fix: compare the whole value in env2bool

dvc/utils/__init__.py

@@ -237,14 +237,19 @@ def as_posix(path: str) -> str:
     return path.replace(ntpath.sep, posixpath.sep)
 
 
+TRUTHY_VALUES = frozenset({"1", "y", "yes", "true"})
+
+
 def env2bool(var, undefined=False):
     """
     undefined: return value if env var is unset
     """
-    var = os.getenv(var, None)
-    if var is None:
+    value = os.getenv(var, None)
+    if value is None:
         return undefined
-    return bool(re.search("1|y|yes|true", var, flags=re.IGNORECASE))
+    # Compare the whole value: a substring search treats any value that merely
+    # contains "1" or "y" (e.g. "deny", "only", "10") as true.
+    return value.strip().lower() in TRUTHY_VALUES
 
 
 def resolve_output(inp: str, out: Optional[str], force=False) -> str:

tests/unit/utils/test_env2bool.py

@@ -0,0 +1,31 @@
+import pytest
+
+from dvc.utils import env2bool
+
+VAR = "DVC_TEST_ENV2BOOL"
+
+
+def test_unset_returns_undefined(monkeypatch):
+    monkeypatch.delenv(VAR, raising=False)
+    assert env2bool(VAR) is False
+    assert env2bool(VAR, undefined=True) is True
+
+
+@pytest.mark.parametrize("value", ["1", "y", "yes", "true", "TRUE", "Yes", " true "])
+def test_truthy_values(monkeypatch, value):
+    monkeypatch.setenv(VAR, value)
+    assert env2bool(VAR) is True
+
+
+@pytest.mark.parametrize("value", ["0", "n", "no", "false", "off", ""])
+def test_falsy_values(monkeypatch, value):
+    monkeypatch.setenv(VAR, value)
+    assert env2bool(VAR) is False
+
+
+@pytest.mark.parametrize("value", ["deny", "only", "anything", "my-value", "10", "1a"])
+def test_values_merely_containing_a_truthy_token_are_false(monkeypatch, value):
+    # The value is compared as a whole: a substring search would treat anything
+    # containing "1" or "y" as true, so "deny" and "10" would enable a flag.
+    monkeypatch.setenv(VAR, value)
+    assert env2bool(VAR) is False