clice/openspec/changes/explore-improve-folding-range-support/comparison.md

Downloaded Upstream Reference

Downloaded from GitHub tag llvmorg-21.1.8 into openspec/changes/explore-improve-folding-range-support/reference/clangd/llvmorg-21.1.8/ using curl.

Files downloaded:

• clang-tools-extra/clangd/SemanticSelection.cpp
• clang-tools-extra/clangd/SemanticSelection.h
• clang-tools-extra/clangd/ClangdServer.cpp
• clang-tools-extra/clangd/ClangdServer.h
• clang-tools-extra/clangd/ClangdLSPServer.cpp
• clang-tools-extra/clangd/Protocol.h
• clang-tools-extra/clangd/Protocol.cpp
• clang-tools-extra/clangd/test/folding-range.test
• clang-tools-extra/clangd/unittests/SemanticSelectionTests.cpp

Raw GitHub URLs used:

• https://raw.githubusercontent.com/llvm/llvm-project/llvmorg-21.1.8/clang-tools-extra/clangd/SemanticSelection.cpp
• https://raw.githubusercontent.com/llvm/llvm-project/llvmorg-21.1.8/clang-tools-extra/clangd/SemanticSelection.h
• https://raw.githubusercontent.com/llvm/llvm-project/llvmorg-21.1.8/clang-tools-extra/clangd/ClangdServer.cpp
• https://raw.githubusercontent.com/llvm/llvm-project/llvmorg-21.1.8/clang-tools-extra/clangd/ClangdServer.h
• https://raw.githubusercontent.com/llvm/llvm-project/llvmorg-21.1.8/clang-tools-extra/clangd/ClangdLSPServer.cpp
• https://raw.githubusercontent.com/llvm/llvm-project/llvmorg-21.1.8/clang-tools-extra/clangd/Protocol.h
• https://raw.githubusercontent.com/llvm/llvm-project/llvmorg-21.1.8/clang-tools-extra/clangd/Protocol.cpp
• https://raw.githubusercontent.com/llvm/llvm-project/llvmorg-21.1.8/clang-tools-extra/clangd/test/folding-range.test
• https://raw.githubusercontent.com/llvm/llvm-project/llvmorg-21.1.8/clang-tools-extra/clangd/unittests/SemanticSelectionTests.cpp

Clice Reference Files

Current branch files compared against:

• src/feature/folding_ranges.cpp
• src/server/master_server.cpp
• tests/unit/feature/folding_range_tests.cpp

Confirmed Comparison Findings

1. clangd already has dedicated comment folding and line-only rendering

clangd's pseudo-parser folding path in SemanticSelection.cpp explicitly handles:

• bracket folds with line-only adjustment at SemanticSelection.cpp:223-235
• multiline block and contiguous comment-group folds at SemanticSelection.cpp:238-269

The request path wires LineFoldingOnly from client capabilities in:

• ClangdLSPServer.cpp:545
• ClangdServer.cpp:967-980

Regression coverage exists in:

• test/folding-range.test:6-20
• unittests/SemanticSelectionTests.cpp:269-455

Current clice does not have any comment collector in src/feature/folding_ranges.cpp, and the server request path in src/server/master_server.cpp:517-525 forwards folding requests without any folding-specific options.

2. clice already folds more AST structure than clangd

clangd's AST-oriented getFoldingRanges(ParsedAST &AST) is intentionally narrow and only walks syntax-tree compound statements in SemanticSelection.cpp:170-175.

Current clice already folds:

• namespaces at src/feature/folding_ranges.cpp:66-80
• records and access-specifier regions at src/feature/folding_ranges.cpp:82-121
• function parameter lists and bodies at src/feature/folding_ranges.cpp:123-144, 246-269
• lambda captures at src/feature/folding_ranges.cpp:134-143
• call argument lists at src/feature/folding_ranges.cpp:146-179
• initializer lists at src/feature/folding_ranges.cpp:181-185
• compound statements at src/feature/folding_ranges.cpp:271-284

That is materially broader than clangd's current AST folding baseline.

3. clice still exposes richer but less compatible output

Current clice maps many internal categories directly to custom kind strings in src/feature/folding_ranges.cpp:35-54, and carries collapsed_text through src/feature/folding_ranges.cpp:56-60 and src/feature/folding_ranges.cpp:363-376.

clangd's downloaded protocol reference exposes only folding kinds in Protocol.h:1970-1981 and serializes them in Protocol.cpp:1680-1692. The downloaded clangd protocol does not expose collapsedText, so collapsedText is a clice-specific protocol improvement rather than a clangd parity requirement.

4. clice still has an incomplete #endif branch closure bug

Current clice closes a prior conditional branch only when #else is seen at src/feature/folding_ranges.cpp:302-311. On #endif, it only pops the stack at src/feature/folding_ranges.cpp:314-317 and emits no range for the final branch body.

clangd does not solve this either. Upstream SemanticSelection.cpp:178-190 still leaves PP conditional regions and disabled regions as FIXME items. This means #if branch folding remains a clice extension opportunity, not a direct clangd parity target.

5. clice lacks client-capability plumbing for folding

Current clice only advertises caps.folding_range_provider = true in src/server/master_server.cpp:244, and the request handler in src/server/master_server.cpp:517-525 forwards no lineFoldingOnly, rangeLimit, or collapsedText support signals into the feature layer.

clangd at least threads LineFoldingOnly from the client into folding generation via ClangdLSPServer.cpp:545 and ClangdServer.cpp:974-976.

6. clice test coverage is still weaker in the most important gap areas

Current clice has structural tests, but the directive and pragma-region cases remain placeholder-only in tests/unit/feature/folding_range_tests.cpp:398-430. The tests also do not assert folding kinds.

clangd's downloaded tests cover:

• AST folding
• comment folding
• line-folding-only behavior
• macro-related exclusion cases

Those are visible in unittests/SemanticSelectionTests.cpp:269-455.

Planning Implications

The downloaded source narrows the real parity target:

• confirmed clangd parity gaps for clice: comment folding, lineFoldingOnly, standard public kind behavior, stronger tests
• confirmed clice advantages over clangd: namespaces, access-specifier regions, lambda captures, function parameter folds, function-call folds, initializer folds, pragma regions, collapsed text
• confirmed clice-specific extension space beyond clangd: inactive-branch folding, complete #if/#elif/#else/#endif folding, macro-definition folding, include/import grouping

The earlier third_party vendor plan was the wrong storage model for this branch. The correct model is a change-local downloaded reference under openspec/changes/explore-improve-folding-range-support/reference/.