lib: regexp matching in 'subject' and 'from'

the idea is that you can run

% notmuch search subject:/<your-favourite-regexp>/
% notmuch search from:/<your-favourite-regexp>/

or

% notmuch search subject:"your usual phrase search"
% notmuch search from:"usual phrase search"

This feature is only available with recent Xapian, specifically
support for field processors is needed.

It should work with bindings, since it extends the query parser.

This is easy to extend for other value slots, but currently the only
value slots are date, message_id, from, subject, and last_mod. Date is
already searchable;  message_id is left for a followup commit.

This was originally written by Austin Clements, and ported to Xapian
field processors (from Austin's custom query parser) by yours truly.

doc/man7/notmuch-search-terms.rst

@@ -34,10 +34,14 @@ indicate user-supplied values):
 
 -  from:<name-or-address>
 
+-  from:/<regex>/
+
 -  to:<name-or-address>
 
 -  subject:<word-or-quoted-phrase>
 
+-  subject:/<regex>/
+
 -  attachment:<word>
 
 -  mimetype:<word>
@@ -71,6 +75,15 @@ subject of an email. Searching for a phrase in the subject is supported
 by including quotation marks around the phrase, immediately following
 **subject:**.
 
+If notmuch is built with **Xapian Field Processors** (see below) the
+**from:** and **subject** prefix can be also used to restrict the
+results to those whose from/subject value matches a regular expression
+(see **regex(7)**) delimited with //.
+
+::
+
+   notmuch search 'from:/bob@.*[.]example[.]com/'
+
 The **attachment:** prefix can be used to search for specific filenames
 (or extensions) of attachments to email messages.
 
@@ -220,13 +233,18 @@ Boolean and Probabilistic Prefixes
 ----------------------------------
 
 Xapian (and hence notmuch) prefixes are either **boolean**, supporting
-exact matches like "tag:inbox"  or **probabilistic**, supporting a more flexible **term** based searching. The prefixes currently supported by notmuch are as follows.
-
+exact matches like "tag:inbox" or **probabilistic**, supporting a more
+flexible **term** based searching. Certain **special** prefixes are
+processed by notmuch in a way not stricly fitting either of Xapian's
+built in styles. The prefixes currently supported by notmuch are as
+follows.
 
 Boolean
    **tag:**, **id:**, **thread:**, **folder:**, **path:**, **property:**
 Probabilistic
-   **from:**, **to:**, **subject:**, **attachment:**, **mimetype:**
+  **to:**, **attachment:**, **mimetype:**
+Special
+   **from:**, **query:**, **subject:**
 
 Terms and phrases
 -----------------
@@ -396,6 +414,7 @@ Currently the following features require field processor support:
 
 - non-range date queries, e.g. "date:today"
 - named queries e.g. "query:my_special_query"
+- regular expression searches, e.g. "subject:/^\\[SPAM\\]/"
 
 SEE ALSO
 ========

lib/Makefile.local

@@ -52,6 +52,7 @@ libnotmuch_cxx_srcs =		\
 	$(dir)/query.cc		\
 	$(dir)/query-fp.cc      \
 	$(dir)/config.cc	\
+	$(dir)/regexp-fields.cc	\
 	$(dir)/thread.cc
 
 libnotmuch_modules := $(libnotmuch_c_srcs:.c=.o) $(libnotmuch_cxx_srcs:.cc=.o)

lib/database.cc

@@ -21,6 +21,7 @@
 #include "database-private.h"
 #include "parse-time-vrp.h"
 #include "query-fp.h"
+#include "regexp-fields.h"
 #include "string-util.h"
 
