From 392c39ae845d37f503f695b2c316a45bef7ae786 Mon Sep 17 00:00:00 2001
From: Owen W. Taylor <otaylor@fishsoup.net>
Date: Nov 10 2023 18:32:40 +0000
Subject: flatpak_builder: error out cleanly on files in /usr/etc


According to comments in the code, we were meant to be dropping files
in /usr/etc (which conflicts with /etc with the Flatpak runtime files/
layer), but that wasn't actually implemented correctly.

Since files in /usr/etc typically reflect a packaging bug, error out
with a clean error message instead.

---

diff --git a/flatpak_module_tools/flatpak_builder.py b/flatpak_module_tools/flatpak_builder.py
index 5f32fbe..fe6c650 100644
--- a/flatpak_module_tools/flatpak_builder.py
+++ b/flatpak_module_tools/flatpak_builder.py
@@ -529,6 +529,11 @@ class PackageFlatpakSourceInfo(BaseFlatpakSourceInfo):
         return list(components)
 
 
+class FileMappingError(Exception):
+    def __str__(self):
+        return f"{self.args[1]}: {self.args[0]}"
+
+
 class FlatpakBuilder:
     def __init__(
             self, source: BaseFlatpakSourceInfo, workdir, root,
@@ -602,11 +607,17 @@ class FlatpakBuilder:
             for source, target, is_exact_match in patterns:
                 if is_exact_match:
                     if source == path:
-                        return target
+                        if isinstance(target, FileMappingError):
+                            raise FileMappingError(target.args[0], path)
+                        else:
+                            return target
                 else:
                     m = source.match(path)
                     if m:
-                        return os.path.join(target, m.group(1))
+                        if isinstance(target, FileMappingError):
+                            raise FileMappingError(target.args[0], path)
+                        else:
+                            return os.path.join(target, m.group(1)) if target else None
 
             return None
 
@@ -628,9 +639,10 @@ class FlatpakBuilder:
             ("ROOT/usr", None),
 
             # We map ROOT/usr => files and ROOT/etc => files/etc. This creates
-            # A conflict between ROOT/usr/etc and /ROOT/etc. Just assume there
-            # is nothing useful in /ROOT/usr/etc.
-            ("ROOT/usr/etc/", None),
+            # A conflict between ROOT/usr/etc and /ROOT/etc. Error out if we
+            # find files /usr/etc/
+            ("ROOT/usr/etc", None),
+            ("ROOT/usr/etc/", FileMappingError("/usr/etc should be empty")),
 
             ("ROOT/usr/", "files"),
             ("ROOT/etc/", "files/etc")
diff --git a/tests/test_flatpak_builder.py b/tests/test_flatpak_builder.py
index 47bd3c3..627991c 100644
--- a/tests/test_flatpak_builder.py
+++ b/tests/test_flatpak_builder.py
@@ -10,7 +10,7 @@ import pytest
 import yaml
 
 from flatpak_module_tools.flatpak_builder import (
-    FlatpakBuilder, FlatpakSourceInfo, FLATPAK_METADATA_BOTH, ModuleInfo
+    FileMappingError, FlatpakBuilder, FlatpakSourceInfo, FLATPAK_METADATA_BOTH, ModuleInfo
 )
 
 import gi
@@ -495,3 +495,36 @@ def test_export_long_filenames(testapp_source, tmpdir, arch):
     binfiles = sorted(os.listdir(tmpdir / "processed/files/bin"))
     assert binfiles == ["testapp", verylongname, veryverylongname,
                         "zzzlink", "zzzlink2", "zzzlink3"]
+
+
+@pytest.mark.parametrize("add_file", (True, False))
+def test_usr_etc(runtime_source, tmpdir, arch, add_file):
+    """
+    Test that we error out cleanly if a file is found in /usr/etc
+    """
+
+    os.makedirs(tmpdir / "root/usr/etc")
+    if add_file:
+        with open(tmpdir / "root/usr/etc/hello.txt", "w") as f:
+            os.fchmod(f.fileno(), 0o0755)
+
+    check_call(["tar", "cfv", "export.tar", "-H", "pax", "--sort=name",
+                "root"], cwd=tmpdir)
+
+    workdir = str(tmpdir / "work")
+    os.mkdir(workdir)
+
+    builder = FlatpakBuilder(runtime_source, workdir, "root",
+                             oci_arch=arch.oci)
+
+    def export():
+        with open(tmpdir / "export.tar", "rb") as f:
+            outfile, manifest_file = (builder._export_from_stream(f, close_stream=False))
+
+    if add_file:
+        with pytest.raises(FileMappingError,
+                           match=r"root/usr/etc/hello.txt: /usr/etc should be empty"):
+            export()
+    else:
+        # An empty /usr/etc is fine
+        export()