Add error handling when data file length does not match spec

DataParser.Console/Core.fs

@@ -7,7 +7,8 @@ type Error =
     | DataFileNameFormatError of fileName: string
     | UnexpectedFormatHeader of string
     | UnexpectedFormatLine of string
-    | UnparsableValue of obj
+    | UnparsableValue of string
+    | DataFileLineLengthShorterThanSpec of string
     | UnparsableFormatFile of fileContent: string
 
 let (<*>) f x =

DataParser.Console/DataFiles.fs

@@ -45,19 +45,43 @@ let getDataFileFormat (fileFormatLookup: Map<FormatName, FormatLine list>) (file
 let parseDataFileLine (formatLines : FormatLine list) (dataFileLine : string) : Result<JsonObject, Error list> =
     let parseDataType dataType (s: byte array) : Result<obj, Error list> =
         match dataType with
-        | JBool -> if s = [|TrueByte|] then Ok true elif s = [|FalseByte|] then Ok false else Error [UnparsableValue s] 
-        | JInt -> match System.Int32.TryParse (s, CultureInfo.InvariantCulture) with true, i -> Ok i | false, _ -> Error [UnparsableValue s]
-        | JString -> Ok <| let result = Encoding.UTF8.GetString s in result.Trim()
+        | JBool ->
+            if s = [|TrueByte|]
+            then Ok true
+            elif s = [|FalseByte|]
+            then Ok false
+            else
+                let errorValue = Encoding.UTF8.GetString s
+                Error [UnparsableValue errorValue] 
+        | JInt ->
+            match System.Int32.TryParse (s, CultureInfo.InvariantCulture) with
+            | true, i -> Ok i
+            | false, _ ->
+                let errorValue = Encoding.UTF8.GetString s
+                Error [UnparsableValue errorValue] 
+        | JString ->
+            let result = Encoding.UTF8.GetString s
+            Ok <| result.Trim()
 
-    let folder (stream : MemoryStream, map) (FormatLine (columnName, width, dataType)) =
-        let byteArray = Array.create width 0uy
-        stream.ReadExactly(byteArray, 0, width)
-        let result = parseDataType dataType byteArray
-        stream, Map.add columnName result map
+    let folder result (FormatLine (columnName, width, dataType)) =
+        match result with
+        | Error e -> Error e
+        | Ok (stream : MemoryStream, map) ->
+            let byteArray = Array.create width 0uy
+            try
+                stream.ReadExactly(byteArray, 0, width)
+                let result = parseDataType dataType byteArray
+                Ok (stream, Map.add columnName result map)
+            with
+            | :? EndOfStreamException ->
+                let line = Encoding.UTF8.GetString (stream.ToArray())
+                Error [DataFileLineLengthShorterThanSpec line]
 
     let bytes : byte array = Encoding.UTF8.GetBytes dataFileLine
     use s = new MemoryStream(bytes)
-    let _, map = List.fold folder (s, Map.empty) formatLines
+    let initialState = Ok (s, Map.empty)
+    let map =
+        List.fold folder initialState formatLines
+        |> Result.bind (mapSequenceResult << snd)
 
     map
-    |> mapSequenceResult

DataParser.Tests/Tests.fs

@@ -130,6 +130,18 @@ let ``Given a format and a dataFileLine of Diabetes, parseDataFileLine returns a
 
     parseDataFileLine formatLines dataFileLine =! expected
 
+[<Xunit.Fact>]
+let ``Given a format and a dataFileLine shorter than format width, parseDataFileLine returns an Error`` () =
+    let dataFileLine = "Diabetes 1 1\n"
+    let formatLines = [
+        FormatLine ("name", 10, JsonDataType.JString)
+        FormatLine ("valid", 1, JsonDataType.JBool)
+        FormatLine("count", 3, JsonDataType.JInt)
+    ]
+    let expected : Result<JsonObject, Error list> = Error [DataFileLineLengthShorterThanSpec dataFileLine]
+
+    parseDataFileLine formatLines dataFileLine =! expected
+
 [<Xunit.Fact>]
 let ``Given a format and a dataFileLine of Asthma, parseDataFileLine returns an expected map`` () =
     let dataFileLine = "Asthma    0-14\n"