 #include <iostream>
@@ -277,7 +278,8 @@ prefix_t prefix_table[] = {
 						NOTMUCH_FIELD_PROCESSOR },
 #endif
     { "from",			"XFROM",	NOTMUCH_FIELD_EXTERNAL |
-						NOTMUCH_FIELD_PROBABILISTIC },
+						NOTMUCH_FIELD_PROBABILISTIC |
+						NOTMUCH_FIELD_PROCESSOR },
     { "to",			"XTO",		NOTMUCH_FIELD_EXTERNAL |
 						NOTMUCH_FIELD_PROBABILISTIC },
     { "attachment",		"XATTACHMENT",	NOTMUCH_FIELD_EXTERNAL |
@@ -285,7 +287,8 @@ prefix_t prefix_table[] = {
     { "mimetype",		"XMIMETYPE",	NOTMUCH_FIELD_EXTERNAL |
 						NOTMUCH_FIELD_PROBABILISTIC },
     { "subject",		"XSUBJECT",	NOTMUCH_FIELD_EXTERNAL |
-						NOTMUCH_FIELD_PROBABILISTIC },
+						NOTMUCH_FIELD_PROBABILISTIC |
+						NOTMUCH_FIELD_PROCESSOR},
 };
 
 static void
@@ -309,7 +312,7 @@ _setup_query_field (const prefix_t *prefix, notmuch_database_t *notmuch)
 	else if (STRNCMP_LITERAL(prefix->name, "query") == 0)
 	    fp = (new QueryFieldProcessor (*notmuch->query_parser, notmuch))->release ();
 	else
-	    INTERNAL_ERROR("unsupported field processor prefix: %s\n", prefix->name);
+	    fp = (new RegexpFieldProcessor (prefix->name, *notmuch->query_parser, notmuch))->release ();
 
 	/* we treat all field-processor fields as boolean in order to get the raw input */
 	notmuch->query_parser->add_boolean_prefix (prefix->name, fp);

lib/regexp-fields.cc

@@ -0,0 +1,149 @@
+/* regexp-fields.cc - field processor glue for regex supporting fields
+ *
+ * This file is part of notmuch.
+ *
+ * Copyright © 2015 Austin Clements
+ * Copyright © 2016 David Bremner
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see https://www.gnu.org/licenses/ .
+ *
+ * Author: Austin Clements <aclements@csail.mit.edu>
+ *                David Bremner <david@tethera.net>
+ */
+
+#include "regexp-fields.h"
+#include "notmuch-private.h"
+#include "database-private.h"
+
+#if HAVE_XAPIAN_FIELD_PROCESSOR
+static void
+compile_regex (regex_t &regexp, const char *str)
+{
+    int err = regcomp (&regexp, str, REG_EXTENDED | REG_NOSUB);
+
+    if (err != 0) {
+	size_t len = regerror (err, &regexp, NULL, 0);
+	char *buffer = new char[len];
+	std::string msg;
+	(void) regerror (err, &regexp, buffer, len);
+	msg.assign (buffer, len);
+	delete buffer;
+
+	throw Xapian::QueryParserError (msg);
+    }
+}
+
+RegexpPostingSource::RegexpPostingSource (Xapian::valueno slot, const std::string &regexp)
+    : slot_ (slot)
+{
+    compile_regex (regexp_, regexp.c_str ());
+}
+
+RegexpPostingSource::~RegexpPostingSource ()
+{
+    regfree (&regexp_);
+}
+
+void
+RegexpPostingSource::init (const Xapian::Database &db)
+{
+    db_ = db;
+    it_ = db_.valuestream_begin (slot_);
+    end_ = db.valuestream_end (slot_);
+    started_ = false;
+
+    /* make sure we start on a matching value */
+    while (!at_end() && regexec (&regexp_, (*it_).c_str (), 0, NULL, 0) != 0) {
+	++it_;
+    }
+}
+
+Xapian::doccount
+RegexpPostingSource::get_termfreq_min () const
+{
+    return 0;
+}
+
+Xapian::doccount
+RegexpPostingSource::get_termfreq_est () const
+{
+    return get_termfreq_max () / 2;
+}
+
+Xapian::doccount
+RegexpPostingSource::get_termfreq_max () const
+{
+    return db_.get_value_freq (slot_);
+}
+
+Xapian::docid
+RegexpPostingSource::get_docid () const
+{
+    return it_.get_docid ();
+}
+
+bool
+RegexpPostingSource::at_end () const
+{
+    return it_ == end_;
+}
+
+void
+RegexpPostingSource::next (unused (double min_wt))
+{
+    if (started_ && ! at_end ())
+	++it_;
+    started_ = true;
+
+    for (; ! at_end (); ++it_) {
+	std::string value = *it_;
+	if (regexec (&regexp_, value.c_str (), 0, NULL, 0) == 0)
+	    break;
+    }
+}
+
+static inline Xapian::valueno _find_slot (std::string prefix)
+{
+    if (prefix == "from")
+	return NOTMUCH_VALUE_FROM;
+    else if (prefix == "subject")
+	return NOTMUCH_VALUE_SUBJECT;
+    else
+	throw Xapian::QueryParserError ("unsupported regexp field '" + prefix + "'");
+}
+
+RegexpFieldProcessor::RegexpFieldProcessor (std::string prefix, Xapian::QueryParser &parser_, notmuch_database_t *notmuch_)
+	: slot (_find_slot (prefix)), term_prefix (_find_prefix (prefix.c_str ())),
+	  parser (parser_), notmuch (notmuch_)
+{
+};
+
+Xapian::Query
+RegexpFieldProcessor::operator() (const std::string & str)
+{
+    if (str.at (0) == '/') {
+	if (str.at (str.size () - 1) == '/'){
+	    RegexpPostingSource *postings = new RegexpPostingSource (slot, str.substr(1,str.size () - 2));
+	    return Xapian::Query (postings->release ());
+	} else {
+	    throw Xapian::QueryParserError ("unmatched regex delimiter in '" + str + "'");
+	}
+    } else {
+	/* TODO replace this with a nicer API level triggering of
+	 * phrase parsing, when possible */
+	std::string quoted='"' + str + '"';
+	return parser.parse_query (quoted, NOTMUCH_QUERY_PARSER_FLAGS, term_prefix);
+    }
+}
+#endif

