Rework the backing machinery for System.getProperty to utilize our ow…

…n registry

The existing system is brittle properties are read as global symbols when
uncompiled, but as `goog.define` flags when compiled. This is error-prone and
there's no clear linkage between the two.

To replace it, system properties now need to be explicitly registered. For now
we'll only be supporting registering properties that come from a `goog.define`
flag.

For backwards compatibility we'll fallback to `goog.getObjectByName` if a
property is not registered, but we will make this an error in the future.

PiperOrigin-RevId: 689188398

docs/best-practices.md

@@ -210,8 +210,23 @@ production JavaScript code.
 ### Custom Compile-Time Code Stripping
 
 You can implement your own configuration based stripping with
-`System.getProperty()`. In the following example, the compiler will statically
-evaluate the condition and remove the entire if/else control statement.
+`System.getProperty()` paired with a `goog.define` property in JS. In the
+following example, the compiler will statically evaluate the condition and
+remove the entire if/else control statement.
+
+```js
+const jre = goog.require('jre');
+
+// First declare the goog.define name. If you don't use a string type, it will
+// be stringified when read in Java.
+/** @define {string} */
+const whatever = goog.define('some.define', 'NO');
+
+// Add the define to the set of system properties. The name must match the
+// goog.define name, and the value must be the result of the corresponding
+// goog.define call.
+jre.addSystemPropertyFromGoogDefine('some.define', whatever);
+```
 
 ```java
 if (System.getProperty("some.define") == "YES") {
@@ -221,7 +236,7 @@ if (System.getProperty("some.define") == "YES") {
 }
 ```
 
-```python
+```build
 js_binary(
     name = "optimized_j2cl_app",
     defs = ["--define=some.define=YES"] + J2CL_OPTIMIZED_DEFS,

jre/java/java/lang/jre.js

@@ -20,37 +20,104 @@
 
 goog.provide('jre');
 
+/** @private @const {!Object<string, ?string>} */
+jre.systemProperties_ = Object.create(null);
+
+/**
+ * Adds a system property connected to goog.define.
+ * Properties being registered must have a name that matches the goog.define
+ * name and the value must be the result of the goog.define call. These values
+ * will then be accessible via System.getProperty in Java.
+ * @param {string} googDefineName
+ * @param {?string} googDefineValue
+ */
+jre.addSystemPropertyFromGoogDefine = function(
+    googDefineName, googDefineValue) {
+  // Values from goog.define are well-known to the compiler and will be
+  // statically substituted. Therefore this method can be a no-op when compiled.
+  if (!COMPILED) {
+    if (googDefineName in jre.systemProperties_) {
+      throw new Error(
+          `Attempting to redeclare system property '${googDefineName}'.`);
+    }
+    jre.systemProperties_[googDefineName] = googDefineValue;
+  }
+};
+
+/**
+ * Returns the value of a system property.
+ * @param {string} name
+ * @param {?string=} defaultValue
+ * @return {?string}
+ */
+jre.getSystemProperty = function(name, defaultValue = null) {
+  // For backwards compatibility, fallback to goog.getObjectByName if it's not
+  // in the registry.
+  const rv = jre.systemProperties_[name] ?? goog.getObjectByName(name);
+  return rv == null ? defaultValue : String(rv);
+};
+
+// Add core defines
+jre.addSystemPropertyFromGoogDefine('COMPILED', String(COMPILED));
+jre.addSystemPropertyFromGoogDefine('goog.DEBUG', String(goog.DEBUG));
+jre.addSystemPropertyFromGoogDefine('goog.LOCALE', goog.LOCALE);
+jre.addSystemPropertyFromGoogDefine(
+    'goog.TRUSTED_SITE', String(goog.TRUSTED_SITE));
+jre.addSystemPropertyFromGoogDefine(
+    'goog.FEATURESET_YEAR', String(goog.FEATURESET_YEAR));
+
 /** @define {string} */
 jre.classMetadata = goog.define('jre.classMetadata', 'SIMPLE');
+jre.addSystemPropertyFromGoogDefine('jre.classMetadata', jre.classMetadata);
+
 /** @define {string} */
 jre.checkedMode =
     goog.define('jre.checkedMode', goog.DEBUG ? 'ENABLED' : 'DISABLED');
+jre.addSystemPropertyFromGoogDefine('jre.checkedMode', jre.checkedMode);
 
 
 goog.provide('jre.checks');
 
