Search Changes in IMAPClient 1.0

Posted on September 15, 2015

Following on from last week's post about the upcoming IMAPClient 1.0 release, I'd like to draw attention to some significant, compatibility breaking changes related to the handling of search criteria.

IMAPClient's methods that accept search criteria (search, sort, thread, gmail_search) have been changed to provide take criteria in a more straightforward and robust way. In addition, the way the charset argument interacts with search criteria has been improved. These changes make it easier to pass search criteria and have them handled correctly but unfortunately also mean that small changes may be required to existing code that uses IMAPClient.

Search criteria

The preferred way to specify criteria now is as a list of strings, ints and dates (where relevant). The list should be flat with all the criteria parts run together. Where a criteria takes an argument, just provide it as the next element in the list.

Some valid examples:

c.search(['DELETED'])
c.search(['NOT', 'DELETED'])
c.search(['FLAGGED', 'SUBJECT', 'foo', 'BODY', 'hello world'])
c.search(['NOT', 'DELETED', 'SMALLER', 1000])
c.search(['SINCE', date(2006, 5, 3)])

IMAPClient will perform all required conversion, quoting and encoding. Callers do not need to and should not attempt to do this themselves. IMAPClient will automatically send criteria parts as IMAP literals when required (i.e. when the encoded part is 8-bit).

Some previously accepted ways of passing search criteria will not work as they did in previous versions of IMAPClient. Small changes will be required in these cases. Here are some examples of how to update code written against older versions of IMAPClient:

c.search(['NOT DELETED'])    # Before
c.search(['NOT', 'DELETED']) # After

c.search(['TEXT "foo"'])     # Before
c.search(['TEXT', 'foo'])    # After (IMAPClient will add the quotes)

c.search(['DELETED', 'TEXT "foo"'])    # Before
c.search(['DELETED', 'TEXT', 'foo'])   # After

c.search(['SMALLER 1000'])    # Before
c.search(['SMALLER', 1000])   # After

It is also possible to pass a single string as the search criteria. IMAPClient will not attempt quoting in this case, allowing the caller to specify search criteria at a lower level. Specifying criteria using a sequence of strings is preferable however. The following examples (equivalent to those further above) are valid:

c.search('DELETED')
c.search('NOT DELETED')
c.search('FLAGGED SUBJECT "foo" BODY "hello world"')
c.search('NOT DELETED SMALLER 1000')
c.search('SINCE 03-May-2006')

Search charset

The way that the search charset argument is handled has also changed.

Any unicode criteria arguments will now be encoded by IMAPClient using the supplied charset. The charset must refer to an encoding that is capable of handling the criteria's characters or an error will occur. The charset must obviously also be one that the server supports! (UTF-8 is common)

Any criteria given as bytes will not be changed by IMAPClient, but the provided charset will still be passed to the IMAP server. This allows already encoding criteria to be passed through as-is. The encoding referred to by charset should match the actual encoding used for the criteria.

The following are valid examples:

c.search(['TEXT', u'\u263a'], 'utf-8')         # IMAPClient will apply UTF-8 encoding
c.search([b'TEXT', b'\xe2\x98\xba'], 'utf-8')  # Caller has already applied UTF-8 encoding

The documentation and tests for search, gmail_search, sort and thread has updated to account for these changes and have also been generally improved.

For those willing to try out the changes now please install from IMAPClient's tip. Any feedback on the changes and/or documentation would be hugely appreciated.