Handle short file json parse errors

src/Microsoft.Extensions.Configuration.Json/JsonConfigurationProvider.cs

@@ -52,18 +52,21 @@ public override void Load(Stream stream)
 
  private static string RetrieveErrorContext(JsonReaderException e, IEnumerable<string> fileContent)
  {
- string errorLine;
+ string errorLine = null;
  if (e.LineNumber >= 2)
  {
  var errorContext = fileContent.Skip(e.LineNumber - 2).Take(2).ToList();
- errorLine = errorContext[0].Trim() + Environment.NewLine + errorContext[1].Trim();
+ // Handle situations when the line number reported is out of bounds
+ if (errorContext.Count() >= 2)
+ {
+ errorLine = errorContext[0].Trim() + Environment.NewLine + errorContext[1].Trim();
+ }
  }
- else
+ if (string.IsNullOrEmpty(errorLine))
  {
  var possibleLineContent = fileContent.Skip(e.LineNumber - 1).FirstOrDefault();
  errorLine = possibleLineContent ?? string.Empty;
  }
-
  return errorLine;
  }
 

test/Microsoft.Extensions.Configuration.Json.Test/JsonConfigurationTest.cs

@@ -92,6 +92,18 @@ public void ThrowExceptionWhenUnexpectedEndFoundBeforeFinishParsing()
  Assert.NotNull(exception.Message);
  }
 
+ [Fact]
+ public void ThrowExceptionWhenMissingCurlyBeforeFinishParsing()
+ {
+ var json = @"
+ {
+ 'Data': {
+ ";
+
+ var exception = Assert.Throws<FormatException>(() => LoadProvider(json));
+ Assert.Contains("Could not parse the JSON file.", exception.Message);
+ }
+
  [Fact]
  public void ThrowExceptionWhenPassingNullAsFilePath()
  {