Even without macros, it's useful for languages to have a format that's "readable without parsing", since new language versions can introduce keywords that break

Even without macros, it's useful for languages to have a format that's "readable without parsing", since new language versions can introduce keywords that break existing tooling. The worst case I experienced was a project to perform static analysis on Haskell code. Some optional features (e.g. LambdaCase) alter the way files must be parsed, and I recall at least one causing an ambiguity. This made parser libraries pretty useless, so I had to use the GHC compiler directly. This was around 2015, when GHC's API was much harder to use programatically; in particular it would often crash (saying "the impossible happened") if it wasn't given exactly the right "DynFlags". Those were hard to guess, so had to be passed through as commandline arguments, essentially re-creating the GHC command! Sometimes those features and flags are toggled in a "pragma" comment at the top of a file, but it is also very common for projects to specify these in a separate config file for the Cabal build system. Those files are a non-standard format, so we have to parse them using the Cabal library. Hence I ended up essentially re-implementing the Cabal command, as a way to pass the right arguments to my re-implemented GHC command. That still struggled to parse Haskell code, due to widespread use of the C preprocessor (CPP). I ended up using the vanilla GHC and Cabal commands, but added my own optimisation pass as a GHC plugin. This pass is a function accepting and returning "GHC Core" (one of GHC's intermediate representations); the only side-effects it permits are for error reporting. Hence my pass just returned its input unmodified, whilst also printing it to stderr (as s-expressions, for simplicity). This "GHC Core" representation was usable for my project, but I still find it incredible that I wasn't able to reliably parse Haskell code (especially given how well-suited Haskell is for parsing!).