Make repository_chache non-experimental and enable by default

Make the --experimental_repository_cache option no longer experimental and enable
the cache by default. The default location is in the a separate directory under the
install base (under .cache/bazel user's home directory); this means it is shared
between workspaces und not between different versions of bazel. We plan to also
share it between different bazel versions in the future.

Fixes bazelbuild#4676.

RELNOTES:
  repository_cache is no longer experimental and enabled by default.

Change-Id: I8499c2d1811e0fe8d830796e07cd6f8bc75e48ba
PiperOrigin-RevId: 187172766

src/main/java/com/google/devtools/build/lib/bazel/BazelRepositoryModule.java

@@ -51,6 +51,7 @@
 import com.google.devtools.build.lib.bazel.rules.workspace.NewGitRepositoryRule;
 import com.google.devtools.build.lib.bazel.rules.workspace.NewHttpArchiveRule;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
+import com.google.devtools.build.lib.events.Event;
 import com.google.devtools.build.lib.pkgcache.PackageCacheOptions;
 import com.google.devtools.build.lib.rules.repository.LocalRepositoryFunction;
 import com.google.devtools.build.lib.rules.repository.LocalRepositoryRule;
@@ -73,12 +74,14 @@
 import com.google.devtools.build.lib.skyframe.SkyValueDirtinessChecker;
 import com.google.devtools.build.lib.util.io.TimestampGranularityMonitor;
 import com.google.devtools.build.lib.vfs.FileSystem;
+import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.devtools.build.skyframe.SkyKey;
 import com.google.devtools.build.skyframe.SkyValue;
 import com.google.devtools.common.options.OptionsBase;
 import com.google.devtools.common.options.OptionsProvider;
+import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -91,6 +94,9 @@
  */
 public class BazelRepositoryModule extends BlazeModule {
 
+  // Default location (relative to output user root) of the repository cache.
+  public static final String DEFAULT_CACHE_LOCATION = "cache/repos/v1";
+
   // A map of repository handlers that can be looked up by rule class name.
   private final ImmutableMap<String, RepositoryFunction> repositoryHandlers;
   private final AtomicBoolean isFetch = new AtomicBoolean(false);
@@ -210,7 +216,23 @@ public void beforeCommand(CommandEnvironment env) {
         }
         repositoryCache.setRepositoryCachePath(repositoryCachePath);
       } else {
-        repositoryCache.setRepositoryCachePath(null);
+        Path repositoryCachePath =
+            env.getDirectories()
+                .getServerDirectories()
+                .getOutputUserRoot()
+                .getRelative(DEFAULT_CACHE_LOCATION);
+        try {
+          FileSystemUtils.createDirectoryAndParents(repositoryCachePath);
+          repositoryCache.setRepositoryCachePath(repositoryCachePath);
+        } catch (IOException e) {
+          env.getReporter()
+              .handle(
+                  Event.warn(
+                      "Failed to set up cache at "
+                          + repositoryCachePath.toString()
+                          + ": "
+                          + e.getMessage()));
+        }
       }
 
       if (repoOptions.experimentalDistdir != null) {

src/main/java/com/google/devtools/build/lib/bazel/repository/RepositoryOptions.java

@@ -34,7 +34,8 @@
 public class RepositoryOptions extends OptionsBase {
 
   @Option(
-    name = "experimental_repository_cache",
+    name = "repository_cache",
+    oldName = "experimental_repository_cache",
     defaultValue = "null",
     documentationCategory = OptionDocumentationCategory.BAZEL_CLIENT_OPTIONS,
     effectTags = {OptionEffectTag.BAZEL_INTERNAL_CONFIGURATION},

src/test/shell/bazel/external_integration_test.sh

@@ -1105,7 +1105,7 @@ EOF
 }
 
 function test_repository_cache_relative_path() {
-  # Verify that --experimental_repository_cache works for query and caches soly
+  # Verify that --repository_cache works for query and caches soly
   # based on the predicted hash, for a repository-cache location given as path
   # relative to the WORKSPACE
   WRKDIR=$(mktemp -d "${TEST_TMPDIR}/testXXXXXX")
@@ -1144,7 +1144,7 @@ http_archive(
 )
 EOF
   # Use the external repository once to make sure it is cached.
-  bazel build --experimental_repository_cache="../cache" '@ext//:bar' \
+  bazel build --repository_cache="../cache" '@ext//:bar' \
       || fail "expected sucess"
 
   # Now "go offline" and clean local resources.
@@ -1154,7 +1154,7 @@ EOF
 
   # The value should still be available from the repository cache
   bazel query 'deps("@ext//:bar")' \
-        --experimental_repository_cache="../cache" > "${TEST_log}" \
+        --repository_cache="../cache" > "${TEST_log}" \
       || fail "Expected success"
   expect_log '@ext//:foo'
 
@@ -1172,11 +1172,76 @@ http_archive(
 )
 EOF
   bazel query 'deps("@ext//:bar")' \
-        --experimental_repository_cache="../cache" > "${TEST_log}" \
+        --repository_cache="../cache" > "${TEST_log}" \
       || fail "Expected success"
   expect_log '@ext//:foo'
 }
 
+test_default_cache()
+{
+  # Verify that the default cache works for query and caches soly
+  # based on the predicted hash, for a repository-cache location given as path
+  # relative to the WORKSPACE
+  WRKDIR=$(mktemp -d "${TEST_TMPDIR}/testXXXXXX")
+  cd "${WRKDIR}"
+  mkdir ext
+  cat > ext/BUILD <<'EOF'
+genrule(
+  name="foo",
+  outs=["foo.txt"],
+  cmd="echo Hello World > $@",
+)
+genrule(
+  name="bar",
+  outs=["bar.txt"],
+  srcs=[":foo"],
+  cmd="cp $< $@",
+)
+EOF
+  zip ext.zip ext/*
+  rm -rf ext
+  sha256=$(sha256sum ext.zip | head -c 64)
+
+  rm -rf main
+  mkdir main
+  cd main
+  cat > WORKSPACE <<EOF
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+http_archive(
+  name="ext",
+  strip_prefix="ext",
+  urls=["file://${WRKDIR}/ext.zip"],
+  sha256="${sha256}",
+)
+EOF
+  # Use the external repository once to make sure it is cached.
+  bazel build '@ext//:bar' || fail "expected sucess"
+
+  # Now "go offline" and clean local resources.
+  rm -f "${WRKDIR}/ext.zip"
+  bazel clean --expunge
+
+  # The value should still be available from the repository cache
+  bazel query 'deps("@ext//:bar")' > "${TEST_log}" || fail "Expected success"
+  expect_log '@ext//:foo'
+
+  # Clean again.
+  bazel clean --expunge
+  # Even with a different source URL, the cache sould be consulted.
+
+  cat > WORKSPACE <<EOF
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+http_archive(
+  name="ext",
+  strip_prefix="ext",
+  urls=["http://doesnotexist.example.com/invalidpath/othername.zip"],
+  sha256="${sha256}",
+)
+EOF
+  bazel query 'deps("@ext//:bar")' > "${TEST_log}" || fail "Expected success"
+  expect_log '@ext//:foo'
+}
+
 function test_repository_cache() {
   # Verify that --experimental_repository_cache works for query and caches soly
   # based on the predicted hash.