Report declareIcuTemplate() placeholders in non-canonical format

Placeholders are always formated in UPPER_SNAKE_CASE in XMB / XTB files
and in ICU template messages. Explicitly report an error if a
`declareIcuTemplate()` attempts to use a placeholder name in some other
format for its `example` or `original_code` maps.

NOTE: This change does not report errors for code that was accepted before.

It was already the case that you would get an error message if you tried
to refer to `lowerCamelCasePlaceholderName` in the `example` or
`original_code` part of a `declareIcuTemplate()` message, but the error
was confusing. It would say that the placeholder didn't exist,
even if you actually wrote "{lowerCamelCasePlaceholderName}" in the
template string.

This change also adds a `JsMessage` method for getting a list of the
placeholder names in canonical format.

PiperOrigin-RevId: 700030842

Author: brad4d

src/com/google/javascript/jscomp/JsMessage.java

@@ -105,9 +105,21 @@ public PlaceholderFormatException(String msg) {
 
   public abstract ImmutableMap<String, String> getPlaceholderNameToOriginalCodeMap();
 
-  /** Gets a set of the registered placeholders in this message. */
+  /**
+   * Gets a set of the registered placeholders in this message in lowerCamelCase format.
+   *
+   * <p>This is the format used in `goog.getMsg()` declarations.
+   */
   public abstract ImmutableSet<String> jsPlaceholderNames();
 
+  /**
+   * Gets a set of the registered placeholders in this message in UPPER_SNAKE_CASE format.
+   *
+   * <p>This is the format stored into XMB / XTB files and used in `declareIcuTemplate()
+   * declarations.
+   */
+  public abstract ImmutableSet<String> canonicalPlaceholderNames();
+
   public String getPlaceholderOriginalCode(PlaceholderReference placeholderReference) {
     return getPlaceholderNameToOriginalCodeMap()
         .getOrDefault(placeholderReference.getStoredPlaceholderName(), "-");
@@ -372,8 +384,12 @@ public static final class Builder {
     private @Nullable String alternateId;
 
     private final List<Part> parts = new ArrayList<>();
-    // Placeholder names in JS code format
+    // Placeholder names in JS code format (lowerCamelCase),
+    // which is used for `goog.getMsg()` messages
     private final Set<String> jsPlaceholderNames = new LinkedHashSet<>();
+    // Placeholder names in canonical format (UPPER_SNAKE_CASE)
+    // which is used in XMB / XTB files and `declareIcuTemplate()` messages.
+    private final Set<String> canonicalPlaceholderNames = new LinkedHashSet<>();
     private ImmutableMap<String, String> placeholderNameToExampleMap = ImmutableMap.of();
     private ImmutableMap<String, String> placeholderNameToOriginalCodeMap = ImmutableMap.of();
 
@@ -409,6 +425,7 @@ public Builder appendPart(Part part) {
       parts.add(part);
       if (part.isPlaceholder()) {
         jsPlaceholderNames.add(part.getJsPlaceholderName());
+        canonicalPlaceholderNames.add(part.getCanonicalPlaceholderName());
       }
       return this;
     }
@@ -542,7 +559,8 @@ public JsMessage build() {
           meaning,
           placeholderNameToExampleMap,
           placeholderNameToOriginalCodeMap,
-          ImmutableSet.copyOf(jsPlaceholderNames));
+          ImmutableSet.copyOf(jsPlaceholderNames),
+          ImmutableSet.copyOf(canonicalPlaceholderNames));
     }
   }
 

src/com/google/javascript/jscomp/JsMessageVisitor.java

@@ -1051,6 +1051,7 @@ private IcuMessageTemplateString extractIcuMessageTemplateString(Node stringExpr
   private interface JsMessageOptions {
     // Replace `'<'` with `'&lt;'` in the message.
     boolean isEscapeLessThan();
+
     // Replace these escaped entities with their literal characters in the message
     // (Overrides escapeLessThan)
     // '&lt;' -> '<'
@@ -1216,6 +1217,14 @@ private IcuTemplateOptions extractIcuTemplateOptions(Node optionsBag) throws Mal
             .addAll(placeholderOriginalCodeMap.keySet())
             .build();
 
