[clang][cas] Remove CASOptions from module context hash

We want to avoid spurious cache misses due to module context hash
including the -fcas-path, -fcas-plugin-path, -fcas-plugin-option
options. These cannot cause collisions since we only have a single CAS
for the dependency scanner, and they cannot collide with non-cas
invocations, because the include-tree and cas-fs-working-dir options are
still present.

rdar://108341513
(cherry picked from commit 64bbbc0)

Author: benlangmuir

clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp

@@ -297,6 +297,8 @@ static std::string getModuleContextHash(const ModuleDeps &MD,
       MutableCI.getFileSystemOpts().CASFileSystemRootID, "");
   llvm::SaveAndRestore<std::vector<std::string>> RestorePrefixMappings(
       MutableCI.getFrontendOpts().PathPrefixMappings, {});
+  llvm::SaveAndRestore<CASOptions> RestoreCASOptions(
+      MutableCI.getCASOpts(), {});
 
   // Hash the BuildInvocation without any input files.
   SmallVector<const char *, 32> Args;

clang/test/ClangScanDeps/modules-cas-context-hash.c

@@ -0,0 +1,83 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: sed "s|DIR|%/t|g" %t/cdb1.json.template > %t/cdb1.json
+// RUN: sed "s|DIR|%/t|g" %t/cdb2.json.template > %t/cdb2.json
+
+// RUN: clang-scan-deps -compilation-database %t/cdb1.json -module-files-dir %t/outputs \
+// RUN:   -cas-path %t/cas1 -format experimental-include-tree-full \
+// RUN:   > %t/result.json
+// RUN: echo "=====" >> %t/result.json
+// RUN: clang-scan-deps -compilation-database %t/cdb2.json -module-files-dir %t/outputs \
+// RUN:   -cas-path %t/cas2 -format experimental-include-tree-full \
+// RUN:   >> %t/result.json
+
+// RUN: cat %t/result.json | FileCheck %s -DPREFIX=%/t
+
+// CHECK: "modules": [
+// CHECK:   {
+// CHECK:     "cache-key": "llvmcas://[[KEY:[[:xdigit:]]+]]"
+// CHECK:     "context-hash": "[[HASH:[A-Z0-9]+]]",
+// CHECK:     "name": "Mod"
+// CHECK:   }
+// CHECK: ]
+// CHECK: "translation-units": [
+// CHECK:   {
+// CHECK:     "commands": [
+// CHECK:       {
+// CHECK:         "clang-module-deps": [
+// CHECK:           {
+// CHECK:             "context-hash": "[[HASH]]"
+// CHECK:             "module-name": "Mod"
+// CHECK:           }
+// CHECK:         ],
+// CHECK:         "command-line": [
+// CHECK:           "-fmodule-file-cache-key"
+// CHECK:           "[[PREFIX]]/outputs/[[HASH]]/Mod-[[HASH]].pcm"
+// CHECK:           "llvmcas://[[KEY]]"
+// CHECK:         ]
+
+// CHECK-LABEL: =====
+
+// CHECK: "modules": [
+// CHECK:   {
+// CHECK:     "cache-key": "llvmcas://[[KEY]]"
+// CHECK:     "context-hash": "[[HASH]]"
+// CHECK:     "name": "Mod"
+// CHECK:   }
+// CHECK: "translation-units": [
+// CHECK:   {
+// CHECK:     "commands": [
+// CHECK:       {
+// CHECK:         "clang-module-deps": [
+// CHECK:           {
+// CHECK:             "context-hash": "[[HASH]]"
+// CHECK:             "module-name": "Mod"
+// CHECK:           }
+// CHECK:         ],
+// CHECK:         "command-line": [
+// CHECK:           "-fmodule-file-cache-key"
+// CHECK:           "[[PREFIX]]/outputs/[[HASH]]/Mod-[[HASH]].pcm"
+// CHECK:           "llvmcas://[[KEY]]"
+// CHECK:         ]
+
+//--- cdb1.json.template
+[{
+  "directory": "DIR",
+  "command": "clang -Xclang -fcas-plugin-path -Xclang /1 -Xclang -fcas-plugin-option -Xclang a=x -fsyntax-only DIR/tu.c -fmodules -fimplicit-module-maps -fmodules-cache-path=DIR/cache1",
+  "file": "DIR/tu.c"
+}]
+
+//--- cdb2.json.template
+[{
+  "directory": "DIR",
+  "command": "clang -Xclang -fcas-plugin-path -Xclang /2 -Xclang -fcas-plugin-option -Xclang b=y -fsyntax-only DIR/tu.c -fmodules -fimplicit-module-maps -fmodules-cache-path=DIR/cache2",
+  "file": "DIR/tu.c"
+}]
+
+//--- module.modulemap
+module Mod { header "Mod.h" }
+
+//--- Mod.h
+
+//--- tu.c
+#include "Mod.h"