lib/regexp-fields.h

@@ -0,0 +1,77 @@
+/* regex-fields.h - xapian glue for semi-bruteforce regexp search
+ *
+ * This file is part of notmuch.
+ *
+ * Copyright © 2015 Austin Clements
+ * Copyright © 2016 David Bremner
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see https://www.gnu.org/licenses/ .
+ *
+ * Author: Austin Clements <aclements@csail.mit.edu>
+ *                David Bremner <david@tethera.net>
+ */
+
+#ifndef NOTMUCH_REGEXP_FIELDS_H
+#define NOTMUCH_REGEXP_FIELDS_H
+#if HAVE_XAPIAN_FIELD_PROCESSOR
+#include <sys/types.h>
+#include <regex.h>
+#include "database-private.h"
+#include "notmuch-private.h"
+
+/* A posting source that returns documents where a value matches a
+ * regexp.
+ */
+class RegexpPostingSource : public Xapian::PostingSource
+{
+ protected:
+    const Xapian::valueno slot_;
+    regex_t regexp_;
+    Xapian::Database db_;
+    bool started_;
+    Xapian::ValueIterator it_, end_;
+
+/* No copying */
+    RegexpPostingSource (const RegexpPostingSource &);
+    RegexpPostingSource &operator= (const RegexpPostingSource &);
+
+ public:
+    RegexpPostingSource (Xapian::valueno slot, const std::string &regexp);
+    ~RegexpPostingSource ();
+    void init (const Xapian::Database &db);
+    Xapian::doccount get_termfreq_min () const;
+    Xapian::doccount get_termfreq_est () const;
+    Xapian::doccount get_termfreq_max () const;
+    Xapian::docid get_docid () const;
+    bool at_end () const;
+    void next (unused (double min_wt));
+};
+
+
+class RegexpFieldProcessor : public Xapian::FieldProcessor {
+ protected:
+    Xapian::valueno slot;
+    std::string term_prefix;
+    Xapian::QueryParser &parser;
+    notmuch_database_t *notmuch;
+
+ public:
+    RegexpFieldProcessor (std::string prefix, Xapian::QueryParser &parser_, notmuch_database_t *notmuch_);
+
+    ~RegexpFieldProcessor () { };
+
+    Xapian::Query operator()(const std::string & str);
+};
+#endif
+#endif /* NOTMUCH_REGEXP_FIELDS_H */

