Diagnostics

Core

• Clang diagnostics (errors, warnings, notes)

• Severity mapping (Error, Warning)

• Diagnostic ranges with source locations

• Related information (notes attached to diagnostics)

• File URI conversion for cross-file diagnostics

• Pull diagnostics model (textDocument/diagnostic) (clangd#2108)

• Report all missing #include errors, not just the first — the parser stops on the first fatal error

  #include "missing_a.h"  // error reported
  #include "missing_b.h"  // error NOT reported (parser already stopped)
  #include "missing_c.h"  // error NOT reported

• Show the full include chain for diagnostics originating in header files (clangd#1392)

  // current:  "In included file: expected ';'"
  // expected: "In main.cpp → utils.h → detail/impl.h: expected ';'"

• Reflect unsaved header file changes in diagnostics (clangd#488)

  // header.h (unsaved buffer): added new_func()
  // main.cpp: calls new_func() → should NOT show "undeclared identifier"

• Diagnostics for template instantiation errors in preamble headers (clangd#137)

Tags

• Deprecated tag for -Wdeprecated diagnostics
• Unnecessary tag for unused variable/parameter warnings

Publishing

• Push diagnostics on compilation completion
• Clear diagnostics on file close
• Per-file diagnostic grouping (interested file + headers)
• Diagnostic code field with Clang error codes
• codeDescription with links to Clang documentation
• Diagnostic source field distinguishing clang vs clang-tidy
• Configurable debounce delay before computing diagnostics (clangd#1471)
• Recompute diagnostics in open files when background indexing completes (clangd#2604)

Diagnostic Suppression

• // NOLINT comment suppression
• // NOLINTNEXTLINE comment suppression
• // NOLINTBEGIN / // NOLINTEND block suppression
• NOLINT for include-cleaner diagnostics (clangd#1982)
• Configurable severity per diagnostic category in config file (clangd#1937)
• Filter diagnostics by version control diff — only show warnings near changed lines (clangd#822)

Diagnostic Actions

• Automatic fix-its attached to diagnostics as code actions

Header Diagnostics

• Include-cleaner diagnostics for unused and missing #include directives

• Suppress false -Wunused-function for static inline functions in headers (clangd#1211)

  // utils.h
  static inline int helper() { return 42; }
  // should NOT warn "unused function" when checking header standalone

• Propagate -Wpadded and similar layout warnings from headers (clangd#1429)

• Suppress false -Wempty-translation-unit from preamble optimization (clangd#2358)

• Thread safety analysis across header boundaries (clangd#2386)

clang-tidy Integration

• clang-tidy diagnostics (gated by config)
• Suppress clang-tidy warnings originating in system-header macros (clangd#1587, clangd#2000)
• Clang static analyzer support (clangd#905)
• Version-specific clang-tidy documentation links (clangd#2136)
• Diagnostics for preprocessor directives that precede code (clangd#2501)

Diagnostic Display

• Correct diagnostic range for qualified type names — underline the full name, not just the base (clangd#1035)

  ns::Inner obj(42);
  //  ^^^^^ only base name underlined
  // should underline "ns::Inner"

• Show optimization remarks (-Rpass) as diagnostics (clangd#2519)

• Project-wide warning listing (clangd#1973)

Config File Diagnostics

• Report diagnostics for malformed .clang-tidy and .clang-format files (clangd#2313, clangd#2591)

Diagnostic Correctness

Known issues that should be handled correctly:

• Macro redefinition warning pointing to the same location (clangd#2479)
• Wrong -Wmissing-braces fix suggestion for nested array initialization (clangd#2434)
• Invalid severity 0 when preamble invalidation mixes diagnostic messages (clangd#2124)
• Undeclared identifier diagnostic hidden by correction-related diagnostics (clangd#547)
• Misleading downstream diagnostics when --include file is missing (clangd#2229)

Changelog

Date	Change	PR
—	Clang diagnostics, severity mapping, tags, push publishing	—