Implement parser error recovery for malformed attribute syntax

eo-parser/src/main/antlr4/org/eolang/parser/Eo.g4

@@ -43,6 +43,13 @@ object
 // Ends on the next line
 bound
     : commentOptional (application | ((method | just) oname) EOL)
+    | errorBound
+    ;
+
+// Error production to handle malformed bound objects
+// This specifically targets malformed attribute syntax like [x] +++ bad
+errorBound
+    : commentOptional LSQ NAME* RSQ SPACE PLUS PLUS (~EOL)* EOL innersOrEol?
     ;
 
 subMaster

eo-parser/src/main/java/org/eolang/parser/DrProgram.java

@@ -53,7 +53,7 @@ public Iterator<Directive> iterator() {
             .add("object")
             .attr(
                 "noNamespaceSchemaLocation xsi http://www.w3.org/2001/XMLSchema-instance",
-                DrProgram.schema()
+                schema()
             )
             .attr("version", Manifests.read("EO-Version"))
             .attr("revision", Manifests.read("EO-Revision"))

eo-parser/src/main/java/org/eolang/parser/EoErrorRecoveryStrategy.java

@@ -0,0 +1,66 @@
+/*
+ * SPDX-FileCopyrightText: Copyright (c) 2016-2025 Objectionary.com
+ * SPDX-License-Identifier: MIT
+ */
+package org.eolang.parser;
+
+import org.antlr.v4.runtime.DefaultErrorStrategy;
+import org.antlr.v4.runtime.Parser;
+import org.antlr.v4.runtime.RecognitionException;
+import org.antlr.v4.runtime.Token;
+import org.antlr.v4.runtime.TokenStream;
+
+/**
+ * Custom error recovery strategy for EO parser.
+ * When encountering errors in object declarations, skip to the next
+ * object at the same indentation level to allow parsing to continue.
+ *
+ * @since 0.1
+ */
+final class EoErrorRecoveryStrategy extends DefaultErrorStrategy {
+
+    @Override
+    public void recover(
+        final Parser recognizer,
+        final RecognitionException exc
+    ) {
+        final String rule = recognizer.getRuleInvocationStack().get(0);
+        final String[] names = recognizer.getRuleNames();
+        if (names[EoParser.RULE_bound].equals(rule)
+            || names[EoParser.RULE_object].equals(rule)) {
+            skipToNextObjectAtSameLevel(recognizer);
+        } else {
+            super.recover(recognizer, exc);
+        }
+    }
+
+    /**
+     * Skip tokens until we find the start of the next object
+     * at the same indentation level.
+     * @param recognizer The parser
+     */
+    private static void skipToNextObjectAtSameLevel(final Parser recognizer) {
+        final TokenStream tokens = recognizer.getInputStream();
+        int index = recognizer.getCurrentToken().getTokenIndex();
+        while (index < tokens.size()) {
+            final Token token = tokens.get(index);
+            if (token.getType() == Token.EOF) {
+                break;
+            }
+            if (token.getType() == EoParser.UNTAB) {
+                break;
+            }
+            if (token.getType() == EoParser.EOL && index + 1 < tokens.size()) {
+                final Token next = tokens.get(index + 1);
+                if (next.getType() == EoParser.LSQ) {
+                    recognizer.getInputStream().seek(index);
+                    return;
+                }
+            }
+            index = index + 1;
+        }
+        if (index < tokens.size()) {
+            recognizer.getInputStream().seek(index);
+        }
+    }
+}

eo-parser/src/main/java/org/eolang/parser/EoParserErrors.java

@@ -70,10 +70,10 @@ public void syntaxError(
         final String result;
         final String underlined;
         if (error instanceof NoViableAltException) {
-            result = EoParserErrors.impasse((Parser) recognizer);
+            result = impasse((Parser) recognizer);
             underlined = this.underlined(symbol, line, position);
         } else if (error instanceof InputMismatchException) {
-            result = EoParserErrors.mismatch((Parser) recognizer, msg);
+            result = mismatch((Parser) recognizer, msg);
             underlined = this.underlined(symbol, line, position);
         } else {
             result = msg;

eo-parser/src/main/java/org/eolang/parser/EoSyntax.java

@@ -140,7 +140,7 @@ public EoSyntax(final String ipt, final Train<Shift> transform) {
      * @param ipt The EO program to parse
      */
     public EoSyntax(final Input ipt) {
-        this(ipt, EoSyntax.CANONICAL);
+        this(ipt, CANONICAL);
     }
 
     /**

eo-parser/src/main/java/org/eolang/parser/MsgUnderlined.java

@@ -72,12 +72,12 @@ private String underline() {
         if (this.origin.isEmpty() || this.length <= 0 || this.from >= this.origin.length()) {
             result = "";
         } else if (this.from < 0) {
-            result = MsgUnderlined.repeat("^", this.origin.length());
+            result = repeat("^", this.origin.length());
         } else {
             result = String.format(
                 "%s%s",
-                MsgUnderlined.repeat(" ", this.from),
-                MsgUnderlined.repeat("^", Math.min(this.length, this.origin.length()))
+                repeat(" ", this.from),
+                repeat("^", Math.min(this.length, this.origin.length()))
             );
         }
         return result;

eo-parser/src/main/java/org/eolang/parser/ParsingError.java

@@ -28,7 +28,7 @@ final class ParsingError extends RuntimeException {
                     msg
                 ).formatted(),
                 new MsgUnderlined(
-                    ParsingError.line(ctx),
+                    line(ctx),
                     ctx.getStart().getCharPositionInLine(),
                     ctx.getText().length()
                 ).formatted()

eo-parser/src/main/java/org/eolang/parser/PhiSyntax.java

@@ -131,7 +131,7 @@ public PhiSyntax(final Text input) {
      * @param extra Extra directives to append
      */
     public PhiSyntax(final Text inpt, final Iterable<Directive> extra) {
-        this(inpt, extra, PhiSyntax.CANONICAL);
+        this(inpt, extra, CANONICAL);
     }
 
