slither-flat: Add support for --contract

slither/tools/flattening/flattening.py

@@ -125,15 +125,7 @@ class Flattening:
         exported.add(contract.name)
         list_contract.append(self._source_codes[contract])
 
-
-    def export(self, target=None):
-
-        if not self.DEFAULT_EXPORT_PATH.exists():
-            self.DEFAULT_EXPORT_PATH.mkdir(parents=True)
-
-        if target is None:
-            for contract in self._slither.contracts_derived:
-                ret = []
+    def _export(self, contract, ret):
         self._export_contract(contract, set(), ret)
         path = Path(self.DEFAULT_EXPORT_PATH, f'{contract.name}.sol')
         logger.info(f'Export {path}')
@@ -144,3 +136,20 @@ class Flattening:
                 f.write('pragma experimental ABIEncoderV2;\n')
             f.write('\n'.join(ret))
             f.write('\n')
+
+    def export(self, target=None):
+
+        if not self.DEFAULT_EXPORT_PATH.exists():
+            self.DEFAULT_EXPORT_PATH.mkdir(parents=True)
+
+        ret = []
+        if target is None:
+            for contract in self._slither.contracts_derived:
+                self._export(contract, ret)
+        else:
+            contract = self._slither.get_contract_from_name(target)
+            if contract is None:
+                logger.error(f'{target} not found')
+            else:
+                self._export(contract, ret)
+