Add initial support for parsing patterns into parse trees

Introduce a parser for patterns that generates a parse tree. The
language understood by the parser is:

pattern = '?'TERM
        | '?'TERM '(' pattern (',' pattern)* ','? ')'
        | WORD
        | QUOTED-WORD
TERM    = [0-9a-zA-Z-]
WORD    = [0-9a-ZA-Z-.*^$\[\]_\\]
QUOTED_WORD = "..."		# you know what I mean

This language is context free, which is a massive simplification
from aptitude's language, where ?foo(bar) could have two different
meanings depending on whether ?foo takes an argument or not.

1 files changed, 95 insertions, 0 deletions

diff --git a/test/libapt/pattern_test.cc b/test/libapt/pattern_test.cc
new file mode 100644
index 000000000..de2fbceb9
--- /dev/null
+++ b/test/libapt/pattern_test.cc
@@ -0,0 +1,95 @@
+/*
+ * cachefilter-patterns.h - Pattern parser and additional patterns as matchers
+ *
+ * Copyright (c) 2019 Canonical Ltd
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#include <config.h>
+#include <apt-pkg/cachefilter-patterns.h>
+#include <apt-pkg/cachefilter.h>
+
+#include <gtest/gtest.h>
+
+using namespace APT::Internal;
+
+TEST(TreeParserTest, ParseWord)
+{
+   auto node = PatternTreeParser("word").parseTop();
+   auto wordNode = dynamic_cast<PatternTreeParser::WordNode *>(node.get());
+
+   EXPECT_EQ(node.get(), wordNode);
+   EXPECT_EQ(wordNode->word, "word");
+}
+
+TEST(TreeParserTest, ParseQuotedWord)
+{
+   auto node = PatternTreeParser("\"a word\"").parseTop();
+   auto wordNode = dynamic_cast<PatternTreeParser::WordNode *>(node.get());
+
+   EXPECT_EQ(node.get(), wordNode);
+   EXPECT_EQ(wordNode->word, "a word");
+}
+
+TEST(TreeParserTest, ParsePattern)
+{
+   auto node = PatternTreeParser("?hello").parseTop();
+   auto patternNode = dynamic_cast<PatternTreeParser::PatternNode *>(node.get());
+
+   EXPECT_EQ(node.get(), patternNode);
+   EXPECT_EQ(patternNode->term, "?hello");
+   EXPECT_TRUE(patternNode->arguments.empty());
+   EXPECT_FALSE(patternNode->haveArgumentList);
+}
+
+TEST(TreeParserTest, ParseWithEmptyArgs)
+{
+   auto node = PatternTreeParser("?hello()").parseTop();
+   auto patternNode = dynamic_cast<PatternTreeParser::PatternNode *>(node.get());
+
+   EXPECT_EQ(node.get(), patternNode);
+   EXPECT_EQ(patternNode->term, "?hello");
+   EXPECT_TRUE(patternNode->arguments.empty());
+   EXPECT_TRUE(patternNode->haveArgumentList);
+}
+
+TEST(TreeParserTest, ParseWithOneArgs)
+{
+   auto node = PatternTreeParser("?hello(foo)").parseTop();
+   auto patternNode = dynamic_cast<PatternTreeParser::PatternNode *>(node.get());
+
+   EXPECT_EQ(node.get(), patternNode);
+   EXPECT_EQ(patternNode->term, "?hello");
+   EXPECT_EQ(1u, patternNode->arguments.size());
+}
+
+TEST(TreeParserTest, ParseWithManyArgs)
+{
+   auto node = PatternTreeParser("?hello(foo,bar)").parseTop();
+   auto patternNode = dynamic_cast<PatternTreeParser::PatternNode *>(node.get());
+
+   EXPECT_EQ(node.get(), patternNode);
+   EXPECT_EQ(patternNode->term, "?hello");
+   EXPECT_EQ(2u, patternNode->arguments.size());
+}
+
+TEST(TreeParserTest, ParseWithManyArgsWithSpaces)
+{
+   auto node = PatternTreeParser("?hello (foo, bar)").parseTop();
+   auto patternNode = dynamic_cast<PatternTreeParser::PatternNode *>(node.get());
+
+   EXPECT_EQ(node.get(), patternNode);
+   EXPECT_EQ(patternNode->term, "?hello");
+   EXPECT_EQ(2u, patternNode->arguments.size());
+}
+
+TEST(TreeParserTest, ParseWithManyArgsWithSpacesWithTrailingComma)
+{
+   auto node = PatternTreeParser("?hello (foo, bar,)").parseTop();
+   auto patternNode = dynamic_cast<PatternTreeParser::PatternNode *>(node.get());
+
+   EXPECT_EQ(node.get(), patternNode);
+   EXPECT_EQ(patternNode->term, "?hello");
+   EXPECT_EQ(2u, patternNode->arguments.size());
+}