Suggest valid options when the configuration contains unknown keys

This changeset is purely to improve the user experience. When the
configuration parsing fails with an unknown key we'll test all possible
keys and suggest one that looks a lot like it. This will be nice for
people that make simple typos.

CMakeLists.txt

@@ -134,9 +134,11 @@ add_executable(flashmq
     globber.cpp
     x509manager.h x509manager.cpp
     backgroundworker.h backgroundworker.cpp
-
+    edlib/src/edlib.cpp
     )
 
+target_include_directories(flashmq PRIVATE edlib/include)
+
 target_link_libraries(flashmq pthread dl ssl crypto resolv anl)
 
 execute_process(COMMAND ../.get-os-codename-and-stamp.sh OUTPUT_VARIABLE OS_CODENAME)

FlashMQTests/CMakeLists.txt

@@ -152,6 +152,7 @@ add_executable(flashmq-tests
     ../x509manager.cpp
     ../backgroundworker.h ../backgroundworker.cpp
     ../flashmqtestclient.cpp ../flashmqtestclient.h
+    ../edlib/src/edlib.cpp
     main.cpp
     mainappinthread.h mainappinthread.cpp
     maintests.h maintests.cpp
@@ -171,6 +172,8 @@ add_executable(flashmq-tests
 
     )
 
+target_include_directories(flashmq-tests PRIVATE ../edlib/include)
+
 target_include_directories(flashmq-tests PUBLIC ..)
 
 target_link_libraries(flashmq-tests pthread dl ssl crypto resolv anl)

FlashMQTests/configtests.cpp

@@ -117,3 +117,44 @@ void MainTests::test_parsing_numbers()
         }
     }
 }
+
+void MainTests::test_config_suggestion()
+{
+    // User made a small typo: 'session' instead of 'sessions'
+    {
+        ConfFileTemp config;
+        config.writeLine("expire_session_after_seconds 180");
+        config.closeFile();
+
+        ConfigFileParser parser(config.getFilePath());
+
+        try
+        {
+            parser.loadFile(false);
+            FMQ_FAIL("The parser is too liberal");
+        }
+        catch (ConfigFileException &ex)
+        {
+            FMQ_COMPARE(ex.what(), "Config key 'expire_session_after_seconds' is not valid (here). Did you mean: expire_sessions_after_seconds ?");
+        }
+    }
+
+    // User entered gibberish. Let's not suggest gibberish back
+    {
+        ConfFileTemp config;
+        config.writeLine("foobarbaz 180");
+        config.closeFile();
+
+        ConfigFileParser parser(config.getFilePath());
+
+        try
+        {
+            parser.loadFile(false);
+            FMQ_FAIL("The parser is too liberal");
+        }
+        catch (ConfigFileException &ex)
+        {
+            FMQ_COMPARE(ex.what(), "Config key 'foobarbaz' is not valid (here).");
+        }
+    }
+}

FlashMQTests/maintests.cpp

@@ -223,6 +223,7 @@ MainTests::MainTests()
     REGISTER_FUNCTION(testOverrideWillDelayOnSessionDestructionByTakeOver);
     REGISTER_FUNCTION(testDisabledWills);
     REGISTER_FUNCTION(testMqtt5DelayedWillsDisabled);
+    REGISTER_FUNCTION(test_config_suggestion);
     REGISTER_FUNCTION(testIncomingTopicAlias);
     REGISTER_FUNCTION(testOutgoingTopicAlias);
     REGISTER_FUNCTION(testOutgoingTopicAliasStoredPublishes);

FlashMQTests/maintests.h

@@ -120,6 +120,7 @@ class MainTests
     void testOverrideWillDelayOnSessionDestructionByTakeOver();
     void testDisabledWills();
     void testMqtt5DelayedWillsDisabled();
+    void test_config_suggestion();
 
 
     void testIncomingTopicAlias();

FlashMQTests/testhelpers.cpp

@@ -1,6 +1,7 @@
 #include "testhelpers.h"
 
