Cache lines in Lexer and show original input when running into an error

test/ZoneCodeGeneratorLibTests/Parsing/Impl/IncludingStreamProxyTest.cpp

@@ -133,4 +133,49 @@ namespace test::parsing::impl::including_stream_proxy
 
         REQUIRE(proxy.Eof());
     }
+
+    TEST_CASE("IncludingStreamProxy: Ensure pragma once prevents including the same file more than once", "[parsing][parsingstream]")
+    {
+        const std::vector<std::string> lines
+        {
+            "Hello world",
+            "#include \"ASDF.txt\"",
+            "#include \"ASDF.txt\"",
+            "and bye"
+        };
+
+        const std::vector<std::string> asdf
+        {
+            "#pragma once",
+            "Hello galaxy"
+        };
+
+        MockParserLineStream mockStream(lines);
+        mockStream.AddIncludeLines("ASDF.txt", asdf);
+
+        IncludingStreamProxy proxy(&mockStream);
+
+        {
+            auto line = proxy.NextLine();
+            REQUIRE(line.m_line_number == 1);
+            REQUIRE(line.m_filename.get() == MockParserLineStream::MOCK_FILENAME);
+            REQUIRE(line.m_line == "Hello world");
+        }
+
+        {
+            auto line = proxy.NextLine();
+            REQUIRE(line.m_line_number == 2);
+            REQUIRE(line.m_filename.get() == "ASDF.txt");
+            REQUIRE(line.m_line == "Hello galaxy");
+        }
+
+        {
+            auto line = proxy.NextLine();
+            REQUIRE(line.m_line_number == 4);
+            REQUIRE(line.m_filename.get() == MockParserLineStream::MOCK_FILENAME);
+            REQUIRE(line.m_line == "and bye");
+        }
+
+        REQUIRE(proxy.Eof());
+    }
 }

test/ZoneCodeGeneratorLibTests/Parsing/Mock/MockParserLineStream.cpp

@@ -50,6 +50,12 @@ bool MockParserLineStream::IncludeFile(const std::string& filename)
     return true;
 }
 
+void MockParserLineStream::PopCurrentFile()
+{
+    if (!m_include_positions.empty())
+        m_include_positions.pop_back();
+}
+
 bool MockParserLineStream::IsOpen() const
 {
     return true;

test/ZoneCodeGeneratorLibTests/Parsing/Mock/MockParserLineStream.h

@@ -30,6 +30,7 @@ public:
     void AddIncludeLines(const std::string& filename, const std::vector<std::string>& lines);
     ParserLine NextLine() override;
     bool IncludeFile(const std::string& filename) override;
+    void PopCurrentFile() override;
     _NODISCARD bool IsOpen() const override;
     _NODISCARD bool Eof() const override;
 };