Add new invocation context class. (#52)

* Add new invocation context class.

* Add changelog entry.

* Add unit tests for invocation context.

* Cleanup.

* Fix string constant.

.changes/unreleased/Features-20240201-104437.yaml

@@ -0,0 +1,6 @@
+kind: Features
+body: Added a new InvocationContext class for application context management.
+time: 2024-02-01T10:44:37.161298-05:00
+custom:
+  Author: peterallenwebb
+  Issue: "57"

dbt_common/context.py

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+from contextvars import ContextVar
+from typing import List, Mapping, Optional
+
+from dbt_common.constants import SECRET_ENV_PREFIX
+
+
+class InvocationContext:
+    def __init__(self, env: Mapping[str, str]):
+        self._env = env
+        self._env_secrets: Optional[List[str]] = None
+        # This class will also eventually manage the invocation_id, flags, event manager, etc.
+
+    @property
+    def env(self) -> Mapping[str, str]:
+        return self._env
+
+    @property
+    def env_secrets(self) -> List[str]:
+        if self._env_secrets is None:
+            self._env_secrets = [
+                v for k, v in self.env.items() if k.startswith(SECRET_ENV_PREFIX) and v.strip()
+            ]
+        return self._env_secrets
+
+
+_INVOCATION_CONTEXT_VAR: ContextVar[InvocationContext] = ContextVar("DBT_INVOCATION_CONTEXT_VAR")
+
+
+def set_invocation_context(env: Mapping[str, str]) -> None:
+    _INVOCATION_CONTEXT_VAR.set(InvocationContext(env))
+
+
+def get_invocation_context() -> InvocationContext:
+    ctx = _INVOCATION_CONTEXT_VAR.get()
+    return ctx

tests/unit/test_invocation_context.py

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+from dbt_common.constants import SECRET_ENV_PREFIX
+from dbt_common.context import InvocationContext
+
+
+def test_invocation_context_env():
+    test_env = {"VAR_1": "value1", "VAR_2": "value2"}
+    ic = InvocationContext(env=test_env)
+    assert ic.env == test_env
+
+
+def test_invocation_context_secrets():
+    test_env = {
+        f"{SECRET_ENV_PREFIX}_VAR_1": "secret1",
+        f"{SECRET_ENV_PREFIX}VAR_2": "secret2",
+        "NON_SECRET": "non-secret",
+        f"foo{SECRET_ENV_PREFIX}": "non-secret",
+    }
+    ic = InvocationContext(env=test_env)
+    assert set(ic.env_secrets) == set(["secret1", "secret2"])