Report parse errors instead of throwing an exception

Fixes protofire#245

lib/index.js

@@ -13,21 +13,34 @@ function parseInput(inputStr) {
     // first we try to parse the string as we normally do
     return parser.parse(inputStr, { loc: true, range: true })
   } catch (e) {
-    try {
-      // using 'loc' may throw when inputStr is empty or only has comments
-      return parser.parse(inputStr, {})
-    } catch (error) {
-      // if the parser fails in both scenarios (with and without 'loc')
-      // we throw the error, as we may be facing an invalid Solidity file
-      throw new Error(error)
-    }
+    // using 'loc' may throw when inputStr is empty or only has comments
+    return parser.parse(inputStr, {})
   }
 }
 
 function processStr(inputStr, config = {}, fileName = '') {
   config = applyExtends(config)
 
-  const ast = parseInput(inputStr)
+  let ast
+  try {
+    ast = parseInput(inputStr)
+  } catch (e) {
+    if (e instanceof parser.ParserError) {
+      const reporter = new Reporter([], config)
+      for (const error of e.errors) {
+        reporter.addReport(
+          error.line,
+          error.column,
+          Reporter.SEVERITY.ERROR,
+          `Parse error: ${error.message}`
+        )
+      }
+      return reporter
+    } else {
+      throw e
+    }
+  }
+
   const tokens = parser.tokenize(inputStr, { loc: true })
   const reporter = new Reporter(tokens, config)
   const listener = new TreeListener(checkers(reporter, config, inputStr, tokens, fileName))

test/parse-error.js

@@ -0,0 +1,15 @@
+const assert = require('assert')
+const { assertErrorCount } = require('./common/asserts')
+const linter = require('./../lib/index')
+
+describe('Parse error', () => {
+  it('should report parse errors', () => {
+    const report = linter.processStr('contract Foo {', {})
+
+    assertErrorCount(report, 1)
+    const error = report.reports[0]
+    assert.equal(error.line, 1)
+    assert.equal(error.column, 14)
+    assert.ok(error.message.startsWith("Parse error: mismatched input '<EOF>'"))
+  })
+})