`fabric/debug` module and `DebugStringConvertible` class

Summary:
This is a very first diff in a series of undefined length implementing React Native Shadow Tree infra in C++.
All Shadow Nodes, Props and etc. implements `DebugStringConvertible`.

Authored by shergin

Reviewed By: shergin

Differential Revision: D7163868

fbshipit-source-id: 9c001aa5bd0723f709a07b1833f512c51e3bec11

ReactCommon/fabric/BUCK

@@ -1,10 +1,5 @@
 load("@xplat//configurations/buck/apple:flag_defs.bzl", "get_debug_preprocessor_flags")
-load("//ReactNative:DEFS.bzl", "IS_OSS_BUILD", "rn_xplat_cxx_library", "APPLE_INSPECTOR_FLAGS")
-
-CXX_LIBRARY_COMPILER_FLAGS = [
-    "-std=c++14",
-    "-Wall",
-]
+load("//ReactNative:DEFS.bzl", "IS_OSS_BUILD", "react_native_xplat_target", "rn_xplat_cxx_library", "APPLE_INSPECTOR_FLAGS")
 
 APPLE_COMPILER_FLAGS = []
 
@@ -14,17 +9,19 @@ if not IS_OSS_BUILD:
 
 rn_xplat_cxx_library(
     name = "fabric",
-    srcs = glob(["**/*.cpp"]),
+    srcs = glob(["*.cpp"]),
     header_namespace = "",
     exported_headers = subdir_glob(
         [
-            ("", "**/*.h"),
+            ("", "*.h"),
         ],
         prefix = "fabric",
     ),
-    compiler_flags = CXX_LIBRARY_COMPILER_FLAGS + [
+    compiler_flags = [
         "-fexceptions",
         "-frtti",
+        "-std=c++14",
+        "-Wall",
     ],
     fbobjc_compiler_flags = APPLE_COMPILER_FLAGS,
     fbobjc_preprocessor_flags = get_debug_preprocessor_flags() + APPLE_INSPECTOR_FLAGS,
@@ -42,5 +39,6 @@ rn_xplat_cxx_library(
         "xplat//folly:memory",
         "xplat//folly:molly",
         "xplat//third-party/glog:glog",
+        react_native_xplat_target("fabric/debug:debug"),
     ],
 )

ReactCommon/fabric/debug/BUCK

@@ -0,0 +1,46 @@
+load("@xplat//configurations/buck/apple:flag_defs.bzl", "get_debug_preprocessor_flags")
+load("//ReactNative:DEFS.bzl", "IS_OSS_BUILD", "react_native_xplat_target", "rn_xplat_cxx_library", "APPLE_INSPECTOR_FLAGS")
+
+APPLE_COMPILER_FLAGS = []
+
+if not IS_OSS_BUILD:
+    load("@xplat//configurations/buck/apple:flag_defs.bzl", "get_static_library_ios_flags", "flags")
+    APPLE_COMPILER_FLAGS = flags.get_flag_value(get_static_library_ios_flags(), 'compiler_flags')
+
+rn_xplat_cxx_library(
+    name = "debug",
+    srcs = glob(
+        [
+            "**/*.cpp",
+        ],
+    ),
+    headers = glob(
+        [
+            "**/*.h",
+        ],
+    ),
+    header_namespace = "",
+    exported_headers = subdir_glob(
+        [
+            ("", "*.h"),
+        ],
+        prefix = "fabric/debug",
+    ),
+    compiler_flags = [
+        "-std=c++14",
+        "-Wall",
+        "-fexceptions",
+        "-frtti",
+    ],
+    fbobjc_compiler_flags = APPLE_COMPILER_FLAGS,
+    fbobjc_preprocessor_flags = get_debug_preprocessor_flags() + APPLE_INSPECTOR_FLAGS,
+    force_static = True,
+    preprocessor_flags = [
+        "-DLOG_TAG=\"ReactNative\"",
+        "-DWITH_FBSYSTRACE=1",
+    ],
+    visibility = ["PUBLIC"],
+    deps = [
+        "xplat//folly:headers_only",
+    ],
+)

ReactCommon/fabric/debug/DebugStringConvertible.cpp

@@ -0,0 +1,71 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "DebugStringConvertible.h"
+
+namespace facebook {
+namespace react {
+
+std::string DebugStringConvertible::getDebugChildrenDescription(int level) const {
+  std::string childrenString = "";
+
+  for (auto child : getDebugChildren()) {
+    childrenString += child->getDebugDescription(level + 1);
+  }
+
+  return childrenString;
+}
+
+std::string DebugStringConvertible::getDebugPropsDescription(int level) const {
+  std::string propsString = "";
+
+  for (auto prop : getDebugProps()) {
+    auto name = prop->getDebugName();
+    auto value = prop->getDebugValue();
+    auto children = prop->getDebugPropsDescription(level + 1);
+    auto valueAndChildren = value + (children.empty() ? "" : "(" + children + ")");
+    propsString += " " + name + (valueAndChildren.empty() ? "" : "=" + valueAndChildren);
+  }
+
+  if (!propsString.empty()) {
+    // Removing leading space character.
+    propsString.erase(propsString.begin());
+  }
+
+  return propsString;
+}
+
+std::string DebugStringConvertible::getDebugDescription(int level) const {
+  std::string nameString = getDebugName();
+  std::string valueString = getDebugValue();
+  std::string childrenString = getDebugChildrenDescription(level);
+  std::string propsString = getDebugPropsDescription(level);
+
+  return "<" + nameString +
+    (valueString.empty() ? "" : "=" + valueString) +
+    (propsString.empty() ? "" : " " + propsString) +
+    (childrenString.empty() ? "/>" : ">" + childrenString + "</" + nameString + ">");
+}
+
+std::string DebugStringConvertible::getDebugName() const {
+  return "Node";
+}
+
+std::string DebugStringConvertible::getDebugValue() const {
+  return "";
+}
+
+SharedDebugStringConvertibleList DebugStringConvertible::getDebugChildren() const {
+  return SharedDebugStringConvertibleList();
+}
+
+SharedDebugStringConvertibleList DebugStringConvertible::getDebugProps() const {
+  return SharedDebugStringConvertibleList();
+}
+
+} // namespace react
+} // namespace facebook

