Handle the case where the is no resolver

Some python packages, e.g. pytz, are purely written in python and do not
have any other dependencies. In those cases, a `resolver` is not set on
the compiler, causing `AttributeError` exceptions in various places.

This commit performs a `None` check on the `resolver` attribute before
proceeding to access nested attributes.

Fixes: #304

Signed-off-by: Luiz Carvalho <[email protected]>

Author: lcarva

src/pybuild_deps/scripts/compile.py

@@ -112,7 +112,9 @@ def compile(
     compiler = BuildDependencyCompiler(repository)
     try:
         results = compiler.resolve(dependencies)
-        hashes = compiler.resolver.resolve_hashes(results) if generate_hashes else None
+        hashes = None
+        if compiler.resolver is not None and generate_hashes:
+            hashes = compiler.resolver.resolve_hashes(results)
     except (PipToolsError, PyBuildDepsError) as e:
         log.error(str(e))
         sys.exit(2)
@@ -142,10 +144,15 @@ def compile(
         emit_find_links=True,
         emit_options=True,
     )
+    unsafe_packages = None
+    unsafe_requirements = None
+    if compiler.resolver is not None:
+        unsafe_packages = compiler.resolver.unsafe_packages
+        unsafe_requirements = compiler.resolver.unsafe_constraints
     writer.write(
         results=results,
-        unsafe_packages=compiler.resolver.unsafe_packages,
-        unsafe_requirements=compiler.resolver.unsafe_constraints,
+        unsafe_packages=unsafe_packages,
+        unsafe_requirements=unsafe_requirements,
         markers={
             key_from_ireq(ireq): ireq.markers for ireq in dependencies if ireq.markers
         },

tests/test_main.py

@@ -255,3 +255,13 @@ def test_compile_consistent_ordering(runner: CliRunner, tmp_path: Path):
     )
     assert result2.exit_code == 0
     assert outfile1.read_text() == outfile2.read_text()
+
+
+def test_compile_package_without_dependencies(runner: CliRunner, tmp_path: Path):
+    """Test compile function with a package that has no dependencies."""
+    chdir(tmp_path)
+    requirements_path: Path = tmp_path / "requirements.txt"
+    requirements_path.write_text("pytz==2024.1")
+    outfile = tmp_path / "outfile"
+    result = runner.invoke(main.cli, args=["compile", "-o", str(outfile)])
+    assert result.exit_code == 0