test/T650-regexp-query.sh

@@ -0,0 +1,82 @@
+#!/usr/bin/env bash
+test_description='regular expression searches'
+. ./test-lib.sh || exit 1
+
+add_email_corpus
+
+
+if [ $NOTMUCH_HAVE_XAPIAN_FIELD_PROCESSOR -eq 0 ]; then
+    test_done
+fi
+
+notmuch search --output=messages from:cworth > cworth.msg-ids
+
+test_begin_subtest "regexp from search, case sensitive"
+notmuch search --output=messages from:/carl/ > OUTPUT
+test_expect_equal_file /dev/null OUTPUT
+
+test_begin_subtest "empty regexp or query"
+notmuch search --output=messages from:/carl/ or from:/cworth/ > OUTPUT
+test_expect_equal_file cworth.msg-ids OUTPUT
+
+test_begin_subtest "non-empty regexp and query"
+notmuch search  from:/cworth@cworth.org/ and subject:patch | notmuch_search_sanitize > OUTPUT
+cat <<EOF > EXPECTED
+thread:XXX   2009-11-18 [1/2] Carl Worth| Alex Botero-Lowry; [notmuch] [PATCH] Error out if no query is supplied to search instead of going into an infinite loop (attachment inbox unread)
+thread:XXX   2009-11-18 [1/2] Carl Worth| Ingmar Vanhassel; [notmuch] [PATCH] Typsos (inbox unread)
+thread:XXX   2009-11-18 [1/2] Carl Worth| Jan Janak; [notmuch] [PATCH] Older versions of install do not support -C. (inbox unread)
+thread:XXX   2009-11-18 [1/2] Carl Worth| Keith Packard; [notmuch] [PATCH] Make notmuch-show 'X' (and 'x') commands remove inbox (and unread) tags (inbox unread)
+thread:XXX   2009-11-18 [2/5] Carl Worth| Mikhail Gusarov, Keith Packard; [notmuch] [PATCH 1/2] Close message file after parsing message headers (inbox unread)
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "regexp from search, duplicate term search"
+notmuch search --output=messages from:/cworth/ > OUTPUT
+test_expect_equal_file cworth.msg-ids OUTPUT
+
+test_begin_subtest "long enough regexp matches only desired senders"
+notmuch search --output=messages 'from:"/C.* Wo/"' > OUTPUT
+test_expect_equal_file cworth.msg-ids OUTPUT
+
+test_begin_subtest "shorter regexp matches one more sender"
+notmuch search --output=messages 'from:"/C.* W/"' > OUTPUT
+{ echo id:1258544095-16616-1-git-send-email-chris@chris-wilson.co.uk; cat cworth.msg-ids; } > EXPECTED
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "regexp subject search, non-ASCII"
+notmuch search --output=messages subject:/accentué/ > OUTPUT
+echo id:877h1wv7mg.fsf@inf-8657.int-evry.fr > EXPECTED
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "regexp subject search, punctuation"
+notmuch search subject:/\'X\'/ | notmuch_search_sanitize > OUTPUT
+cat <<EOF > EXPECTED
+thread:XXX   2009-11-18 [2/2] Keith Packard, Carl Worth; [notmuch] [PATCH] Make notmuch-show 'X' (and 'x') commands remove inbox (and unread) tags (inbox unread)
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "regexp subject search, no punctuation"
+notmuch search  subject:/X/ | notmuch_search_sanitize > OUTPUT
+cat <<EOF > EXPECTED
+thread:XXX   2009-11-18 [2/2] Keith Packard, Carl Worth; [notmuch] [PATCH] Make notmuch-show 'X' (and 'x') commands remove inbox (and unread) tags (inbox unread)
+thread:XXX   2009-11-18 [4/4] Jjgod Jiang, Alexander Botero-Lowry; [notmuch] Mac OS X/Darwin compatibility issues (inbox unread)
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "combine regexp from and subject"
+notmuch search  subject:/-C/ and from:/.an.k/ | notmuch_search_sanitize > OUTPUT
+cat <<EOF > EXPECTED
+thread:XXX   2009-11-17 [1/2] Jan Janak| Carl Worth; [notmuch] [PATCH] Older versions of install do not support -C. (inbox unread)
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "regexp error reporting"
+notmuch search 'from:/unbalanced[/' 1>OUTPUT 2>&1
+cat <<EOF > EXPECTED
+notmuch search: A Xapian exception occurred
+A Xapian exception occurred performing query: Invalid regular expression
+Query string was: from:/unbalanced[/
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_done