Stop python-dotenv warning about flexmeasures.cfg on startup

documentation/changelog.rst

@@ -18,6 +18,8 @@ Infrastructure / Support
 
 Bugfixes
 -----------
+* Stop warning on startup that python-dotenv could not parse a statement in ``flexmeasures.cfg``, which happened in every Docker container since v1.1.0 [see `PR #2845 <https://www.github.com/FlexMeasures/flexmeasures/pull/2845>`_]
+
 * Apply storage losses to the starting stock of a state of charge shared by several devices, so its scheduled state of charge no longer drifts above the one the scheduler planned with [see `PR #2838 <https://www.github.com/FlexMeasures/flexmeasures/pull/2838>`_]
 
 * Hovering anywhere over a session in the Charge Points chart shows its tooltip again, listing all of the session's timestamps, as it did before the move to ECharts, without highlighting another charger's session; also, a chart's tooltip no longer shows a point from a neighbouring subplot [see `PR #2829 <https://www.github.com/FlexMeasures/flexmeasures/pull/2829>`_]

flexmeasures/ui/static/openapi-specs.json

@@ -7,7 +7,7 @@
     },
     "termsOfService": null,
     "title": "FlexMeasures",
-    "version": "1.1.0"
+    "version": "1.1.1"
   },
   "externalDocs": {
     "description": "FlexMeasures runs on the open source FlexMeasures technology. Read the docs here.",

flexmeasures/utils/config_utils.py

@@ -4,6 +4,7 @@
 
 from __future__ import annotations
 
+import ast
 import os
 import re
 import sys
@@ -15,7 +16,6 @@
 from flask import Flask
 from inflection import camelize
 import isodate
-from dotenv import dotenv_values
 import pandas as pd
 
 from flexmeasures.utils.config_defaults import (
@@ -80,14 +80,12 @@ def get_flexmeasures_env(app, cfg_location) -> str | None:
     """
     flexmeasures_env: str | None = DefaultConfig.FLEXMEASURES_ENV_DEFAULT
 
-    cfg_config = dotenv_values(cfg_location)
-
     if app.testing:
         flexmeasures_env = "testing"
     elif os.getenv("FLEXMEASURES_ENV", None):
         flexmeasures_env = os.getenv("FLEXMEASURES_ENV", None)
-    elif cfg_config.get("FLEXMEASURES_ENV", None):
-        flexmeasures_env = cfg_config.get("FLEXMEASURES_ENV", None)
+    elif cfg_env := read_flexmeasures_env_from_cfg(cfg_location):
+        flexmeasures_env = cfg_env
     elif os.getenv("FLASK_ENV", None):
         flexmeasures_env = os.getenv("FLASK_ENV", None)
         app.logger.warning(
@@ -98,6 +96,37 @@ def get_flexmeasures_env(app, cfg_location) -> str | None:
     return flexmeasures_env or None
 
 
+def read_flexmeasures_env_from_cfg(cfg_location: str | None) -> str | None:
+    """Look up the FLEXMEASURES_ENV that a flexmeasures.cfg file sets, without running the file.
+
+    The file is Python, so it is parsed as Python, rather than as a dotenv file,
+    which made python-dotenv warn about every line that is not a plain assignment, such as an import.
+    Only a top-level assignment of a string literal counts; the last one wins, as it would when the file runs.
+    A missing or unparsable file sets nothing here; loading the config reports what is wrong with it.
+    """
+    if cfg_location is None or not os.path.isfile(cfg_location):
+        return None
+    try:
+        tree = ast.parse(Path(cfg_location).read_text(), filename=cfg_location)
+    except (OSError, SyntaxError, ValueError):
+        return None
+    flexmeasures_env = None
+    for node in tree.body:
+        if isinstance(node, ast.Assign):
+            targets = node.targets
+        elif isinstance(node, ast.AnnAssign):
+            targets = [node.target]
+        else:
+            continue
+        if not any(
+            isinstance(t, ast.Name) and t.id == "FLEXMEASURES_ENV" for t in targets
+        ):
+            continue
+        if isinstance(node.value, ast.Constant) and isinstance(node.value.value, str):
+            flexmeasures_env = node.value.value
+    return flexmeasures_env
+
+
 def find_flexmeasures_cfg() -> str | None:
     """
     Try to find a flexmeasures.cfg file in the home or instance directories.

flexmeasures/utils/tests/test_config_utils.py

@@ -1,3 +1,4 @@
+import logging
 from datetime import timedelta
 
 import pytest
@@ -306,3 +307,56 @@ def test_configure_logging_keeps_loggers_that_already_exist(monkeypatch):
     finally:
         root.handlers[:] = root_handlers
         root.setLevel(root_level)
+
+
+def test_flexmeasures_env_from_a_python_cfg_raises_no_dotenv_warning(
+    tmp_path, monkeypatch, caplog
+):
+    """A flexmeasures.cfg is Python, so an import on its first line is fine, and should not set off python-dotenv's parse warning."""
+    cfg = tmp_path / "flexmeasures.cfg"
+    cfg.write_text(
+        "from datetime import timedelta\n"
+        "\n"
+        'FLEXMEASURES_ENV = "staging"\n'
+        "FLEXMEASURES_PLANNING_HORIZON = timedelta(days=2)\n"
+        "FLEXMEASURES_PLUGINS = [\n"
+        '    "/app/plugin",\n'
+        "]\n"
+    )
+    monkeypatch.delenv("FLEXMEASURES_ENV", raising=False)
+    monkeypatch.delenv("FLASK_ENV", raising=False)
+    app = Flask("flexmeasures-test")
+
+    with caplog.at_level(logging.DEBUG):
+        assert config_utils.get_flexmeasures_env(app, str(cfg)) == "staging"
+    assert not [r for r in caplog.records if r.name.startswith("dotenv")]
+
+
+@pytest.mark.parametrize(
+    "content, expected",
+    [
+        ('FLEXMEASURES_ENV = "production"\n', "production"),
+        ("FLEXMEASURES_ENV: str = 'staging'\n", "staging"),
+        # The last assignment wins, as it does when the file runs.
+        (
+            'FLEXMEASURES_ENV = "staging"\nFLEXMEASURES_ENV = "production"\n',
+            "production",
+        ),
+        # Only a string literal counts: an expression is not evaluated, and is not mistaken for a string.
+        ('import os\nFLEXMEASURES_ENV = os.environ.get("X", "staging")\n', None),
+        ("SQLALCHEMY_DATABASE_URI = 'postgresql://x'\n", None),
+        ("this is not python\n", None),
+    ],
+)
+def test_read_flexmeasures_env_from_cfg(tmp_path, content, expected):
+    cfg = tmp_path / "flexmeasures.cfg"
+    cfg.write_text(content)
+    assert config_utils.read_flexmeasures_env_from_cfg(str(cfg)) == expected
+
+
+def test_read_flexmeasures_env_from_missing_cfg(tmp_path):
+    assert config_utils.read_flexmeasures_env_from_cfg(None) is None
+    assert (
+        config_utils.read_flexmeasures_env_from_cfg(str(tmp_path / "missing.cfg"))
+        is None
+    )