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-rw-r--r-- | docs/YamlIO.rst | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/docs/YamlIO.rst b/docs/YamlIO.rst index 5ec0a01f8d..46609a3acd 100644 --- a/docs/YamlIO.rst +++ b/docs/YamlIO.rst @@ -647,6 +647,44 @@ mappings, as long as they are convertable. To check a tag, inside your mapping() method you can use io.mapTag() to specify what the tag should be. This will also add that tag when writing yaml. +Validation +---------- + +Sometimes in a yaml map, each key/value pair is valid, but the combination is +not. This is similar to something having no syntax errors, but still having +semantic errors. To support semantic level checking, YAML I/O allows +an optional ``validate()`` method in a MappingTraits template specialization. + +When parsing yaml, the ``validate()`` method is call *after* all key/values in +the map have been processed. Any error message returned by the ``validate()`` +method during input will be printed just a like a syntax error would be printed. +When writing yaml, the ``validate()`` method is called *before* the yaml +key/values are written. Any error during output will trigger an ``assert()`` +because it is a programming error to have invalid struct values. + + +.. code-block:: c++ + + using llvm::yaml::MappingTraits; + using llvm::yaml::IO; + + struct Stuff { + ... + }; + + template <> + struct MappingTraits<Stuff> { + static void mapping(IO &io, Stuff &stuff) { + ... + } + static StringRef validate(IO &io, Stuff &stuff) { + // Look at all fields in 'stuff' and if there + // are any bad values return a string describing + // the error. Otherwise return an empty string. + return StringRef(); + } + }; + Sequence ======== |