access hydra config through ${hydra:key}

hydra/core/hydra_config.py

@@ -15,7 +15,7 @@ def set_config(self, cfg: DictConfig) -> None:
         assert cfg is not None
         OmegaConf.set_readonly(cfg.hydra, True)
         assert OmegaConf.get_type(cfg, "hydra") == HydraConf
-        self.cfg = cfg  # type: ignore
+        self.cfg = OmegaConf.masked_copy(cfg, "hydra")  # type: ignore
 
     @staticmethod
     def get() -> HydraConf:

hydra/core/utils.py

@@ -126,13 +126,15 @@ def get_valid_filename(s: str) -> str:
 
 
 def setup_globals() -> None:
-    try:
-        OmegaConf.register_resolver(
-            "now", lambda pattern: strftime(pattern, localtime())
-        )
-    except AssertionError:
-        # calling it again in no_workers mode will throw. safe to ignore.
-        pass
+    def register(name: str, f: Any):
+        try:
+            OmegaConf.register_resolver(name, f)
+        except AssertionError:
+            # calling it again in no_workers mode will throw. safe to ignore.
+            pass
+
+    register("now", lambda pattern: strftime(pattern, localtime()))
+    register("hydra", lambda path: OmegaConf.select(HydraConfig.get(), path))
 
 
 @dataclass

hydra/test_utils/configs/accessing_hydra_config.yaml

@@ -0,0 +1,3 @@
+cwd: ${hydra:runtime.cwd}
+job_name: ${hydra:job.name}
+config_name: ${hydra:job.config_name}

news/325.feature

@@ -0,0 +1 @@
+Hydra config can now be accessed through interpolation using ${hydra:key}, for example ${hydra:job.name}

tests/test_core_utils.py

@@ -0,0 +1,24 @@
+# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
+from omegaconf import OmegaConf, open_dict
+from typing import Any
+
+from hydra._internal.config_loader_impl import ConfigLoaderImpl
+from hydra._internal.utils import create_config_search_path
+from hydra.core import utils
+from hydra.core.hydra_config import HydraConfig
+
+
+def test_foo(restore_singletons: Any) -> Any:
+    utils.setup_globals()
+
+    config_loader = ConfigLoaderImpl(
+        config_search_path=create_config_search_path("pkg://hydra.test_utils.configs")
+    )
+    cfg = config_loader.load_configuration(
+        config_name="accessing_hydra_config", overrides=[]
+    )
+    HydraConfig.instance().set_config(cfg)
+    with open_dict(cfg):
+        del cfg["hydra"]
+    assert cfg.job_name == "UNKNOWN_NAME"
+    assert cfg.config_name == "accessing_hydra_config"

website/docs/configure_hydra/Intro.md

@@ -4,7 +4,9 @@ title: Overview
 sidebar_label: Introduction
 ---
 
-Many things in Hydra can be customized, this includes:
+Many things in Hydra can be customized. This includes:
+* Launcher configurations
+* Sweeper configuration
 * Logging configuration
 * Run and Multirun output directory patterns
 * Application help (--help and --hydra-help)
@@ -43,14 +45,24 @@ hydra:
 ```
 
 ## Runtime variables
-The following variables are populated at runtime.
-You can access them as config variables.
+The `hydra` package is deleted from your config when the function runs to reduce the amount of noise
+in the config passed to the function.  
+You can still access all config nodes in Hydra through the custom resolver `hydra`. 
+
+For example:
+```yaml
+config_name: ${hydra:job.config_name}
+```
+Pay close attention to the syntax: The resolver name is `hydra`, and the `key` is passed after the colon.
+
+The following variables are some of the variables populated at runtime.  
+You can see the full Hydra config using `--cfg hydra`:
 
 `hydra.job`:
 - *hydra.job.name* : Job name, defaults to python file name without suffix. can be overridden.
 - *hydra.job.override_dirname* : Pathname derived from the overrides for this job
 - *hydra.job.num* : job serial number in sweep
-- *hydra.job.id* : Job ID in the underlying jobs system (Slurm etc) 
+- *hydra.job.id* : Job ID in the underlying jobs system (SLURM etc) 
 
 `hydra.runtime`:
 - *hydra.runtime.version*: Hydra's version

website/docs/tutorials/basic/your_first_app/config_groups.md

@@ -41,7 +41,7 @@ Learn more about packages directive [here](/advanced/package_directive.md).
 
 ### Using config groups
 Since we moved all the configs into the `conf` directory, we need to tell Hydra where to find them using the `config_path` parameter.
-`config_path` is a directory relative to `my_app.py`.
+**`config_path` is a directory relative to `my_app.py`**.
 ```python title="my_app.py" {1}
 @hydra.main(config_path="conf")
 def my_app(cfg: DictConfig) -> None: