Increase robustness

coconut/command/command.py

@@ -1000,7 +1000,13 @@ def run_type_checking(self, paths=(), code=None):
             if code is not None:
                 logger.warn("--pyright only works on files, not code snippets or at the interpreter")
             if paths:
-                from pyright import main
+                try:
+                    from pyright import main
+                except ImportError:
+                    raise CoconutException(
+                        "coconut --pyright requires Pyright",
+                        extra="run '{python} -m pip install coconut[pyright]' to fix".format(python=sys.executable),
+                    )
                 args = ["--project", config_file, "--pythonversion", self.type_checking_version] + list(paths)
                 main(args)
 

coconut/command/mypy.py

@@ -34,7 +34,7 @@
     from mypy.api import run
 except ImportError:
     raise CoconutException(
-        "--mypy flag requires MyPy library",
+        "coconut --mypy requires MyPy",
         extra="run '{python} -m pip install coconut[mypy]' to fix".format(python=sys.executable),
     )
 

coconut/command/util.py

@@ -510,7 +510,10 @@ def update_pyright_config(python_version=None):
     update_existing = os.path.exists(pyright_config_file)
     with univ_open(pyright_config_file, "r+" if update_existing else "w") as config_file:
         if update_existing:
-            config = readfile(config_file, in_json=True)
+            try:
+                config = readfile(config_file, in_json=True)
+            except ValueError:
+                raise CoconutException("invalid JSON syntax in " + repr(pyright_config_file))
         else:
             config = extra_pyright_args.copy()
         config["extraPaths"] = [install_stubs()]