test_drc_chain_bridging_multipad.cpp

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/*
 * This program source code file is part of KiCad, a free EDA CAD application.
 *
 * Copyright The KiCad Developers, see AUTHORS.txt for contributors.
 *
 * 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 2
 * 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/>.
 */
 
#include <boost/test/unit_test.hpp>
 
#include <pcbnew_utils/board_file_utils.h>
 
#include <filesystem>
#include <fstream>
#include <string>
 
#include <board.h>
#include <board_design_settings.h>
#include <drc/drc_engine.h>
#include <drc/drc_item.h>
#include <netinfo.h>
#include <pcb_marker.h>
#include <pcbnew/pcb_io/kicad_sexpr/pcb_io_kicad_sexpr.h>
 
 
// These tests pin down the bridging-length contribution of multi-pad chain footprints
// in the matched-length DRC.  History:
//
// fd87668d29 introduced gather-then-skip behavior: any 3+ pad chain-member footprint
// silently contributed zero bridging length, which the comment block in the provider
// claimed to be guarding against.  MR review C-2 flagged that as the bug it was trying
// to prevent.
//
// Post C-2 fix the bridging contribution is the maximum pairwise cross-net pad span
// across the chain-member pads on the footprint.  This is the most generous (upper
// bound) bridge such a device could create, keeps the contribution non-zero, and
// scales identically to any pad count >= 2.
 
 
namespace
{
 
static const char* DRU_HEADER = "(version 1)\n";
 
 
std::string makeChainBudgetRule( const wxString& aName, const wxString& aMinMM,
                                 const wxString& aMaxMM )
{
    return wxString::Format( "%s(rule \"%s\"\n"
                             "    (condition \"A.NetClass == 'Default'\")\n"
                             "    (constraint net_chain_length (min %smm) (max %smm))\n"
                             ")\n",
                             DRU_HEADER, aName, aMinMM, aMaxMM )
            .ToStdString();
}
 
 
// Load a board from the test data dir, write a temp DRU file, run the matched-length DRC and
// return the count of DRCE_LENGTH_OUT_OF_RANGE markers raised on the chain "SIG".  Both nets
// named "/NET_*" are auto-tagged into chain "SIG".
size_t runChainLengthDrc( const std::string& aBoardFile, const std::string& aRuleText,
                          const std::string& aTmpSubdir )
{
    namespace fs = std::filesystem;
 
    fs::path tmpDir = fs::temp_directory_path() / aTmpSubdir;
    fs::create_directories( tmpDir );
 
    fs::path druPath = tmpDir / "chain_bridge.kicad_dru";
 
    {
        std::ofstream druOut( druPath );
        druOut << aRuleText;
    }
 
    PCB_IO_KICAD_SEXPR     plugin;
    std::unique_ptr<BOARD> board = plugin.LoadBoard( KI_TEST::GetPcbnewTestDataDir() + aBoardFile );
    board->BuildConnectivity();
 
    for( NETINFO_ITEM* net : board->GetNetInfo() )
    {
        if( net && net->GetNetname().StartsWith( wxS( "/NET_" ) ) )
            net->SetNetChain( wxS( "SIG" ) );
    }
 
    BOARD_DESIGN_SETTINGS& bds = board->GetDesignSettings();
 
    auto drcEngine = std::make_shared<DRC_ENGINE>( board.get(), &bds );
    wxFileName ruleFile( druPath.string() );
    drcEngine->InitEngine( ruleFile );
    bds.m_DRCEngine = drcEngine;
 
    bds.m_DRCSeverities[DRCE_INVALID_OUTLINE] = SEVERITY::RPT_SEVERITY_IGNORE;
    bds.m_DRCSeverities[DRCE_UNCONNECTED_ITEMS] = SEVERITY::RPT_SEVERITY_IGNORE;
    bds.m_DRCSeverities[DRCE_LIB_FOOTPRINT_ISSUES] = SEVERITY::RPT_SEVERITY_IGNORE;
    bds.m_DRCSeverities[DRCE_LIB_FOOTPRINT_MISMATCH] = SEVERITY::RPT_SEVERITY_IGNORE;
    bds.m_DRCSeverities[DRCE_DANGLING_VIA] = SEVERITY::RPT_SEVERITY_IGNORE;
    bds.m_DRCSeverities[DRCE_DRILL_OUT_OF_RANGE] = SEVERITY::RPT_SEVERITY_IGNORE;
    bds.m_DRCSeverities[DRCE_LENGTH_OUT_OF_RANGE] = SEVERITY::RPT_SEVERITY_ERROR;
 
    size_t lengthViolations = 0;
 
    drcEngine->SetViolationHandler(
            [&]( const std::shared_ptr<DRC_ITEM>& aItem, const VECTOR2I&, int,
                 const std::function<void( PCB_MARKER* )>& )
            {
                if( aItem->GetErrorCode() == DRCE_LENGTH_OUT_OF_RANGE )
                    ++lengthViolations;
            } );
 
    drcEngine->RunTests( EDA_UNITS::MM, true, false );
 
    std::error_code ec;
    fs::remove( druPath, ec );
 
    return lengthViolations;
}
 
}  // namespace
 
 
BOOST_AUTO_TEST_SUITE( DRCChainBridgingMultipad )
 