 /** @define {string} */
 jre.checks.checkLevel = goog.define('jre.checks.checkLevel', 'NORMAL');
+jre.addSystemPropertyFromGoogDefine(
+    'jre.checks.checkLevel', jre.checks.checkLevel);
+
 /** @define {string} */
 jre.checks.bounds = goog.define('jre.checks.bounds', 'AUTO');
+jre.addSystemPropertyFromGoogDefine('jre.checks.bounds', jre.checks.bounds);
+
+
 /** @define {string} */
 jre.checks.api = goog.define('jre.checks.api', 'AUTO');
+jre.addSystemPropertyFromGoogDefine('jre.checks.api', jre.checks.api);
+
 /** @define {string} */
 jre.checks.numeric = goog.define('jre.checks.numeric', 'AUTO');
+jre.addSystemPropertyFromGoogDefine('jre.checks.numeric', jre.checks.numeric);
+
 /** @define {string} */
 jre.checks.type = goog.define('jre.checks.type', 'AUTO');
+jre.addSystemPropertyFromGoogDefine('jre.checks.type', jre.checks.type);
+
 /** @define {string} */
 jre.checks.critical = goog.define('jre.checks.critical', 'AUTO');
+jre.addSystemPropertyFromGoogDefine('jre.checks.critical', jre.checks.critical);
 
 
 goog.provide('jre.logging');
 
 /** @define {string} */
 jre.logging.logLevel =
     goog.define('jre.logging.logLevel', goog.DEBUG ? 'ALL' : 'SEVERE');
+jre.addSystemPropertyFromGoogDefine(
+    'jre.logging.logLevel', jre.logging.logLevel);
+
 /** @define {string} */
 jre.logging.simpleConsoleHandler =
     goog.define('jre.logging.simpleConsoleHandler', 'ENABLED');
+jre.addSystemPropertyFromGoogDefine(
+    'jre.logging.simpleConsoleHandler', jre.logging.simpleConsoleHandler);
 
 // Provide a stub for field preserver to make things work without full
 // compilation.

jre/java/javaemul/internal/nativebootstrap/Util.impl.java.js

@@ -30,17 +30,14 @@ class Util {
    * if it is not defined.
    *
    * @param {string} name
-   * @param {?string=} opt_defaultValue
+   * @param {?string=} defaultValue
    * @return {?string}
    * @public
+   * @noinline
    */
-  static $getDefine(name, opt_defaultValue) {
-    // Default the optional param. Note that we are not using the common
-    // 'opt_value || default_value' pattern otherwise that would replace
-    // empty string with null value.
-    var defaultValue = opt_defaultValue == null ? null : opt_defaultValue;
-    var rv = goog.getObjectByName(name);
-    return rv == null ? defaultValue : String(rv);
+  // TODO(b/374872678): Remove the indirection through $getDefine.
+  static $getDefine(name, defaultValue = null) {
+    return jre.getSystemProperty(name, defaultValue);
   }
 
   /**

junit/generator/javatests/com/google/j2cl/junit/integration/stacktrace/data/KotlinThrowsInJsFunction.stacktrace_j2cl.txt

