From cff4d491ea15e1ea9541813df99cf961b4d4a682 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Wed, 23 Jun 2021 09:07:39 +0530
Subject: [PATCH] Close a bunch of file objects explicitly

---
 src/calibre/ebooks/oeb/polish/container.py |  6 ++++--
 src/calibre/spell/dictionary.py            |  6 ++++--
 src/calibre/utils/imghdr.py                | 12 +++++++++++-
 3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/src/calibre/ebooks/oeb/polish/container.py b/src/calibre/ebooks/oeb/polish/container.py
index 9ec4b7704f..753e83d018 100644
--- a/src/calibre/ebooks/oeb/polish/container.py
+++ b/src/calibre/ebooks/oeb/polish/container.py
@@ -611,7 +611,8 @@ class Container(ContainerBase):  # {{{
         :param decode: If True and the file has a text based MIME type, decode it and return a unicode object instead of raw bytes.
         :param normalize_to_nfc: If True the returned unicode object is normalized to the NFC normal form as is required for the EPUB and AZW3 file formats.
         '''
-        ans = self.open(name).read()
+        with self.open(name) as nf:
+            ans = nf.read()
         mime = self.mime_map.get(name, guess_type(name))
         if decode and (mime in OEB_STYLES or mime in OEB_DOCS or mime == 'text/plain' or mime[-4:] in {'+xml', '/xml'}):
             ans = self.decode(ans, normalize_to_nfc=normalize_to_nfc)
@@ -1205,7 +1206,8 @@ class EpubContainer(Container):
         container_path = join(self.root, 'META-INF', 'container.xml')
         if not exists(container_path):
             raise InvalidEpub('No META-INF/container.xml in epub')
-        container = safe_xml_fromstring(open(container_path, 'rb').read())
+        with open(container_path, 'rb') as cf:
+            container = safe_xml_fromstring(cf.read())
         opf_files = container.xpath((
             r'child::ocf:rootfiles/ocf:rootfile'
             '[@media-type="%s" and @full-path]'%guess_type('a.opf')
diff --git a/src/calibre/spell/dictionary.py b/src/calibre/spell/dictionary.py
index 3e0d236c4d..4f450c2715 100644
--- a/src/calibre/spell/dictionary.py
+++ b/src/calibre/spell/dictionary.py
@@ -52,7 +52,8 @@ def builtin_dictionaries():
     if _builtins is None:
         dics = []
         for lc in glob.glob(os.path.join(P('dictionaries', allow_user_override=False), '*/locales')):
-            locales = list(filter(None, open(lc, 'rb').read().decode('utf-8').splitlines()))
+            with open(lc, 'rb') as lcf:
+                locales = list(filter(None, lcf.read().decode('utf-8').splitlines()))
             locale = locales[0]
             base = os.path.dirname(lc)
             dics.append(Dictionary(
@@ -67,7 +68,8 @@ def custom_dictionaries(reread=False):
     if _custom is None or reread:
         dics = []
         for lc in glob.glob(os.path.join(config_dir, 'dictionaries', '*/locales')):
-            locales = list(filter(None, open(lc, 'rb').read().decode('utf-8').splitlines()))
+            with open(lc, 'rb') as cdf:
+                locales = list(filter(None, cdf.read().decode('utf-8').splitlines()))
             try:
                 name, locale, locales = locales[0], locales[1], locales[1:]
             except IndexError:
diff --git a/src/calibre/utils/imghdr.py b/src/calibre/utils/imghdr.py
index f7bc9b0dc1..2b806a60a9 100644
--- a/src/calibre/utils/imghdr.py
+++ b/src/calibre/utils/imghdr.py
@@ -40,14 +40,24 @@ def identify(src):
     ''' Recognize file format and sizes. Returns format, width, height. width
     and height will be -1 if not found and fmt will be None if the image is not
     recognized. '''
-    width = height = -1
+    needs_close = False
 
     if isinstance(src, unicode_type):
         stream = lopen(src, 'rb')
+        needs_close = True
     elif isinstance(src, bytes):
         stream = ReadOnlyFileBuffer(src)
     else:
         stream = src
+    try:
+        return _identify(stream)
+    finally:
+        if needs_close:
+            stream.close()
+
+
+def _identify(stream):
+    width = height = -1
 
     pos = stream.tell()
     head = stream.read(HSIZE)