Extended Interpolation of Values with "${this}" pattern // Resolve #3953

HISTORY.rst

@@ -53,6 +53,11 @@ PlatformIO Core 5
   - Added a new build variable (``COMPILATIONDB_INCLUDE_TOOLCHAIN``) to include toolchain paths in the compilation database (`issue #3735 <https://github.com/platformio/platformio-core/issues/3735>`_)
   - Changed default path for compilation database `compile_commands.json <https://docs.platformio.org/en/latest/integration/compile_commands.html>`__ to the project root
 
+* **Project Configuration**
+
+  - Extended `Interpolation of Values <https://docs.platformio.org/en/latest/projectconf/interpolation.html>`__  with ``${this}`` pattern (`issue #3953 <https://github.com/platformio/platformio-core/issues/3953>`_)
+  - Embed environment name of the current section in the `"platformio.ini" <https://docs.platformio.org/en/latest/projectconf.html>`__ configuration file using ``${this.__env__}`` pattern
+
 * **Miscellaneous**
 
   - Improved PIO Remote setup on credit-card sized computers (Raspberry Pi, BeagleBon, etc) (`issue #3865 <https://github.com/platformio/platformio-core/issues/3865>`_)

platformio/project/config.py

@@ -254,7 +254,7 @@ class ProjectConfigBase(object):
                 value = (
                     default if default != MISSING else self._parser.get(section, option)
                 )
-            return self._expand_interpolations(value)
+            return self._expand_interpolations(section, value)
 
         if option_meta.sysenvvar:
             envvar_value = os.getenv(option_meta.sysenvvar)
@@ -277,21 +277,31 @@ class ProjectConfigBase(object):
         if value == MISSING:
             return None
 
-        return self._expand_interpolations(value)
+        return self._expand_interpolations(section, value)
 
-    def _expand_interpolations(self, value):
+    def _expand_interpolations(self, parent_section, value):
         if (
             not value
             or not isinstance(value, string_types)
             or not all(["${" in value, "}" in value])
         ):
             return value
-        return self.VARTPL_RE.sub(self._re_interpolation_handler, value)
+        return self.VARTPL_RE.sub(
+            lambda match: self._re_interpolation_handler(parent_section, match), value
+        )
 
-    def _re_interpolation_handler(self, match):
+    def _re_interpolation_handler(self, parent_section, match):
         section, option = match.group(1), match.group(2)
+        # handle system environment variables
         if section == "sysenv":
             return os.getenv(option)
+        # handle ${this.*}
+        if section == "this":
+            section = parent_section
+            if option == "__env__":
+                assert parent_section.startswith("env:")
+                return parent_section[4:]
+        # handle nested calls
         try:
             value = self.getraw(section, option)
         except RecursionError:

tests/project/test_config.py

@@ -17,6 +17,7 @@
 import configparser
 import os
 import sys
+from pathlib import Path
 
 import pytest
 
@@ -578,3 +579,21 @@ core_dir = ~/.pio
             fs.rmtree(win_core_root_dir)
     except PermissionError:
         pass
+
+
+def test_this(tmp_path: Path):
+    project_conf = tmp_path / "platformio.ini"
+    project_conf.write_text(
+        """
+[common]
+board = uno
+
+[env:myenv]
+extends = common
+build_flags = -D${this.__env__}
+custom_option = ${this.board}
+    """
+    )
+    config = ProjectConfig(str(project_conf))
+    assert config.get("env:myenv", "custom_option") == "uno"
+    assert config.get("env:myenv", "build_flags") == ["-Dmyenv"]