/writing/what-to-write/)

project.clj

@@ -0,0 +1,11 @@
+(defproject bandsquare/d2q "0.0.1-SNAPSHOT"
+  :description "An expressive toolkit for building efficient GraphQL-like query servers"
+  :url "https://github.com/bandsquare/d2q"
+  :license {:name "MIT License"
+            :url "https://opensource.org/licenses/MIT"}
+  :dependencies [[org.clojure/clojure "1.8.0"]
+                 [manifold "0.1.6"]]
+  :profiles
+  {:dev
+   {:dependencies
+    [[midje "1.7.0"]]}})

src/d2q/api.clj

@@ -0,0 +1,95 @@
+(ns d2q.api
+  "Demand-driven querying à la GraphQL / Datomic Pull"
+  (:require [clojure.walk]
+            [manifold.deferred :as mfd]
+            [d2q.impl.utils :as impl.utils]
+            [d2q.impl]))
+
+;; TODO improvements (Val, 15 Mar 2018)
+;; 1. √ Remove specific authorization model - replace by a query-level resolution step
+;; 2. Subquery preview in resolvers? May require to change the format of resolvers.
+;; 3. Partial errors => resolvers return a map with {:data :errors} key
+;; 4. Maybe skip the normalization of query - should be done by the caller
+;; 5. Mutual recursion (requires to change the query format)
+;; 6. Source mapping - keep track of (reversed) query-path and data-path
+;; 7. Maybe faster processing via records ?
+
+;; IMPROVEMENT maybe we can let the client express than some field is required etc. (Val, 30 May 2017)
+(defn normalize-query-field
+  [f]
+  (as-> f f
+    (if (map? f)
+      f
+      {:d2q.fcall/field f})
+
+    (update f
+      :d2q.fcall/key
+      #(or % (:d2q.fcall/field f)))
+
+    (if-let [nested (:d2q.fcall/nested f)]
+      (assoc f :d2q.fcall/nested (into [] (map normalize-query-field) nested))
+      f)))
+
+(defn normalize-query
+  [pull-spec]
+  (into [] (map normalize-query-field) pull-spec))
+
+(defn query-engine
+  "Compiles tabular field resolvers + fields specs + entity-transformation fn to a function for computing demand-driven queries.
+  The returned function has signature [qctx, q, obj] -> Deferred<query-result>"
+  [tabular-resolvers
+   fields
+   transform-entities-fn                                    ;; TODO find a better name for this step (Val, 17 Mar 2018)
+   ]
+  (let [eng (d2q.impl/engine tabular-resolvers fields transform-entities-fn)]
+    (fn query [qctx q obj]
+      (let [query (normalize-query q)]
+        (d2q.impl/query eng qctx query obj)))))
+
+;; ------------------------------------------------------------------------------
+;; Generalization of the Fields-resolver model
+
+(defn tabular-resolver-from-field-resolvers
+  [tr-name fields]
+  {:d2q.resolver/name tr-name
+   :d2q.resolver/compute
+   (let [frs-by-field-name (impl.utils/index-and-map-by
+                             :d2q.field/name
+                             :bs.d2q.field/compute
+                             fields)]
+     (fn resolve-table [qctx f+args o+is]
+       (mfd/future
+         (let [fs (->> f+args
+                    (mapv (fn [[k field-name args]]
+                            (let [compute-fn (or
+                                               (frs-by-field-name field-name)
+                                               (throw (ex-info
+                                                        (str "No field with name " (pr-str field-name)
+                                                          " is supported by tabular resolver " (pr-str tr-name))
+                                                        {:d2q.fcall/field field-name
+                                                         :d2q.fcall/args args
+                                                         :d2q.resolver/name tr-name})))]
+                              [k compute-fn args field-name]))))]
+           (into []
+             (remove nil?)
+             (for [[obj i] o+is
+                   [k compute-fn args field-name] fs]
+               (let [v (try
+                         ;; TODO use deps argument ? (Val, 16 Nov 2017)
+                         (compute-fn qctx obj nil args)
+                         (catch Throwable err
+                           (throw
+                             (ex-info
+                               (str
+                                 "Field Resolver for key " (pr-str (:d2q.fcall/key k))
+                                 " failed with " (pr-str (type err))
+                                 " : " (.getMessage err))
+                               (merge
+                                 {:q-field {:d2q.fcall/field field-name
+                                            :d2q.fcall/key k
+                                            :d2q.fcall/args args}
+                                  :d2q.error/type :d2q.error.type/field-resolver-failed-to-compute}
+                                 (ex-data err))
+                               err))))]
+                 (when (some? v)
+                   [i k v]))))))))})