ReactCommon/fabric/debug/DebugStringConvertible.h

@@ -0,0 +1,59 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <string>
+#include <vector>
+
+namespace facebook {
+namespace react {
+
+class DebugStringConvertible;
+
+using SharedDebugStringConvertible = std::shared_ptr<const DebugStringConvertible>;
+using SharedDebugStringConvertibleList = std::vector<const SharedDebugStringConvertible>;
+
+// Abstract class describes conformance to DebugStringConvertible concept
+// and implements basic recursive debug string assembly algorithm.
+// Use this as a base class for providing a debugging textual representation
+// of your class.
+// TODO (#26770211): Clear up the naming.
+class DebugStringConvertible {
+
+public:
+  // Returns a name of the object.
+  // Default implementation returns "Node".
+  virtual std::string getDebugName() const;
+
+  // Returns a value assosiate with the object.
+  // Default implementation returns an empty string.
+  virtual std::string getDebugValue() const;
+
+  // Returns a list of `DebugStringConvertible` objects which can be considered
+  // as *children* of the object.
+  // Default implementation returns an empty list.
+  virtual SharedDebugStringConvertibleList getDebugChildren() const;
+
+  // Returns a list of `DebugStringConvertible` objects which can be considered
+  // as *properties* of the object.
+  // Default implementation returns an empty list.
+  virtual SharedDebugStringConvertibleList getDebugProps() const;
+
+  // Returns a string which represents the object in a human-readable way.
+  // Default implementation returns a description of the subtree
+  // rooted at this node, represented in XML-like format.
+  virtual std::string getDebugDescription(int level = 0) const;
+
+  // Do same as `getDebugDescription` but return only *children* and
+  // *properties* parts (which are used in `getDebugDescription`).
+  virtual std::string getDebugPropsDescription(int level = 0) const;
+  virtual std::string getDebugChildrenDescription(int level = 0) const;
+};
+
+} // namespace react
+} // namespace facebook

ReactCommon/fabric/debug/DebugStringConvertibleItem.cpp

@@ -0,0 +1,41 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "DebugStringConvertibleItem.h"
+
+namespace facebook {
+namespace react {
+
+DebugStringConvertibleItem::DebugStringConvertibleItem(
+  const std::string &name,
+  const std::string &value,
+  const SharedDebugStringConvertibleList &props,
+  const SharedDebugStringConvertibleList &children
+):
+  name_(name),
+  value_(value),
+  props_(props),
+  children_(children) {}
+
+std::string DebugStringConvertibleItem::getDebugName() const {
+  return name_;
+}
+
+std::string DebugStringConvertibleItem::getDebugValue() const {
+  return value_;
+}
+
+SharedDebugStringConvertibleList DebugStringConvertibleItem::getDebugProps() const {
+  return props_;
+}
+
+SharedDebugStringConvertibleList DebugStringConvertibleItem::getDebugChildren() const {
+  return children_;
+}
+
+} // namespace react
+} // namespace facebook

ReactCommon/fabric/debug/DebugStringConvertibleItem.h

@@ -0,0 +1,45 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <fabric/debug/DebugStringConvertible.h>
+
+namespace facebook {
+namespace react {
+
+// Trivial implementation of `DebugStringConvertible` abstract class
+// with a stored output; useful for assembling `DebugStringConvertible` values
+// in custom implementations of `getDebugChildren` and `getDebugProps`.
+class DebugStringConvertibleItem:
+  public DebugStringConvertible {
+
+public:
+  DebugStringConvertibleItem() = default;
+  DebugStringConvertibleItem(const DebugStringConvertibleItem &item) = default;
+
+  DebugStringConvertibleItem(
+    const std::string &name = "",
+    const std::string &value = "",
+    const SharedDebugStringConvertibleList &props = {},
+    const SharedDebugStringConvertibleList &children = {}
+  );
+
+  std::string getDebugName() const override;
+  std::string getDebugValue() const override;
+  SharedDebugStringConvertibleList getDebugChildren() const override;
+  SharedDebugStringConvertibleList getDebugProps() const override;
+
+private:
+  std::string name_;
+  std::string value_;
+  SharedDebugStringConvertibleList props_;
+  SharedDebugStringConvertibleList children_;
+};
+
+} // namespace react
+} // namespace facebook