RustClippyLintBear: Linter support for Rust code.

Closes #50

bears/rust/RustClippyLintBear.py

@@ -0,0 +1,63 @@
+import json
+from os import linesep
+from shutil import which
+
+from coalib.bears.GlobalBear import GlobalBear
+from coalib.misc.Shell import run_shell_command
+from coalib.results.Result import Result
+from coalib.results.RESULT_SEVERITY import RESULT_SEVERITY
+
+
+class RustClippyLintBear(GlobalBear):
+    LANGUAGES = {'Rust'}
+    AUTHORS = {'The coala developers'}
+    AUTHORS_EMAILS = {'coala-devel@googlegroups.com'}
+    LICENSE = 'AGPL-3.0'
+    CAN_DETECT = {
+            'Formatting',
+            'Unused Code',
+            'Syntax',
+            'Unreachable Code',
+            'Smell',
+            'Code Simplification'
+    }
+    EXECUTABLE = 'cargo'
+    SEVERITY_MAP = {
+            # TODO: are there more?
+            'warning': RESULT_SEVERITY.NORMAL,
+            'error': RESULT_SEVERITY.MAJOR,
+    }
+
+    @classmethod
+    def check_prerequisites(cls):
+        # TODO: - check for clippy itself
+        #       - clippy also works via rustup nightly, so also check that.
+        if which('cargo') is None:
+            return 'cargo is not installed.'
+        else:
+            return True
+
+    def run(self):
+        args = ('clippy', '--quiet', '--color', 'never',
+                '--', '-Z', 'unstable-options', '--error-format', 'json',
+                '--test')
+        _, stderr_output = run_shell_command(
+            (self.EXECUTABLE,) + args,
+            cwd=self.get_config_dir(),
+            universal_newlines=True)
+        for line in stderr_output.split(linesep):
+            if not line:
+                continue
+            yield self.new_result(json.loads(line))
+
+    def new_result(self, issue):
+        span = issue['spans'][0]
+        return Result.from_values(
+                origin=self.__class__.__name__,
+                message=issue['message'],
+                file=span['file_name'],
+                line=span['line_start'],
+                end_line=span['line_end'],
+                column=span['column_start'],
+                end_column=span['column_end'],
+                severity=self.SEVERITY_MAP[issue['level']])