On Sat, Aug 4, 2012 at 3:50 AM, Christopher Genovese
<genovese@cmu.edu> wrote:
I am writing an application layer on top of org that uses the
entry mapping API, but I needed both negation of complex
selections and heading searches. Because the current tag query
parser does not handle parenthesized expressions, it does not
allow negating complex queries. At first, I wrote a workaround
solution that mimics/specializes the mapping API, but that
approach seemed inelegant and harder to maintain.
So instead I implemented a full parser for tag queries with a
number of useful features (see the labeled Notes at the bottom
for further comments on these features):
1. Parenthesized expressions to arbitrary depth are allowed.
2. A '-' can be used to negate a parenthesized term. [Note a]
3. Regex's in {} can contain braces escaped by doubling: {{ }}. [Note b]
4. Supports fast property search on HEADING and PRIORITY. [Note c]
5. Handles hyphens in property names properly. [Note d,h]
6. Allows only the proper comparison operators, including ==. [Note e,h]
7. Allows spaces around operators and terms for readability. [Note f]
8. Matchers use the original expression order; not a big
deal, but free.
9. The error messages during parsing are reasonably helpful.
10. Several bug fixes and a cleaner `org-make-tags-matcher'. [Note h]
I'm submitting the code for your consideration, with the
goal of eventually incorporating this into org.el. I would be
happy to hear any comments or suggestions you have. As I'll describe
below, this involves relatively minor changes to two existing
functions and adding a few new support functions. I've attached two
files org-tag-query-parse.el (the code) and tag-query-tests.el (a
collection of tests built on a simple framework). I've also
put the files in http://www.stat.cmu.edu/~genovese/emacs/. The
comments in both files will I hope be helpful.
At the risk of going on too long, I'd like to add a few comments
about the code and tests. First, the two existing functions that
are affected in the code are `org-make-tags-matcher' and
`org-scan-tags'. In the new version of the former, I've extracted
out both kinds of query parsing, leading to a shorter and cleaner
function. The new version of the latter differs in only a couple
*very minor* places that capture two values that were already
being computed anyway (see the diff reproduced in the comments).
Btw, I'm working from the 7.8.11 code.
Loading org-tag-query-parse.el does not change the original
functions. Instead, I've added a `-NEW' to the names of these
functions and saved the originals also with a `-ORIGINAL' added.
After loading the file, you can choose a version to try by doing
(org-tmp-use-tag-parser 'new)
and
(org-tmp-use-tag-parser 'original)
or do (org-tmp-use-tag-parser) to toggle between versions.
You can also just use the names with suffixes directly.
I'd also suggest byte-compiling the file.
I think the place to start looking at the code is the new version
of `org-make-tags-matcher'. The main entry function for the new
parser is `org-tag-query-parse', though the real workhorse is
actually the function `org-tag-query-parse-1'. There is also a
new function `org-todo-query-parse' which just extracts the
existing todo matching method. (I didn't do anything with that
method as the manual makes it clear that it is of secondary
importance.) I think the modularity here makes
`org-make-tags-matcher' and each separate parser easier to read
and understand.
The other substantial piece (in terms of lines of code) is a utility
macro `org-match-cond' that is used throughout and makes the main
parser much more readable IMHO. Admittedly, I went a bit
overboard in optimizing it; the first version worked fine
but this one produces really nice code. I'd suggest ignoring this
code (in section "Parsing utility for readable matchers") on
first pass. The docstring is pretty complete, and its use is more
or less self-explanatory. Most of its work is done at compile time.
To run the tests, load org-tag-query-parse.el and tag-query-tests.el
and do
(tag-test-run :results) ; use :summary for a brief summary of all runs
(tag-test-other-tests) ; miscellaneous other tests, including scanning
or name individual suites. They are at the moment:
(tag-test-run :results 'org-comparison-1) ; or use :summary
(tag-test-run :results 'org-comparison-2)
(tag-test-run :results 'match-results-1)
(tag-test-run :results 'match-results-2)
(tag-test-run :results 'should-error-1)
If you have other ideas for tests or find any bugs, please let me
know. Sorry for the homegrown framework; it just sort of grew and
then I was too tired to rewrite the tests. One complication here
is that the original and new algorithms produce different term
orders and use a few different functions. The function
tag-test-transform transforms original results to the new
algorithms conventions, but it does not handle PRIORITY or
HEADING matches at the moment. Use the tree form of the tess (see
match-results-1 for example) on these. Btw, I've run the tests on
GNU Emacs 23.2 and 24.1 (running on OS X lion).