 #include <iostream>
+#include <cstring>
 
 int assert_count;
 int assert_fail_count;
@@ -16,8 +17,21 @@ bool fmq_assert(bool b, const char *failmsg, const char *actual, const char *exp
 
         if (asserts_print)
         {
-            std::cout << RED << "FAIL" << COLOR_END << ": '" << failmsg << "', " << actual << " != " << expected << std::endl
-                      << " in " << file << ", line " << line << std::endl;
+            // There are two types of failmsg: unformatted ones and formatted ones.
+            // By testing for a newline we can detect formatted ones.
+            if (strchr(failmsg, '\n') == nullptr)
+            {
+                // unformatted
+                std::cout << RED << "FAIL" << COLOR_END << ": '" << failmsg << "', " << actual << " != " << expected << std::endl
+                          << " in " << file << ", line " << line << std::endl;
+            }
+            else
+            {
+                // formatted
+                std::cout << RED << "FAIL" << COLOR_END << " in " << file << ", line " << line << std::endl;
+                std::cout << failmsg << std::endl;
+                std::cout << "Comparison: " << actual << " != " << expected << std::endl;
+            }
         }
     }
 

FlashMQTests/testhelpers.h

@@ -61,7 +61,17 @@ inline bool fmq_compare(const char *c1, const char *c2, const char *actual, cons
     std::string s2(c2);
 
     std::ostringstream oss;
-    oss << s1 << " != " << s2;
+
+    if (s1.length() + s2.length() < 100)
+    {
+        // short form
+        oss << s1 << " != " << s2;
+    }
+    else
+    {
+        oss << "Actual:     " << s1 << std::endl;
+        oss << "Expected:   " << s2;
+    }
 
     return fmq_assert(s1 == s2, oss.str().c_str(), actual, expected, file, line);
 }

FlashMQTests/willtests.cpp

@@ -2,6 +2,7 @@
 #include "testhelpers.h"
 #include "flashmqtestclient.h"
 #include "conffiletemp.h"
+#include "exceptions.h"
 
 void MainTests::testMqtt3will()
 {

configfileparser.cpp

@@ -23,6 +23,7 @@ See LICENSE for license details.
 #include "exceptions.h"
 #include "utils.h"
 #include "globber.h"
+#include "edlib.h"
 
 /**
  * @brief Like std::stoi, but demands that the entire value is consumed
@@ -93,6 +94,32 @@ bool ConfigFileParser::testKeyValidity(const std::string &key, const std::string
     {
         std::ostringstream oss;
         oss << "Config key '" << key << "' is not valid (here).";
+
+        // Maybe the user made a typo
+        EdlibAlignConfig cmpcnf = edlibDefaultAlignConfig();
+        const std::string *alternative = nullptr;
+        int alternative_distance = INT_MAX;
+
+        for (const std::string &possible_key : validKeys)
+        {
+            EdlibAlignResult result = edlibAlign(key.c_str(), key.length(), possible_key.c_str(), key.length(), cmpcnf);
+            if (result.status == EDLIB_STATUS_OK)
+            {
+                // The mathemathical formula "x/y < 0.5"
+                // can be approximated with integers as "x*2/y < 1"
+                if ((result.editDistance * 2) / key.length() < 1 && result.editDistance < alternative_distance)
+                {
+                    alternative = &possible_key;
+                    alternative_distance = result.editDistance;
+                }
+            }
+            edlibFreeAlignResult(result);
+        }
+        if (alternative != nullptr)
+        {
+            oss << " Did you mean: " << alternative->c_str() << " ?";
+        }
+
         throw ConfigFileException(oss.str());
     }
 

edlib/LICENSE

@@ -0,0 +1,20 @@
+The MIT License (MIT)
+
+Copyright (c) 2014 Martin Šošić
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

edlib/README

@@ -0,0 +1 @@
+Local copy of https://github.com/Martinsos/edlib