 
// 3-pad footprint, 2 nets (e.g. ferrite bead with centre tap).  Pads at x = -2.5, 0, +2.5.
// Nets A, A, B.  Track copper = 20 mm (10 mm on NET_A + 10 mm on NET_B).  Cross-net pad
// pairs span max 5 mm (-2.5 NET_A to +2.5 NET_B).  Total bridged chain = 25 mm.
BOOST_AUTO_TEST_CASE( ThreePadTwoNetFootprintContributesMaxPairwiseSpan )
{
    static const char* boardFile = "net_chains/chain_bridging_3pad_2net.kicad_pcb";
 
    // 26 mm budget passes (chain ~25 mm).
    size_t pass =
            runChainLengthDrc( boardFile, makeChainBudgetRule( "Pass", "0", "26" ),
                               "kicad_drc_chain_bridging_3pad_pass" );
    BOOST_CHECK_MESSAGE( pass == 0, "Expected no length violation under 26 mm budget, got "
                                            << pass );
 
    // 22 mm budget fails: pre-fix would silently drop bridging and report ~20 mm.  Post-fix
    // the 5 mm max pairwise span is included.
    size_t fail =
            runChainLengthDrc( boardFile, makeChainBudgetRule( "Fail", "0", "22" ),
                               "kicad_drc_chain_bridging_3pad_fail" );
    BOOST_CHECK_MESSAGE( fail == 1, "Expected one length violation under 22 mm budget, got "
                                            << fail );
}
 
 
// 3-pad footprint, 3 nets (transformer-style).  Pads at x = -2.5, 0, +2.5 on nets A, B, C.
// Track copper = 30 mm split evenly.  Max cross-net pairwise span = 5 mm.  Pre-fix the whole
// footprint was silently skipped because chainPads.size() > 2 broke the gather loop.
BOOST_AUTO_TEST_CASE( ThreePadThreeNetFootprintContributesMaxPairwiseSpan )
{
    static const char* boardFile = "net_chains/chain_bridging_3pad_3net.kicad_pcb";
 
    // Single T1 footprint gives 30 mm copper + 5 mm bridging = 35 mm.  Budget 36 mm passes.
    size_t pass =
            runChainLengthDrc( boardFile, makeChainBudgetRule( "Pass", "0", "36" ),
                               "kicad_drc_chain_bridging_3net_pass" );
    BOOST_CHECK_MESSAGE( pass == 0, "Expected no length violation under 36 mm budget, got "
                                            << pass );
 
    // 32 mm budget fails: pre-fix the 3-pad-3-net footprint was silently dropped (reporting
    // 30 mm copper).  Post-fix the 5 mm max pairwise span pushes total to 35 mm.
    size_t fail =
            runChainLengthDrc( boardFile, makeChainBudgetRule( "Fail", "0", "32" ),
                               "kicad_drc_chain_bridging_3net_fail" );
    BOOST_CHECK_MESSAGE( fail == 1, "Expected one length violation under 32 mm budget, got "
                                            << fail );
}
 
 
// 4-pad footprint, 2 nets (e.g. dual-winding chip with split netting).  Pads at
// x = -3, -1, +1, +3 on nets A, A, B, B.  Track copper = 20 mm.  Cross-net pad pairs:
// (-3 A, +1 B) = 4, (-3 A, +3 B) = 6, (-1 A, +1 B) = 2, (-1 A, +3 B) = 4.  Max = 6 mm.
BOOST_AUTO_TEST_CASE( FourPadFootprintContributesMaxPairwiseSpan )
{
    static const char* boardFile = "net_chains/chain_bridging_4pad.kicad_pcb";
 
    // Chain total: 20 mm copper + 6 mm bridging = 26 mm.  Budget 27 mm passes.
    size_t pass =
            runChainLengthDrc( boardFile, makeChainBudgetRule( "Pass", "0", "27" ),
                               "kicad_drc_chain_bridging_4pad_pass" );
    BOOST_CHECK_MESSAGE( pass == 0, "Expected no length violation under 27 mm budget, got "
                                            << pass );
 
    // 24 mm budget fails: pre-fix dropped bridging, post-fix adds 6 mm max pairwise span.
    size_t fail =
            runChainLengthDrc( boardFile, makeChainBudgetRule( "Fail", "0", "24" ),
                               "kicad_drc_chain_bridging_4pad_fail" );
    BOOST_CHECK_MESSAGE( fail == 1, "Expected one length violation under 24 mm budget, got "
                                            << fail );
}
 
 
// 3-pad footprint, single net.  All pads on NET_A.  No cross-net bridging; must contribute 0.
BOOST_AUTO_TEST_CASE( ThreePadSingleNetFootprintContributesZero )
{
    static const char* boardFile = "net_chains/chain_bridging_3pad_1net.kicad_pcb";
 
    // Pure copper sum is 20 mm with no bridging contribution.  Budget 21 mm passes.
    size_t pass =
            runChainLengthDrc( boardFile, makeChainBudgetRule( "Pass", "0", "21" ),
                               "kicad_drc_chain_bridging_singlenet_pass" );
    BOOST_CHECK_MESSAGE( pass == 0, "Single-net 3-pad footprint must not contribute bridging; "
                                    "got " << pass << " violations under 21 mm budget" );
}
 
 
BOOST_AUTO_TEST_SUITE_END()