@@ -1,6 +1,6 @@
 java.lang.RuntimeException: __the_message__!
     at com.google.j2cl.junit.integration.stacktrace.data.KotlinThrowsInJsFunction$MyFunctionImpl.run(KotlinThrowsInJsFunction.kt:50)
-    at lambda(jre/java/jre.js/javaemul/internal/nativebootstrap/Util.impl.java.js:199:31)
+    at lambda(jre/java/jre.js/javaemul/internal/nativebootstrap/Util.impl.java.js:196:31)
     at com.google.j2cl.junit.integration.stacktrace.data.KotlinThrowsInJsFunction.executesFunction(KotlinThrowsInJsFunction.kt:55)
     at com.google.j2cl.junit.integration.stacktrace.data.KotlinThrowsInJsFunction$1.run(KotlinThrowsInJsFunction.kt:41)
     at com.google.j2cl.junit.integration.stacktrace.data.KotlinThrowsInJsFunction.executesFunction(KotlinThrowsInJsFunction.kt:55)

junit/generator/javatests/com/google/j2cl/junit/integration/stacktrace/data/KotlinThrowsInJsFunction.stacktrace_j2cl_compiled.txt

@@ -1,6 +1,6 @@
 java.lang.RuntimeException: __the_message__!
     at com.google.j2cl.junit.integration.stacktrace.data.KotlinThrowsInJsFunction$MyFunctionImpl.run(KotlinThrowsInJsFunction.kt:50)
-    at apply(<blaze-out>/jre/java/jre.js/javaemul/internal/nativebootstrap/Util.impl.java.js:199:31)
+    at apply(<blaze-out>/jre/java/jre.js/javaemul/internal/nativebootstrap/Util.impl.java.js:196:31)
     at com.google.j2cl.junit.integration.stacktrace.data.KotlinThrowsInJsFunction.executesFunction(KotlinThrowsInJsFunction.kt:55)
     at com.google.j2cl.junit.integration.stacktrace.data.KotlinThrowsInJsFunction$1.run(KotlinThrowsInJsFunction.kt:41)
     at com.google.j2cl.junit.integration.stacktrace.data.KotlinThrowsInJsFunction.executesFunction(KotlinThrowsInJsFunction.kt:55)

junit/generator/javatests/com/google/j2cl/junit/integration/stacktrace/data/ThrowsInJsFunction.stacktrace_j2cl.txt

@@ -1,6 +1,6 @@
 java.lang.RuntimeException: __the_message__!
     at com.google.j2cl.junit.integration.stacktrace.data.ThrowsInJsFunction$MyFunctionImpl.run(ThrowsInJsFunction.java:55)
-    at lambda(jre/java/jre.js/javaemul/internal/nativebootstrap/Util.impl.java.js:199:31)
+    at lambda(jre/java/jre.js/javaemul/internal/nativebootstrap/Util.impl.java.js:196:31)
     at com.google.j2cl.junit.integration.stacktrace.data.ThrowsInJsFunction.executesFunction(ThrowsInJsFunction.java:60)
     at com.google.j2cl.junit.integration.stacktrace.data.ThrowsInJsFunction$1.run(ThrowsInJsFunction.java:46)
     at com.google.j2cl.junit.integration.stacktrace.data.ThrowsInJsFunction.executesFunction(ThrowsInJsFunction.java:60)

junit/generator/javatests/com/google/j2cl/junit/integration/stacktrace/data/ThrowsInJsFunction.stacktrace_j2cl_compiled.txt

@@ -1,6 +1,6 @@
 java.lang.RuntimeException: __the_message__!
     at com.google.j2cl.junit.integration.stacktrace.data.ThrowsInJsFunction$MyFunctionImpl.run(ThrowsInJsFunction.java:55)
-    at apply(<blaze-out>/jre/java/jre.js/javaemul/internal/nativebootstrap/Util.impl.java.js:199:31)
+    at apply(<blaze-out>/jre/java/jre.js/javaemul/internal/nativebootstrap/Util.impl.java.js:196:31)
     at com.google.j2cl.junit.integration.stacktrace.data.ThrowsInJsFunction.executesFunction(ThrowsInJsFunction.java:60)
     at com.google.j2cl.junit.integration.stacktrace.data.ThrowsInJsFunction$1.run(ThrowsInJsFunction.java:46)
     at com.google.j2cl.junit.integration.stacktrace.data.ThrowsInJsFunction.executesFunction(ThrowsInJsFunction.java:60)