Up to now, the `SymbolGraphASTWalker` was only concerned with one module. This
change prepares for emitting multiple symbol graph files, for each module that
the module of interest extended. There is only one walker, so extract the
symbol logic into `SymbolGraph`, where it can be reused.
rdar://58941718
`pathComponents` doesn't help with disambiguation, so it shouldn't be a part of
the identifier, but can be moved up one level. Include an interface language in
the identifier instead.
rdar://problem/58853310
Add a platform kind and availability attributes for macCatalyst. macCatalyst
uses iOS version numbers and inherits availability from iOS attributes unless
a macCatalyst attribute is explicitly provided.
Adds a tool `swift-symbolgraph-extract` that reads an existing Swift
module and prints a platform- and language-agnostic JSON description of
the module, primarly for documentation.
Adds a small sub-library `SymbolGraphGen` which houses the core
implementation for collecting relevant information about declarations.
The main entry point is integrated directly into the driver as a mode:
the tool is meant to be run outside of the normal edit-compile-run/test
workflow to avoid impacting build times.
Along with common options for other tools, unique options include
`pretty-print` for debugging, and a `minimum-access-level` options for
including internal documentation.
A symbol graph is a directed graph where the nodes are symbols in a
module and the edges are relationships between them. For example, a
`struct S` may have a member `var x`. The graph would have two nodes for
`S` and `x`, and one "member-of" relationship edge. Other relationship
kinds include "inherits-from" or "conforms to". The data format for a
symbol graph is still under development and may change without notice
until a specificiation and versioning scheme is published.
Various aspects about a symbol are recorded in the nodes, such as
availability, documentation comments, or data needed for printing the
shapes of declarations without having to understand specifics about the
langauge.
Implicit and public-underscored stdlib declarations are not included by
default.
rdar://problem/55346798
