wip on fixing checker warnings

sources/src/main/java/org/apache/commons/text/translate/AggregateTranslator.java

@@ -16,6 +16,9 @@
  */
 package org.apache.commons.text.translate;
 
+import org.checkerframework.checker.index.qual.LTLengthOf;
+import org.checkerframework.checker.index.qual.NonNegative;
+
 import java.io.IOException;
 import java.io.Writer;
 import java.util.ArrayList;
@@ -53,7 +56,9 @@ public class AggregateTranslator extends CharSequenceTranslator {
      * {@inheritDoc}
      */
     @Override
-    public int translate(final CharSequence input, final int index, final Writer writer) throws IOException {
+    public int translate(final CharSequence input,
+                         final @NonNegative @LTLengthOf("#1") int index,
+                         final Writer writer) throws IOException {
         for (final CharSequenceTranslator translator : translators) {
             final int consumed = translator.translate(input, index, writer);
             if (consumed != 0) {

sources/src/main/java/org/apache/commons/text/translate/CharSequenceTranslator.java

@@ -23,6 +23,9 @@ import java.io.Writer;
 import java.util.Locale;
 
 import org.apache.commons.lang3.Validate;
+import org.checkerframework.checker.index.qual.LTLengthOf;
+import org.checkerframework.checker.index.qual.NonNegative;
+import org.checkerframework.checker.index.qual.Positive;
 
 /**
  * An API for translating text.
@@ -80,7 +83,9 @@ public abstract class CharSequenceTranslator {
      * @return int count of code points consumed
      * @throws IOException if and only if the Writer produces an IOException
      */
-    public abstract int translate(CharSequence input, int index, Writer writer) throws IOException;
+    public abstract int translate(CharSequence input,
+                                  @NonNegative @LTLengthOf("#1") int index,
+                                  Writer writer) throws IOException;
 
     /**
      * Translate an input onto a Writer. This is intentionally final as its algorithm is
@@ -116,8 +121,14 @@ public abstract class CharSequenceTranslator {
             }
             // contract with translators is that they have to understand code points
             // and they just took care of a surrogate pair
-            for (int pt = 0; pt < consumed; pt++) {
+            // Added pos < len as defensive condition for possibly buggy implementations of translate returning wrong
-                pos += Character.charCount(Character.codePointAt(input, pos));
+            // number of codepoints consumed
+            for (int pt = 0; pt < consumed && pos < len; pt++) {
+                int increment = Character.charCount(Character.codePointAt(input, pos));
+                assert pos + increment <= len : "@AssumeAssertion(index): increment corresponds to the number of bytes" +
+                        "of char codepoint at position index[pos]. Adding this quantity results in a valid index or in" +
+                        "the length of the string.";
+                pos += increment;
             }
         }
     }
@@ -130,8 +141,10 @@ public abstract class CharSequenceTranslator {
      * @return CharSequenceTranslator merging this translator with the others
      */
     public final CharSequenceTranslator with(final CharSequenceTranslator... translators) {
-        final CharSequenceTranslator[] newArray = new CharSequenceTranslator[translators.length + 1];
+        final @Positive int newArrayLen = translators.length + 1;
+        final CharSequenceTranslator[] newArray = new CharSequenceTranslator[newArrayLen];
         newArray[0] = this;
+        assert translators.length == newArray.length - 1 : "@AssumeAssertion(index): by construction of newArray and newArrayLen";
         System.arraycopy(translators, 0, newArray, 1, translators.length);
         return new AggregateTranslator(newArray);
     }

sources/src/main/java/org/apache/commons/text/translate/CodePointTranslator.java

@@ -16,6 +16,9 @@
  */
 package org.apache.commons.text.translate;
 
+import org.checkerframework.checker.index.qual.LTLengthOf;
+import org.checkerframework.checker.index.qual.NonNegative;
+
 import java.io.IOException;
 import java.io.Writer;
 
@@ -32,7 +35,9 @@ public abstract class CodePointTranslator extends CharSequenceTranslator {
      * {@inheritDoc}
      */
     @Override
-    public final int translate(final CharSequence input, final int index, final Writer writer) throws IOException {
+    public final int translate(final CharSequence input,
+                               final @NonNegative @LTLengthOf("#1") int index,
+                               final Writer writer) throws IOException {
         final int codePoint = Character.codePointAt(input, index);
         final boolean consumed = translate(codePoint, writer);
         return consumed ? 1 : 0;

sources/src/main/java/org/apache/commons/text/translate/CsvTranslators.java

@@ -58,14 +58,28 @@ public final class CsvTranslators {
 
         @Override
         void translateWhole(final CharSequence input, final Writer writer) throws IOException {
+            final int zeroIndex = 0;
+            final int oneIndex = 1;
+            final int lastIndex = input.length() - 1;
+            
+            // unfortunately there is no way to encode non-empty length
+            assert zeroIndex < input.length() && lastIndex >= 0 :
+                    "@AssumeAssertion(index): translateWhole is called by " +
+                    "SinglePassTranslator.translate(CharSequence, int, Writer), and that is part of a template method" +
+                    "implementation that by contract is called only with non-empty `input` CharSequences";
+
             // is input not quoted?
-            if (input.charAt(0) != CSV_QUOTE || input.charAt(input.length() - 1) != CSV_QUOTE) {
+            if (input.charAt(zeroIndex) != CSV_QUOTE || input.charAt(lastIndex) != CSV_QUOTE) {
                 writer.write(input.toString());
                 return;
             }
 
+            if (oneIndex >= input.length()) {
+                throw new IllegalArgumentException("input length should be at least 2");
+            }
+
             // strip quotes
-            final String quoteless = input.subSequence(1, input.length() - 1).toString();
+            final String quoteless = input.subSequence(oneIndex, lastIndex).toString();
 
             if (StringUtils.containsAny(quoteless, CSV_SEARCH_CHARS)) {
                 // deal with escaped quotes; ie) ""

sources/src/main/java/org/apache/commons/text/translate/UnicodeEscaper.java

@@ -128,11 +128,18 @@ public class UnicodeEscaper extends CodePointTranslator {
             writer.write(toUtf16Escape(codePoint));
         } else {
           writer.write("\\u");
-          writer.write(HEX_DIGITS[codePoint >> 12 & 15]);
+          writer.write(hexDigitsAccess(codePoint >> 12));
-          writer.write(HEX_DIGITS[codePoint >> 8 & 15]);
+          writer.write(hexDigitsAccess(codePoint >> 8));
-          writer.write(HEX_DIGITS[codePoint >> 4 & 15]);
+          writer.write(hexDigitsAccess(codePoint >> 4));
-          writer.write(HEX_DIGITS[codePoint & 15]);
+          writer.write(hexDigitsAccess(codePoint));
         }
         return true;
     }
+
+    private char hexDigitsAccess(final int index) {
+        int i = index & 15;
+        assert i >= 0 && i < HEX_DIGITS.length
+                : "@AssumeAssertion(index): bitwise and with 15 always produces numbers in [0,15]";
+        return HEX_DIGITS[i];
+    }
 }