Fail gracefully if solc doesn't find any contracts. Information how t…

.gitignore

@@ -49,3 +49,6 @@ docs/_build
 
 # Known Contracts
 **/known_contracts.json
+
+# py.test cache
+.cache

README.md

@@ -5,13 +5,15 @@
 [![PyPi downloads](https://pypip.in/d/py-solc/badge.png)](https://pypi.python.org/pypi/py-solc)
 
 
-Python wrapper around the `solc` solidity compiler.
+Python wrapper around the `solc` Solidity compiler.
 
 
 # Dependency
 
 This library requires the `solc` executable to be present.
 
+solc 0.3.5 or newer is required. [solc installation instructions](http://solidity.readthedocs.io/en/latest/installing-solidity.html)
+
 
 # Quickstart
 

solc/exceptions.py

@@ -4,3 +4,7 @@ class SolcError(Exception):
 
 class CompileError(Exception):
     pass
+
+
+class ContractsNotFound(Exception):
+    """No contracts was found in the target folder."""

solc/main.py

@@ -6,6 +6,7 @@
 
 from .exceptions import (
     SolcError,
+    ContractsNotFound,
 )
 
 from .utils.formatting import (
@@ -39,7 +40,15 @@ def get_solc_version():
 
 
 def _parse_compiler_output(stdoutdata):
-    contracts = json.loads(stdoutdata)['contracts']
+
+    output = json.loads(stdoutdata)
+
+    if "contracts" not in output:
+        # {'sources': {}, 'version': 'xxx'}
+        # solc did not pick up any contracts
+        raise ContractsNotFound(output)
+
+    contracts = output['contracts']
 
     for _, data in contracts.items():
         data['abi'] = json.loads(data['abi'])

tests/compilation/test_compile_empty.py

@@ -0,0 +1,21 @@
+import os
+import tempfile
+
+import pytest
+
+from solc import (
+    compile_files,
+)
+
+from solc.exceptions import ContractsNotFound
+
+
+def test_compile_empty_folder():
+    """Execute compile on a folder without contracts."""
+
+    tmpdirname = tempfile.mkdtemp()
+    try:
+        with pytest.raises(ContractsNotFound):
+            compile_files(tmpdirname)
+    finally:
+        os.rmdir(tmpdirname)