feat(jinja): add b64decode/b64encode builtin filters

docs/guides/configuration.md

@@ -170,6 +170,16 @@ The examples specify a Snowflake connection whose password is stored in an envir
           account: <account>
     ```
 
+    !!! tip "Base64-encoded secrets"
+
+        If a secret is distributed base64-encoded in a single environment variable (for example a BigQuery service-account key), pipe the variable through the built-in `b64decode` filter to decode it to text inline:
+
+        ```yaml
+        keyfile_json: {{ env_var('BIGQUERY_KEY_B64') | b64decode }}
+        ```
+
+        A matching `b64encode` filter is also available. Both return UTF-8 text, so they are intended for string/JSON secrets rather than arbitrary binary data.
+
 === "Python"
 
     Python accesses environment variables via the `os` library's `environ` dictionary.

sqlmesh/utils/jinja.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import base64
 import importlib
 import json
 import re
@@ -28,11 +29,40 @@
 SQLMESH_JINJA_PACKAGE = "sqlmesh.utils.jinja"
 
 
+def b64decode(value: t.Union[str, bytes]) -> str:
+    """Decode a base64-encoded value and return it as UTF-8 text.
+
+    Intended for base64-encoded string/JSON secrets (for example a service-account
+    key stored in an environment variable), not arbitrary binary payloads.
+    """
+    decoded = value.encode("utf-8") if isinstance(value, str) else value
+    return base64.b64decode(decoded).decode("utf-8")
+
+
+def b64encode(value: t.Union[str, bytes]) -> str:
+    """Base64-encode a value and return the encoding as UTF-8 text.
+
+    The input is treated as UTF-8 text, mirroring ``b64decode``; it is intended for
+    string/JSON secrets rather than arbitrary binary payloads.
+    """
+    encoded = value.encode("utf-8") if isinstance(value, str) else value
+    return base64.b64encode(encoded).decode("utf-8")
+
+
+def create_builtin_filters() -> t.Dict[str, t.Callable]:
+    return {
+        "b64decode": b64decode,
+        "b64encode": b64encode,
+    }
+
+
 def environment(**kwargs: t.Any) -> Environment:
     extensions = kwargs.pop("extensions", [])
     extensions.append("jinja2.ext.do")
     extensions.append("jinja2.ext.loopcontrols")
-    return Environment(extensions=extensions, **kwargs)
+    env = Environment(extensions=extensions, **kwargs)
+    env.filters.update(create_builtin_filters())
+    return env
 
 
 ENVIRONMENT = environment()

tests/utils/test_jinja.py

@@ -1,6 +1,8 @@
 from __future__ import annotations
 
-from sqlmesh.utils import AttributeDict
+from base64 import b64encode
+
+from sqlmesh.utils import AttributeDict, yaml
 from sqlmesh.utils.jinja import (
     ENVIRONMENT,
     JinjaMacroRegistry,
@@ -329,3 +331,25 @@ def test_macro_registry_to_expressions_sorted():
         == "refs = {'orders': {'database': 'jaffle_shop', 'nested_list': ['a', 'b', 'c'], 'schema': 'main'}, 'payments': {'database': 'jaffle_shop', 'nested': {'baz': 'bing', 'foo': 'bar'}, 'schema': 'main'}}\n"
         "sources = {}"
     )
+
+
+def test_builtin_base64_filters():
+    encoded = b64encode(b"secret").decode("utf-8")
+
+    env = JinjaMacroRegistry().build_environment()
+    assert env.from_string("{{ value | b64decode }}").render(value=encoded) == "secret"
+    assert env.from_string("{{ 'secret' | b64encode }}").render() == encoded
+    assert env.from_string("{{ 'secret' | b64encode | b64decode }}").render() == "secret"
+
+    # The same filters are available when rendering Jinja in config YAML files.
+    config = yaml.load(f'env_vars:\n  TOKEN: "{{{{ "{encoded}" | b64decode }}}}"')
+    assert config == {"env_vars": {"TOKEN": "secret"}}
+
+
+def test_builtin_b64decode_with_env_var(monkeypatch):
+    # Real-world use case: a base64-encoded secret stored in an environment variable
+    # is decoded inline in config YAML via env_var(...) piped through b64decode.
+    monkeypatch.setenv("SNOWFLAKE_PW_B64", b64encode(b"super-secret-pw").decode("utf-8"))
+
+    config = yaml.load("password: \"{{ env_var('SNOWFLAKE_PW_B64') | b64decode }}\"")
+    assert config == {"password": "super-secret-pw"}