+    for (String placeholderName : placeholderNames) {
+      if (!JsMessage.isCanonicalPlaceholderNameFormat(placeholderName)) {
+        throw new MalformedException(
+            SimpleFormat.format("Placeholder not in UPPER_SNAKE_CASE: %s", placeholderName),
+            optionsBag);
+      }
+    }
+
     // NOTE: The getX() methods below should all do little to no computation.
     // In particular, all checking for MalformedExceptions must be done before creating this object.
     return new IcuTemplateOptions() {

test/com/google/javascript/jscomp/JsMessageVisitorTest.java

@@ -212,6 +212,65 @@ public void testIcuTemplatePlaceholderTypo() {
     assertThat(messages).isEmpty();
   }
 
+  @Test
+  public void testIcuTemplatePlaceholderUpperSnakeCase() {
+    // For ICU templates you must always use UPPER_SNAKE_CASE for your placeholder names.
+    // This matches the way the placeholder names are formatted in the XMB/XTB files.
+    // Note that `goog.getMsg()` requires lowerCamelCase for placeholder names, but
+    // actually converts them to UPPER_SNAKE_CASE when storing them in XMB and must convert
+    // the UPPER_SNAKE_CASE to lowerCamelCase when reading from XTB files. We want to avoid
+    // this needless complication for `declareIcuTemplate()` message declarations.
+    extractMessages(
+        lines(
+            "const MSG_ICU_EXAMPLE = declareIcuTemplate(",
+            "    'Email: {USER_EMAIL}',",
+            "    {",
+            "      description: 'Labeled email address',",
+            "      example: {",
+            "        'USER_EMAIL': '[email protected]',",
+            "      }",
+            "    });",
+            ""));
+    final ImmutableList<JSError> actualErrors = compiler.getErrors();
+    assertThat(actualErrors).isEmpty();
+    assertThat(compiler.getWarnings()).isEmpty();
+    assertThat(messages).hasSize(1);
+    JsMessage jsMessage = messages.get(0);
+    assertThat(jsMessage.canonicalPlaceholderNames()).containsExactly("USER_EMAIL");
+  }
+
+  @Test
+  public void testIcuTemplatePlaceholderLowerCamelCase() {
+    // For ICU templates you must always use UPPER_SNAKE_CASE for your placeholder names.
+    // This matches the way the placeholder names are formatted in the XMB/XTB files.
+    // Note that `goog.getMsg()` requires lowerCamelCase for placeholder names, but
+    // actually converts them to UPPER_SNAKE_CASE when storing them in XMB and must convert
+    // the UPPER_SNAKE_CASE to lowerCamelCase when reading from XTB files. We want to avoid
+    // this needless complication for `declareIcuTemplate()` message declarations.
+    extractMessages(
+        lines(
+            "const MSG_ICU_EXAMPLE = declareIcuTemplate(",
+            "    'Email: {userEmail}',", // should be USER_EMAIL
+            "    {",
+            "      description: 'Labeled email address',",
+            "      example: {",
+            "        'userEmail': '[email protected]',", // should be USER_EMAIL
+            "      }",
+            "    });",
+            ""));
+    final ImmutableList<JSError> actualErrors = compiler.getErrors();
+    assertThat(actualErrors)
+        .comparingElementsUsing(DIAGNOSTIC_EQUALITY)
+        .containsExactly(MESSAGE_TREE_MALFORMED);
+    assertThat(actualErrors)
+        .comparingElementsUsing(DESCRIPTION_EQUALITY)
+        .containsExactly(
+            "Message parse tree malformed. Placeholder not in UPPER_SNAKE_CASE: userEmail");
+    assertThat(compiler.getWarnings()).isEmpty();
+    // The malformed message is skipped.
+    assertThat(messages).isEmpty();
+  }
+
   @Test
   public void testJsMessageOnVar() {
     extractMessagesSafely("/** @desc Hello */ var MSG_HELLO = goog.getMsg('a')");