Don't crash on `module-info.java`s is we can't load `java.base`

This can happen when compiling a module declaration against a non-modular
bootclasspath. The lookup of `java.base` is only used to get its version, which
we can skip.

PiperOrigin-RevId: 421040147

2 files changed, 111 insertions, 5 deletions

diff --git a/java/com/google/turbine/binder/ModuleBinder.java b/java/com/google/turbine/binder/ModuleBinder.java
index 0b0180e..e88440d 100644
--- a/java/com/google/turbine/binder/ModuleBinder.java
+++ b/java/com/google/turbine/binder/ModuleBinder.java
@@ -137,15 +137,16 @@ public class ModuleBinder {
       }
     }
     if (!requiresJavaBase) {
-      // everything requires java.base, either explicitly or implicitly
-      ModuleInfo javaBaseModule = moduleEnv.getNonNull(ModuleSymbol.JAVA_BASE);
+      // Everything requires java.base, either explicitly or implicitly.
+      ModuleInfo javaBaseModule = moduleEnv.get(ModuleSymbol.JAVA_BASE);
+      // Tolerate a missing java.base module, e.g. when compiling a module against a non-modular
+      // bootclasspath, and just omit the version below.
+      String javaBaseVersion = javaBaseModule != null ? javaBaseModule.version() : null;
       requires =
           ImmutableList.<RequireInfo>builder()
               .add(
                   new RequireInfo(
-                      ModuleSymbol.JAVA_BASE.name(),
-                      TurbineFlag.ACC_MANDATED,
-                      javaBaseModule.version()))
+                      ModuleSymbol.JAVA_BASE.name(), TurbineFlag.ACC_MANDATED, javaBaseVersion))
               .addAll(requires.build());
     }
 
diff --git a/javatests/com/google/turbine/lower/MissingJavaBaseModule.java b/javatests/com/google/turbine/lower/MissingJavaBaseModule.java
new file mode 100644
index 0000000..230b18f
--- /dev/null
+++ b/javatests/com/google/turbine/lower/MissingJavaBaseModule.java
@@ -0,0 +1,105 @@
+/*
+ * Copyright 2021 Google Inc. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.turbine.lower;
+
+import static com.google.common.base.StandardSystemProperty.JAVA_CLASS_VERSION;
+import static com.google.common.collect.ImmutableMap.toImmutableMap;
+import static org.junit.Assert.assertEquals;
+
+import com.google.common.base.Supplier;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.turbine.binder.ClassPath;
+import com.google.turbine.binder.CtSymClassBinder;
+import com.google.turbine.binder.JimageClassBinder;
+import com.google.turbine.binder.bound.ModuleInfo;
+import com.google.turbine.binder.bytecode.BytecodeBoundClass;
+import com.google.turbine.binder.env.Env;
+import com.google.turbine.binder.lookup.TopLevelIndex;
+import com.google.turbine.binder.sym.ClassSymbol;
+import com.google.turbine.binder.sym.ModuleSymbol;
+import java.util.Map;
+import java.util.Optional;
+import org.jspecify.nullness.Nullable;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class MissingJavaBaseModule {
+
+  @Test
+  public void test() throws Exception {
+
+    Map<String, String> sources = ImmutableMap.of("module-info.java", "module foo {}");
+
+    Map<String, byte[]> expected =
+        IntegrationTestSupport.runJavac(
+            sources, ImmutableList.of(), ImmutableList.of("--release", "9", "--module-version=42"));
+
+    ClassPath base =
+        Double.parseDouble(JAVA_CLASS_VERSION.value()) < 54
+            ? JimageClassBinder.bindDefault()
+            : CtSymClassBinder.bind(9);
+    ClassPath bootclasspath =
+        new ClassPath() {
+          @Override
+          public Env<ClassSymbol, BytecodeBoundClass> env() {
+            return base.env();
+          }
+
+          @Override
+          public Env<ModuleSymbol, ModuleInfo> moduleEnv() {
+            return new Env<ModuleSymbol, ModuleInfo>() {
+              @Override
+              public @Nullable ModuleInfo get(ModuleSymbol sym) {
+                if (sym.name().equals("java.base")) {
+                  return null;
+                }
+                return base.moduleEnv().get(sym);
+              }
+            };
+          }
+
+          @Override
+          public TopLevelIndex index() {
+            return base.index();
+          }
+
+          @Override
+          public @Nullable Supplier<byte[]> resource(String path) {
+            return base.resource(path);
+          }
+        };
+    Map<String, byte[]> actual =
+        IntegrationTestSupport.runTurbine(
+            sources,
+            ImmutableList.of(),
+            bootclasspath,
+            Optional.of("42"),
+            /* javacopts= */ ImmutableList.of());
+
+    assertEquals(dump(expected), dump(actual));
+  }
+
+  private String dump(Map<String, byte[]> map) throws Exception {
+    return IntegrationTestSupport.dump(
+        map.entrySet().stream()
+            .filter(e -> e.getKey().endsWith("module-info"))
+            .collect(toImmutableMap(Map.Entry::getKey, Map.Entry::getValue)));
+  }
+}