Shad Storhaug created LUCENENET-620:
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Summary: Automate Generation of QueryParser to C#
Key: LUCENENET-620
URL: https://issues.apache.org/jira/browse/LUCENENET-620
Project: Lucene.Net
Issue Type: Wish
Components: Lucene.Net.QueryParser
Reporter: Shad Storhaug
The Lucene team is using a tool called
[javacc|https://github.com/javacc/javacc] to generate the main business logic
behind the query parsers. If we had a similar tool it could help:
* Speed up the process of porting/upgrading QueryParser
* Reduce the number of bugs in these modules caused by doing it manually
* Most importantly, QueryParser could potentially be generated without using
exceptions for control flow
The javacc tool uses a configuration file as input and creates java code as
output. Here are some examples of those configuration files:
*
https://github.com/apache/lucene-solr/blob/releases/lucene-solr/4.8.1/lucene/queryparser/src/java/org/apache/lucene/queryparser/classic/QueryParser.jj
*
https://github.com/apache/lucene-solr/blob/releases/lucene-solr/4.8.1/lucene/queryparser/src/java/org/apache/lucene/queryparser/surround/parser/QueryParser.jj
This has not been fully researched, but there are at least 2 potential ways we
could approach this:
# Find a similar tool to javacc in .NET that supports similar options that were
used in javacc, and create a converter tool to change the javacc configuration
into a configuration that the .NET tool supports.
# Do a direct port of javacc to C#, and fix its logic to use a more efficient
control flow mechanism than exceptions (perhaps {{goto}} would be the most
direct replacement).
It seems [according to this
document|https://dzone.com/articles/antlr-and-javacc-parser-generators] that
using a port of javacc should be our first choice because of the performance
benchmarks of the resultant code. And certainly that would eliminate the risk
of having a .NET tool not support an option that we need either now or for some
future version of Lucene.
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