[PATCH] Fix JSON compilation database command unescaping.

[Manuel Klimek]

On Mon Nov 24 2014 at 10:57:12 AM Daniel Cheng <dcheng at google.com> wrote:

> I abandoned the previous diff, because I was flailing about the interface
> and had no idea what I was doing.
>
> As for the fix, the JSON compilation database spec (
> http://clang.llvm.org/docs/JSONCompilationDatabase.html) says:
> > Parameters use shell quoting and shell escaping of quotes.
>
> The problem is that `skipEscapeCharacter()` always skips over a backslash
> character, instead of the behavior described in the spec (only shell
> escaping of quotes). Ninja and CMake expect that shell escaping is only
> applied to quotes, and output compile database commands like:
> ```"clang-cl.exe path\\to\\input.cc"```
>
> After JSON unescaping, the command looks like:
> ```clang-cl.exe path\to\input.cc```
>
> But because the argument parser always skips backslashes,
> `JSONCompilationDatabase::getCompileCommands` ends up returning:
> ```clang-cl.exe pathtoinput.cc```
>
> Which obviously doesn't work. One alternative is to decide that all normal
> shell escapes apply and change the spec. This has one big disadvantage: the
> JSON decoder already turns escape sequences into their special character
> (e.g. `\n` to an actual newline character). Why does the argument unescaper
> need to do the same thing?
>
> Finally, there were no tests for the command argument unescaping behavior,
> so I modified `JSONCompilationDatabase.GetAl


What about these?
http://reviews.llvm.org/diffusion/L/browse/cfe/trunk/unittests/Tooling/CompilationDatabaseTest.cpp;222646$294



> lCompileCommands` to cover several argument parser behaviors:
> - Double quotes allow spaces to be included in a single argument.
> - Escaped quotes are skipped over inside a double quoted argument.
> - Backslashes are included in the unescaped argument if they weren't
> escaping a quote.
> - Backslashes are allowed as the last character of a single argument.
>
> http://reviews.llvm.org/D6376
>
>
>
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