Re: IDE

[Dmitry Gutov]

Hi Eric,

On 10/10/2015 07:48 PM, Eric Ludlam wrote:

> I had always intended CEDET to be a baseline for IDE like features.
> Looking just at tagging files, those familiar with it's internals
> recognize that it can use external tools as weak as ctags or GLOBAL, and
> can use a more powerful external tool for parsing as well, such as using
> JAVAC for decompiling .jar files into tags.

It sounds good if all I have is a parser/tagger.

But if I already have an external tool that can give me a set of 
completions at a given position in a given buffer, and also provides a 
go-to-definition feature, what's the advantage of going through 
Semantic? SRecode support?

Not to mention that we have tools like Jedi that only (mostly) do these 
two things, but don't provide dumps of the syntax tree.

> As a backup, it also has
> in-buffer parsing for when you've only half-written your code, or when
> no external tool is available.

That assumes we also have a Semantic grammar for the said language. And 
then, we'll need to duplicate whatever logic is used by the external 
tool to disambiguate between same-named methods in different classes.

If that's even possible.

> The same philosophy is throughout CEDET.  Unfortunately, those who are
> interested in tooling who brush casually past CEDET only see that people
> complain that it doesn't always complete right, or that the C++ part is
> hard to setup

The example we've been given in one of the previous discussions of C++ 
support is that Semantic can't tell the difference between different 
methods with the same name? If Z#foo returns type A, and T#foo returns 
type B, it's been shown that Semantic doesn't know which is the type 
'x.foo'.

Given this, how would we expect it to properly support languages with 
type inference like Scala or Go? Not to mention dynamic languages which 
normally have no type annotations on methods, and often use more 
complicated algorithms for accurate code completion.

> If we look at the two starting key features listed for IDEs,
> "completion" and "refactoring", the basics are all there.  CEDET has a
> completion engine, but it is only as good as the input data.

It's limited by the input data, sure, but it also has to know what to do 
with it.

If only implementing accurate code completion was as easy as writing a 
language parser.

> CEDET also has 'srecode' which is about
> generating code.  This bit is trickier, as the intention is you could
> write one highlevel tool that might extract tag data from your file,
> permute the language-independent tags, and then write them back out with
> srecode.  There are tests showing this working, but they are simple and
> proof of concept and not stuff someone would depend on day-to-day.

SRecode should be in a better position, but I imagine it would also fail 
often enough in dynamic languages.

And in any case, one has to teach Semantic about scoping rules for each 
given language, for SRecode to only rename, say, a variable 'foo' but 
not function 'foo', or only the variable 'bar', but not the variable 
'bar' up the scope that's being shadowed.