fix #10422: add test for env_var casing on windows

.gitignore

@@ -105,3 +105,4 @@ venv/
 
 # poetry
 poetry.lock
+.venv/

core/dbt/context/base.py

@@ -314,6 +314,13 @@ def env_var(self, var: str, default: Optional[str] = None) -> str:
         env = get_invocation_context().env
         if var in env:
             return_value = env[var]
+        elif os.name == "nt":
+            # Windows env vars are not case-sensitive
+            # So if there isn't an exact match, try a case-insensitive match
+            for key in env:
+                if var.casefold() == key.casefold():
+                    return_value = env[key]
+                    break
         elif default is not None:
             return_value = default
 

tests/functional/context_methods/test_env_vars_casing.py

@@ -0,0 +1,64 @@
+import os
+
+import pytest
+
+from dbt.tests.util import run_dbt
+
+context_sql = """
+
+{{
+    config(
+        materialized='table'
+    )
+}}
+
+select
+    '{{ env_var("local_user", "") }}' as lowercase,
+    '{{ env_var("LOCAL_USER", "") }}' as uppercase,
+    '{{ env_var("lOcAl_UsEr", "") }}' as mixedcase
+"""
+
+
+class TestEnvVars:
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {"context.sql": context_sql}
+
+    @pytest.fixture(scope="class", autouse=True)
+    def setup(self):
+        os.environ["local_user"] = "dan"
+        yield
+        del os.environ["local_user"]
+
+    def get_ctx_vars(self, project):
+        fields = [
+            "lowercase",
+            "uppercase",
+            "mixedcase",
+        ]
+        field_list = ", ".join(['"{}"'.format(f) for f in fields])
+        query = "select {field_list} from {schema}.context".format(
+            field_list=field_list, schema=project.test_schema
+        )
+        vals = project.run_sql(query, fetch="all")
+        ctx = dict([(k, v) for (k, v) in zip(fields, vals[0])])
+        return ctx
+
+    def test_env_vars(
+        self,
+        project,
+    ):
+        results = run_dbt(["run"])
+        assert len(results) == 1
+        ctx = self.get_ctx_vars(project)
+
+        assert ctx["lowercase"] == "dan"
+
+        # Windows env-vars are not case-sensitive, but Linux/macOS ones are
+        # So on Windows, the uppercase and mixedcase vars should also resolve to "dan"
+        if os.name == "nt":
+            assert ctx["uppercase"] == "dan"
+            assert ctx["mixedcase"] == "dan"
+        else:
+            assert ctx["uppercase"] == ""
+            assert ctx["mixedcase"] == ""