Notes:
a. There is no need to introduce a new character such as ! for
negation because the semantics of the - are clear and are
consistent with its use for tags. A - binds more tightly
than & which in turn binds more tightly than |. A +
selector can also be used for positive selection of a
parenthesized term but it is equivalent to using no
selector, just as for tags.
b. Because \'s are so heavily used in regex's and because they
have to be doubled in strings, using \'s for an additional
escape layer would be messy, ambiguous, and hard to read.
Only the {}'s need to be escaped and the doubling escapes
{{ -> { and }} -> } are simple, readable, and fast to
parse. For example: "+{abc\\{{3,7\\}}}" gives the regex
"abc\\{3,7\\}". Parity makes correctness clear at a glance.
c. Because headline (and priority) searches can be useful and
powerful, and because the information on those fields is
*already processed* in `org-scan-tags', we get those
special searches *essentially for free*, requiring only two
minor changes to `org-scan-tags'. See the unified diff in
comments. The special PRIORITY property already exists; I
added the special HEADING property for these purposes. I'm
open to changing the name of course, but I do think the
feature is both useful and elegant. (I'm using it in my
application, for instance.)
d. I did not see it in the manual, but I think that property names
with hyphens should have these \-escaped -'s in the query
string, with the escaping slashes removed in the produced
matcher. This is not currently done, but the new version does.
See Note h for details.
e. It seems desirable to support both = and == as equality operators
since the latter is so common by habit. The new version allows
this explicitly. The original version does as well, but the
regex for the comparison operator also allows other operators
<<, ><, >>, =>, and >= as well, which can produce bad matchers.
See Note h for details.
f. Currently, spaces are ignored around &, |, the implicit & between
terms, around the comparison operators in property searches,
and around +/- selectors. Spaces are not ignored inside {}'s
for a regexp match.
g. The current code also allows +/- selectors before property
comparisons. I don't really like this because
+PROP<>"something" and -PROP="something" have the same
meaning but look very different. But the new code does
support this. As a side note, there's really no need for
the & characters as +/- serve the and/and-not function
completely. But again, no prob.
h. A few bugs detected in the 7.8.11 code:
+ Faulty test for todo matcher in org-make-tags-matcher
(string-match "/+" match)
Ex: (org-make-tags-matcher "PROP={^\\s-*// .*$}") produces
an erroneous matcher:
("PROP={^\\s-*// .*$}" progn
(setq org-cached-props nil)
(member "PROP" tags-list))
For all practical purposes it will be enough to do:
(string-match "\\(/\\(!\\)?\\s-*\\)[^{}\"]*$" match)
instead of the current test in org-make-tags-matcher.
This works as long as the TODO keywords do not contain a
right brace or quotation marks. (In most other cases, the
new parser should give an error message at parse time.)
A technicality: this is /not/ a complete solution because
arbitrary strings can be TODO keywords. For instance,
both PROP={/!} and PROP="/!{/!}" are valid TODO keywords
(it works!) *and* valid property comparisons. So, a pattern
alone is insufficient. We want to find the first slash
that is not enclosed in {}'s or ""'s; if found, a todo
match is needed. The function `org-find-todo-query' does
this and (org-find-todo-query match) can be plugged in
directly replacing the above (string-match ...) in then
new `org-make-tags-matcher'.
But because the todo parsing uses {}'s for regex matches,
TODO keywords with {}'s are ignored anyway. So there's
no need to go beyond the fixed string-match above.
The function `org-todo-query-parse', which handles todo
parsing in the new version, makes this explicit.
+ Property names with -'s are not handled properly (cf. Note d)
Specifically, the escapes are not removed. Example:
(org-make-tags-matcher "PROP\\-WITH\\-HYPHENS=2")
produces
("PROP\\-WITH\\-HYPHENS=2" and
(progn
(setq org-cached-props nil)
(=
(string-to-number
(or (org-cached-entry-get nil "PROP\\-WITH\\-HYPHENS")
""))
2))
t)
The original code /does/ instead remove -'s from tag
names, which shouldn't have them anyway. I suspect that
this was intended for property names rather than tag
names. The new version fixes up property names but does
not allow -'s in tags.
+ Incorrect comparison operators allowed (cf. Note e)
The regular expression used is "[<=>]\\{1,2\\}" is used to
detect the comparison operators. But this can produce bad
matchers that fail opaquely at match time rather than
giving an appropriate error message at parse time.
Ex: (org-make-tags-matcher "P<<2") produces
("P<<2" and
(progn
(setq org-cached-props nil)
(nil
(string-to-number (or (org-cached-entry-get nil "P") "")) 2))
t)
This is fixed in the new version and delivers an error
message at parse time.
+ missing org-re (line 7179 in org.el) with posix classes
Minor consistency issue. This line does not occur in the new
code.
Thanks and regards,
Christopher Genovese