Warn about importing gdal directly

Author: Joonalai

README.md

@@ -33,6 +33,8 @@ Just call `flake8 .` in your package or `flake your.py`.
 * `QGS103`: Don't use from-imports from PyQt directly ([example](#QGS103))
 * `QGS104`: Don't use imports from PyQt directly ([example](#QGS104))
 * `QGS105`: Don't pass QgisInterface as an argument ([example](#QGS105))
+* `QGS106`: Don't import gdal directly, import if from osgeo package ([example](#QGS106))
+
 
 
 You might have good reasons to ignore some rules.
@@ -108,3 +110,14 @@ def some_function(somearg):
 def classFactory(iface):
     # preferably do not pass the iface to plugin
 ```
+
+### QGS106
+
+```python
+# Bad
+import gdal
+import ogr
+
+# Good
+from osgeo import gdal
+```

flake8_qgis/flake8_qgis.py

@@ -26,6 +26,7 @@
     "QGS105 Do not pass iface (QgisInterface) as an argument, "
     "instead import it: 'from qgs.utils import iface'"
 )
+QGS106 = "QGS106 Use 'from osgeo import {members}' " "instead of 'import {members}'"
 
 
 def _get_qgs101_and_103(
@@ -139,6 +140,20 @@ def _get_qgs105(node: ast.FunctionDef) -> List[Tuple[int, int, str]]:
     return errors
 
 
+def _get_qgs106(node: ast.Import) -> List[Tuple[int, int, str]]:
+    errors: List[Tuple[int, int, str]] = []
+    for alias in node.names:
+        if alias.name in ("gdal", "ogr"):
+            errors.append(
+                (
+                    node.lineno,
+                    node.col_offset,
+                    QGS106.format(members=alias.name),
+                )
+            )
+    return errors
+
+
 class Visitor(ast.NodeVisitor):
     def __init__(self) -> None:
         self.errors: List[Tuple[int, int, str]] = []
@@ -151,6 +166,7 @@ def visit_ImportFrom(self, node: ast.ImportFrom) -> Any:  # noqa N802
     def visit_Import(self, node: Import) -> Any:  # noqa N802
         self.errors += _get_qgs102(node)
         self.errors += _get_qgs104(node)
+        self.errors += _get_qgs106(node)
         self.generic_visit(node)
 
     def visit_FunctionDef(self, node: FunctionDef) -> Any:  # noqa N802

tests/test_flake8_qgis.py

@@ -151,3 +151,18 @@ def some_method(somearg, iface):
         "QGS105 Do not pass iface (QgisInterface) as an argument, instead import "
         "it: 'from qgs.utils import iface'"
     )
+
+
+def test_QGS106_pass():
+    ret = _results("from osgeo import gdal")
+    ret = ret.union(_results("from osgeo import ogr"))
+    assert ret == set()
+
+
+def test_QGS106():
+    ret = _results("import gdal")
+    ret = ret.union(_results("import ogr"))
+    assert ret == {
+        "1:0 QGS106 Use 'from osgeo import gdal' instead of 'import gdal'",
+        "1:0 QGS106 Use 'from osgeo import ogr' instead of 'import ogr'",
+    }