Automatically enable LDF dependency chain+ mode (evaluates C/C++ Preprocessor conditional syntax) for Arduino library when “library.properties” has “depends” field // Resolve #3607

HISTORY.rst

@@ -35,6 +35,7 @@ PlatformIO Core 4
 * Added a new ``-e, --environment`` option to `platformio project init <https://docs.platformio.org/page/core/userguide/project/cmd_init.html#cmdoption-platformio-project-init-e>`__ command that helps to update a PlatformIO project using existing environment
 * Dump data intended for IDE extensions/plugins using a new `platformio project idedata <https://docs.platformio.org/page/core/userguide/project/cmd_idedata.html>`__ command
 * Do not generate ".travis.yml" for a new project, let the user have a choice
+* Automatically enable LDF dependency `chain+ mode (evaluates C/C++ Preprocessor conditional syntax) <https://docs.platformio.org/page/librarymanager/ldf.html#dependency-finder-mode>`__ for Arduino library when "library.property" has "depends" field (`issue #3607 <https://github.com/platformio/platformio-core/issues/3607>`_)
 * Fixed an issue with PIO Unit Testing when running multiple environments (`issue #3523 <https://github.com/platformio/platformio-core/issues/3523>`_)
 * Fixed an issue with improper processing of source files added via multiple Build Middlewares (`issue #3531 <https://github.com/platformio/platformio-core/issues/3531>`_)
 * Fixed an issue with ``clean`` target on Windows when project and build directories are located on different logical drives (`issue #3542 <https://github.com/platformio/platformio-core/issues/3542>`_)

platformio/builder/tools/piolib.py

@@ -507,6 +507,26 @@ class ArduinoLibBuilder(LibBuilderBase):
                 src_filter.append("+<utility%s*.%s>" % (sep, ext))
         return src_filter
 
+    @property
+    def dependencies(self):
+        # do not include automatically all libraries for build
+        # chain+ will decide later
+        return None
+
+    @property
+    def lib_ldf_mode(self):
+        if not self._manifest.get("dependencies"):
+            return LibBuilderBase.lib_ldf_mode.fget(self)
+        missing = object()
+        global_value = self.env.GetProjectConfig().getraw(
+            "env:" + self.env["PIOENV"], "lib_ldf_mode", missing
+        )
+        if global_value != missing:
+            return LibBuilderBase.lib_ldf_mode.fget(self)
+        # automatically enable C++ Preprocessing in runtime
+        # (Arduino IDE has this behavior)
+        return "chain+"
+
     def is_frameworks_compatible(self, frameworks):
         return util.items_in_list(frameworks, ["arduino", "energia"])