Otherwise they may have module dependencies of their own which will not be detected by the scanner and included in the list of explicit inputs for compilation.
When prefix mapping paths that are used in clang, ensure we are
consistently using the same prefix mapper from clang. This prevents
mismatches that could cause modules to fail to load.
rdar://123324072
The code, previously, only properly handled such dependencies being a distinct category for Swift source and Swift textual dependency infos. Swift binary module dependencies must handle this similarly and this change adds the missing support for them. Recent refactor of the scanner also means that now Swift binary dependencies with Swift overlay dependencies may crash the scanner, and this change resolves this as well.
Resolves rdar://117088840
dependencies
It is valuable for clients to be able to distinguish which dependencies of a
Swift module originated from 'import' statements, and which ones are implicit
dependency Swift overlays of imported Clang modules.
Teach swift dependency scanner to use CAS to capture the full dependencies for a build and construct build commands with immutable inputs from CAS.
This allows swift compilation caching using CAS.
Instead of being a part of 'directDependencies' on a module dependency info, make them a separate array of dependency IDs for Swift Source and Textual modules.
This will allow clients to still distinguish direct module dependencies imported from a given module, versus dependencies added because direct/transitive Clang module dependencies have Swift overlays.
This change does *not* remove overlay dependencies from 'directDependencies' yet, just adds them as a separate field on the module details info. A followup change will remove overlay and bridging header dependencies from 'directDependencies' once the clients have had a chance to adopt to this change.
Using a virutal output backend to capture all the outputs from
swift-frontend invocation. This allows redirecting and/or mirroring
compiler outputs to multiple location using different OutputBackend.
As an example usage for the virtual outputs, teach swift compiler to
check its output determinism by running the compiler invocation
twice and compare the hash of all its outputs.
Virtual output will be used to enable caching in the future.
This changes the scanner's behavior to "resolve" a discovered module's dependencies to a set of Module IDs: module name + module kind (swift textual, swift binary, clang, etc.).
The 'ModuleDependencyInfo' objects that are stored in the dependency scanner's cache now carry a set of kind-qualified ModuleIDs for their dependencies, in addition to unqualified imported module names of their dependencies.
Previously, the scanner's internal state would cache a module dependnecy as having its own set of dependencies which were stored as names of imported modules. This led to a design where any time we needed to process the dependency downstream from its discovery (e.g. cycle detection, graph construction), we had to query the ASTContext to resolve this dependency's imports, which shouldn't be necessary. Now, upon discovery, we "resolve" a discovered dependency by executing a lookup for each of its imported module names (this operation happens regardless of this patch) and store a fully-resolved set of dependencies in the dependency module info.
Moreover, looking up a given module dependency by name (via `ASTContext`'s `getModuleDependencies`) would result in iterating over the scanner's module "loaders" and querying each for the module name. The corresponding modules would then check the scanner's cache for a respective discovered module, and if no such module is found the "loader" would search the filesystem.
This meant that in practice, we searched the filesystem on many occasions where we actually had cached the required dependency, as follows:
Suppose we had previously discovered a Clang module "foo" and cached its dependency info.
-> ASTContext.getModuleDependencies("foo")
--> (1) Swift Module "Loader" checks caches for a Swift module "foo" and doesn't find one, so it searches the filesystem for "foo" and fails to find one.
--> (2) Clang Module "Loader" checks caches for a Clang module "foo", finds one and returns it to the client.
This means that we were always searching the filesystem in (1) even if we knew that to be futile.
With this change, queries to `ASTContext`'s `getModuleDependencies` will always check all the caches first, and only delegate to the scanner "loaders" if no cached dependency is found. The loaders are then no longer in the business of checking the cached contents.
To handle cases in the scanner where we must only lookup either a Swift-only module or a Clang-only module, this patch splits 'getModuleDependencies' into an alrady-existing 'getSwiftModuleDependencies' and a newly-added 'getClangModuleDependencies'.
Introduces a concept of a dependency scanning action context hash, which is used to select an instance of a global dependency scanning cache which gets re-used across dependency scanning actions.
Doing so will allow clients to know which Swift-specific PCM arguments are already captured from the scan that first discovered this module.
SwiftDriver, in particular, will be able to use this information to avoid re-scanning a given Clang module if the initial scan was sufficient for all possible sets of PCM arguments on Swift modules that depend on said Clang module.
And only resolve cached dependencies that came from scanning actions with the same target triple.
This change means that the `GlobalModuleDependenciesCache` must be configured with a specific target triple for every scannig action, and it will only resolve previously-found dependencies from previous scannig actions using the exact same triple.
Furthermore, the `GlobalModuleDependenciesCache` separately tracks source-file-based module dependencies as those represent main Swift modules of previous scanning actions, and we must be able to resolve those regardless of the target triple.
Resolves rdar://83105455
These kinds of modules differ from `SwiftTextual` modules in that they do not have an interface and have source-files.
It is cleaner to enforce this distinction with types, instead of checking for interface optionality everywhere.
This change causes the cache to be layered with a local "cache" that wraps the global cache, which will serve as the source of truth. The local cache persists only for the duration of a given scanning action, and has a store of references to dependencies resolved as a part of the current scanning action only, while the global cache is the one that persists across scanning actions (e.g. in `DependencyScanningTool`) and stores actual module dependency info values.
Only the local cache can answer dependency lookup queries, checking current scanning action results first, before falling back to querying the global cache, with queries disambiguated by the current scannning action's search paths, ensuring we never resolve a dependency lookup query with a module info that could not be found in the current action's search paths.
This change is required because search-path disambiguation can lead to false-negatives: for example, the Clang dependency scanner may find modules relative to the compiler's path that are not on the compiler's direct search paths. While such false-negative query responses should be functionally safe, we rely on the current scanning action's results being always-present-in-the-cache for the scanner's functionality. This layering ensures that the cache use-sites remain unchanged and that we get both: preserved global state which can be queried disambiguated with the search path details, and an always-consistent local (current action) cache state.
