fix discard_graph_edges_test to properly depend on $(JAVABASE)

- no longer uses $bazel_javabase from testenv.sh
- works with absolute $(JAVABASE) paths and JDK's other than loc

Progress towards #8033

Closes #8037.

PiperOrigin-RevId: 243797243

src/test/shell/integration/BUILD

diff --git a/src/test/shell/integration/BUILD b/src/test/shell/integration/BUILD
index 7cce059..59d10b7 100644
--- a/src/test/shell/integration/BUILD
+++ b/src/test/shell/integration/BUILD
@@ -401,12 +401,15 @@
     name = "discard_graph_edges_test",
     size = "medium",
     srcs = ["discard_graph_edges_test.sh"],
+    args = ["$(JAVABASE)"],
     data = [
         ":discard_graph_edges_lib.sh",
         ":test-deps",
+        "@bazel_tools//tools/bash/runfiles",
     ],
     shard_count = 6,
     tags = ["no_windows"],
+    toolchains = ["@bazel_tools//tools/jdk:current_java_runtime"],
 )
 
 sh_test(

src/test/shell/integration/discard_graph_edges_lib.sh

diff --git a/src/test/shell/integration/discard_graph_edges_lib.sh b/src/test/shell/integration/discard_graph_edges_lib.sh
index d603886..b7675ac 100644
--- a/src/test/shell/integration/discard_graph_edges_lib.sh
+++ b/src/test/shell/integration/discard_graph_edges_lib.sh
@@ -24,7 +24,6 @@
   local item="$2"
   # We can't use + here because Macs don't recognize it as a special character
   # by default.
-  grep "$item" "$histofile" \
-      | sed -e 's/^ *[0-9][0-9]*: *\([0-9][0-9]*\) .*$/\1/' \
-      || fail "Couldn't get item from $histofile"
+  (grep "$item" "$histofile" || echo "") \
+      | sed -e 's/^ *[0-9][0-9]*: *\([0-9][0-9]*\) .*$/\1/'
 }

src/test/shell/integration/discard_graph_edges_test.sh

diff --git a/src/test/shell/integration/discard_graph_edges_test.sh b/src/test/shell/integration/discard_graph_edges_test.sh
index 2ec2826..c8d62b1 100755
--- a/src/test/shell/integration/discard_graph_edges_test.sh
+++ b/src/test/shell/integration/discard_graph_edges_test.sh
@@ -16,12 +16,51 @@
 #
 # discard_graph_edges_test.sh: basic tests for the --discard_graph_edges flag.
 
-# Load the test setup defined in the parent directory
-CURRENT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-source "${CURRENT_DIR}/../integration_test_setup.sh" \
+# --- begin runfiles.bash initialization ---
+# Copy-pasted from Bazel's Bash runfiles library (tools/bash/runfiles/runfiles.bash).
+set -euo pipefail
+if [[ ! -d "${RUNFILES_DIR:-/dev/null}" && ! -f "${RUNFILES_MANIFEST_FILE:-/dev/null}" ]]; then
+  if [[ -f "$0.runfiles_manifest" ]]; then
+    export RUNFILES_MANIFEST_FILE="$0.runfiles_manifest"
+  elif [[ -f "$0.runfiles/MANIFEST" ]]; then
+    export RUNFILES_MANIFEST_FILE="$0.runfiles/MANIFEST"
+  elif [[ -f "$0.runfiles/bazel_tools/tools/bash/runfiles/runfiles.bash" ]]; then
+    export RUNFILES_DIR="$0.runfiles"
+  fi
+fi
+if [[ -f "${RUNFILES_DIR:-/dev/null}/bazel_tools/tools/bash/runfiles/runfiles.bash" ]]; then
+  source "${RUNFILES_DIR}/bazel_tools/tools/bash/runfiles/runfiles.bash"
+elif [[ -f "${RUNFILES_MANIFEST_FILE:-/dev/null}" ]]; then
+  source "$(grep -m1 "^bazel_tools/tools/bash/runfiles/runfiles.bash " \
+            "$RUNFILES_MANIFEST_FILE" | cut -d ' ' -f 2-)"
+else
+  echo >&2 "ERROR: cannot find @bazel_tools//tools/bash/runfiles:runfiles.bash"
+  exit 1
+fi
+# --- end runfiles.bash initialization ---
+
+source "$(rlocation "io_bazel/src/test/shell/integration_test_setup.sh")" \
   || { echo "integration_test_setup.sh not found!" >&2; exit 1; }
-source "${CURRENT_DIR}/discard_graph_edges_lib.sh" \
-  || { echo "${CURRENT_DIR}/discard_graph_edges_lib.sh not found!" >&2; exit 1; }
+source "$(rlocation "io_bazel/src/test/shell/integration/discard_graph_edges_lib.sh")" \
+  || { echo "discard_graph_edges_lib.sh not found!" >&2; exit 1; }
+
+IS_WINDOWS=false
+case "$(uname | tr [:upper:] [:lower:])" in
+msys*|mingw*|cygwin*)
+  IS_WINDOWS=true
+esac
+
+if "$IS_WINDOWS"; then
+  EXE_EXT=".exe"
+else
+  EXE_EXT=""
+fi
+
+javabase="$1"
+if [[ $javabase = external/* ]]; then
+  javabase=${javabase#external/}
+fi
+jmaptool="$(rlocation "${javabase}/bin/jmap${EXE_EXT}")"
 
 #### SETUP #############################################################
 
@@ -167,7 +206,7 @@
         local = 1,
         tools = [':cclib'],
         cmd = 'server_pid=\$\$(cat $server_pid_fifo) ; ' +
-              '${bazel_javabase}/bin/jmap -histo:live \$\$server_pid > ' +
+              '${jmaptool} -histo:live \$\$server_pid > ' +
               '\$(location histo.txt) ' +
               '|| echo "server_pid in genrule: \$\$server_pid"'
        )
@@ -365,7 +404,7 @@
 
   bazel build $BUILD_FLAGS //foo:foo \
       >& "$TEST_log" || fail "Expected success"
-  "${bazel_javabase}/bin/jmap" -histo:live "$(bazel info server_pid)" > histo.txt
+  "$jmaptool" -histo:live "$(bazel info server_pid)" > histo.txt
   genrule_action_count="$(extract_histogram_count histo.txt \
         'GenRuleAction$')"
   if [[ "$genrule_action_count" -lt 1 ]]; then