From 8909b8313171e37e42279e772ced657aed89ce66 Mon Sep 17 00:00:00 2001
From: BlackPhantomCoder <shevzovdima@yandex.com>
Date: Sat, 26 Sep 2026 22:02:52 +0300
Subject: [PATCH] _yaml.pyx: Handle OSError when loading file

When an error occurs while opening or reading a file in `load`, the exception type contract is violated, and various `bst` commands report an error with a stack trace. Several examples have been added to the tests.
---
 src/buildstream/_yaml.pyx     |  3 +++
 src/buildstream/exceptions.py |  3 +++
 tests/internals/loader.py     | 22 ++++++++++++++++++++++
 3 files changed, 28 insertions(+)

diff --git a/src/buildstream/_yaml.pyx b/src/buildstream/_yaml.pyx
index 0097e1e74..a2d29496a 100644
--- a/src/buildstream/_yaml.pyx
+++ b/src/buildstream/_yaml.pyx
@@ -284,6 +284,9 @@ cpdef MappingNode load(str filename, str shortname, bint copy_tree=False, object
     except IsADirectoryError as e:
         raise LoadError("{} is a directory".format(filename),
                         LoadErrorReason.LOADING_DIRECTORY) from e
+    except OSError as e:
+         raise LoadError("Failed to load file at {}: {}".format(filename, e.strerror),
+                        LoadErrorReason.LOAD_FAILED) from e
     except LoadError as e:
         raise LoadError("{}: {}".format(displayname, e), e.reason) from e
 
diff --git a/src/buildstream/exceptions.py b/src/buildstream/exceptions.py
index 418e51eda..238e477ad 100644
--- a/src/buildstream/exceptions.py
+++ b/src/buildstream/exceptions.py
@@ -160,3 +160,6 @@ class LoadErrorReason(Enum):
     """
     Thee source provenance attribute specified was not defined in the project config
     """
+
+    LOAD_FAILED = 30
+    """Failed to load a yaml file due to some error"""
diff --git a/tests/internals/loader.py b/tests/internals/loader.py
index 47c5bc691..d29896def 100644
--- a/tests/internals/loader.py
+++ b/tests/internals/loader.py
@@ -110,3 +110,25 @@ def test_invalid_directory_load(datafiles):
         loader.load(["element.bst"])
 
     assert exc.value.reason == LoadErrorReason.LOADING_DIRECTORY
+
+
+@pytest.mark.datafiles(os.path.join(DATA_DIR, "onefile"))
+def test_invalid_nested_file_path(datafiles):
+
+    basedir = str(datafiles)
+    with make_loader(basedir) as loader, pytest.raises(LoadError) as exc:
+        loader.load(["elements/onefile.bst/onefile.bst"])
+
+    assert exc.value.reason == LoadErrorReason.LOAD_FAILED
+
+
+@pytest.mark.datafiles(os.path.join(DATA_DIR, "onefile"))
+def test_fail_load_open_error(datafiles):
+
+    basedir = str(datafiles)
+    # remove read prermission
+    os.chmod(f"{basedir}/elements/onefile.bst", 0o333)
+    with make_loader(basedir) as loader, pytest.raises(LoadError) as exc:
+        loader.load(["elements/onefile.bst"])
+
+    assert exc.value.reason == LoadErrorReason.LOAD_FAILED