Improve tests to call python script through python executable. Even this
doesn't cause any errors now, it will be a problem for future when we
run CAS tests on Windows platform. Clean up the current test to avoid
bad test example.
The code of `ScanDependencies.cpp` was creating invalid JSON since #66031
because in the case of having `extraPcmArgs` and `swiftOverlayDependencies`,
but not `bridgingHeader`, a comma will not be added at the end of
`extraPcmArgs`, creating an invalid JSON file. Additionally that same PR
added a trailing comma at the end of the `swiftOverlayDependencies`, which
valid JSON does not allow, but that bug was removed in #66366.
Both problems are, however, present in the 5.9 branch, because #66936
included #66031, but not #66366.
Besides fixing the problem in `ScanDependencies.cpp` I modified every test
that uses `--scan-dependencies` to pass the produced JSON through
Python's `json.tool` in order to validate proper JSON is produced. In
most cases I was able to pipe the output of the tool into `FileCheck`,
but in some cases the validation is done by itself because the checks
depend on the exact format generated by `--scan-dependencies`. In
a couple of tests I added a call to `FileCheck` that seemed to be
missing.
Without these changes, two tests seems to be generating invalid JSON in
my machine:
- `ScanDependencies/local_cache_consistency.swift` (which outputs `Expecting ',' delimiter: line 525 column 11 (char 22799)`)
- `ScanDependencies/placholder_overlay_deps.swift`
Rename `-enable-cas` to `-compile-cache-job` to align with clang option
names and promote that to a new driver only flag.
Few other additions to driver flag for caching behaviors:
* `-compile-cache-remarks`: now cache hit/miss remarks are guarded behind
this flag
* `-compile-cache-skip`: skip replaying from the cache. Useful as a
debugging tool to do the compilation using CAS inputs even the output
is a hit from the cache.
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.
