From 9c65515e7a7d466be2168c65ea5a88a40cd3f248 Mon Sep 17 00:00:00 2001
From: VanL <van.lindberg@gmail.com>
Date: Fri, 6 Jan 2012 00:12:06 +0000
Subject: [PATCH] Add detect function in _xls. Update yaml, csv, and tsv
 detection functions to catch other errors when faced with invalid input.

---
 tablib/formats/_csv.py  |  4 ++--
 tablib/formats/_tsv.py  |  2 +-
 tablib/formats/_xls.py  | 20 ++++++++++++++++++++
 tablib/formats/_yaml.py |  4 ++--
 4 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/tablib/formats/_csv.py b/tablib/formats/_csv.py
index 3a4c374..549259c 100644
--- a/tablib/formats/_csv.py
+++ b/tablib/formats/_csv.py
@@ -51,5 +51,5 @@ def detect(stream):
     try:
         csv.Sniffer().sniff(stream)
         return True
-    except csv.Error:
-        return False
\ No newline at end of file
+    except (csv.Error, TypeError):
+        return False
diff --git a/tablib/formats/_tsv.py b/tablib/formats/_tsv.py
index f581f81..ac9554c 100644
--- a/tablib/formats/_tsv.py
+++ b/tablib/formats/_tsv.py
@@ -55,5 +55,5 @@ def detect(stream):
     try:
         csv.Sniffer().sniff(stream, delimiters='\t')
         return True
-    except csv.Error:
+    except (csv.Error, TypeError):
         return False
diff --git a/tablib/formats/_xls.py b/tablib/formats/_xls.py
index 89d2845..6530d91 100644
--- a/tablib/formats/_xls.py
+++ b/tablib/formats/_xls.py
@@ -6,6 +6,8 @@
 import sys
 
 from tablib.compat import BytesIO, xlwt
+from tablib.packages import xlrd
+from tablib.packages.xlrd.biffh import XLRDError
 import tablib
 
 title = 'xls'
@@ -16,6 +18,24 @@ wrap = xlwt.easyxf("alignment: wrap on")
 bold = xlwt.easyxf("font: bold on")
 
 
+def detect(stream):
+    """Returns True if given stream is a readable excel file."""
+    try:
+        xlrd.open_workbook(file_contents=stream)
+        return True
+    except (TypeError, XLRDError):
+        pass 
+    try:
+        xlrd.open_workbook(file_contents=stream.read())
+        return True
+    except (AttributeError, XLRDError):
+        pass
+    try:
+        xlrd.open_workbook(filename=stream)
+        return True
+    except:
+        return False
+
 
 def export_set(dataset):
     """Returns XLS representation of Dataset."""
diff --git a/tablib/formats/_yaml.py b/tablib/formats/_yaml.py
index 0eab78e..c9ffbd3 100644
--- a/tablib/formats/_yaml.py
+++ b/tablib/formats/_yaml.py
@@ -60,5 +60,5 @@ def detect(stream):
             return True
         else:
             return False
-    except yaml.parser.ParserError:
-        return False
\ No newline at end of file
+    except (yaml.parser.ParserError, yaml.reader.ReaderError):
+        return False