     /**

eo-parser/src/main/java/org/eolang/parser/StUnhex.java

@@ -31,32 +31,32 @@ final class StUnhex extends StEnvelope {
     static final Shift XNAV = new StSequence(
         StUnhex.class.getSimpleName(),
         new StXnav(
-            StUnhex.BYTES,
+            BYTES,
             xnav -> xnav.node().setTextContent(
                 xnav.element("o").text().orElse("")
             )
         ),
         new StXnav(
-            StUnhex.elements("number"),
+            elements("number"),
             xnav -> {
-                final double number = StUnhex.buffer(
-                    StUnhex.undash(xnav.element("o").text().orElse(""))
+                final double number = buffer(
+                    undash(xnav.element("o").text().orElse(""))
                 ).getDouble();
                 final Node node = xnav.node();
                 if (!Double.isNaN(number) && !Double.isInfinite(number)) {
-                    node.setTextContent(StUnhex.number(number));
+                    node.setTextContent(number(number));
                 }
             }
         ),
         new StXnav(
-            StUnhex.elements("string"),
+            elements("string"),
             xnav -> xnav.node().setTextContent(
                 String.format(
                     "\"%s\"",
                     StringEscapeUtils.escapeJava(
                         new String(
-                            StUnhex.buffer(
-                                StUnhex.undash(xnav.element("o").text().orElse(""))
+                            buffer(
+                                undash(xnav.element("o").text().orElse(""))
                             ).array(),
                             StandardCharsets.UTF_8
                         )
@@ -70,7 +70,7 @@ final class StUnhex extends StEnvelope {
      * Ctor.
      */
     StUnhex() {
-        this(StUnhex.XNAV);
+        this(XNAV);
     }
 
     /**

eo-parser/src/main/java/org/eolang/parser/StrictXmir.java

@@ -82,7 +82,7 @@ public StrictXmir(final XML before, final Path tmp) {
             new Synced<>(
                 new Sticky<>(
                     () -> new StrictXML(
-                        StrictXmir.reset(before, tmp)
+                        reset(before, tmp)
                     )
                 )
             )
@@ -158,7 +158,7 @@ private static XML reset(final XML xml, final Path tmp) {
             if (before.startsWith("http")) {
                 after = String.format(
                     "file:///%s",
-                    StrictXmir.fetch(
+                    fetch(
                         before,
                         tmp.resolve(
                             before.substring(before.lastIndexOf('/') + 1)
@@ -190,10 +190,10 @@ private static XML reset(final XML xml, final Path tmp) {
      */
     private static File fetch(final String uri, final Path path, final Path tmp) {
         final File ret;
-        if (StrictXmir.MINE.equals(uri)) {
-            ret = StrictXmir.copied(uri, path, tmp);
+        if (MINE.equals(uri)) {
+            ret = copied(uri, path, tmp);
         } else {
-            ret = StrictXmir.downloaded(uri, path, tmp);
+            ret = downloaded(uri, path, tmp);
         }
         return ret;
     }

eo-parser/src/main/java/org/eolang/parser/TrStepped.java

@@ -45,7 +45,7 @@ final class TrStepped extends TrEnvelope {
      * @param train Original train
      */
     TrStepped(final Train<Shift> train) {
-        this(train, TrStepped.STEPPED);
+        this(train, STEPPED);
     }
 
     /**

eo-parser/src/main/java/org/eolang/parser/XeEoListener.java

@@ -175,6 +175,16 @@ public void exitBound(final EoParser.BoundContext ctx) {
         // Nothing here
     }
 
+    @Override
+    public void enterErrorBound(final EoParser.ErrorBoundContext ctx) {
+        // Nothing here
+    }
+
+    @Override
+    public void exitErrorBound(final EoParser.ErrorBoundContext ctx) {
+        // Nothing here
+    }
+
     @Override
     public void enterSubMaster(final EoParser.SubMasterContext ctx) {
         // Nothing here
@@ -954,7 +964,7 @@ public void enterData(final EoParser.DataContext ctx) {
                 final int indent = ctx.getStart().getCharPositionInLine();
                 data = new BytesToHex(
                     StringEscapeUtils.unescapeJava(
-                        XeEoListener.trimMargin(text, indent)
+                        trimMargin(text, indent)
                     ).getBytes(StandardCharsets.UTF_8)
                 );
             }

eo-parser/src/main/java/org/eolang/parser/XePhiListener.java

@@ -165,7 +165,7 @@ public void enterFormation(final PhiParser.FormationContext ctx) {
     @Override
     public void exitFormation(final PhiParser.FormationContext ctx) {
         this.properties.pop();
-        if (!this.properties.empty() && !XePhiListener.hasLambdaPackage(ctx.bindings())) {
+        if (!this.properties.empty() && !hasLambdaPackage(ctx.bindings())) {
             this.objects().leave();
         }
     }
@@ -202,15 +202,15 @@ public void exitScoped(final PhiParser.ScopedContext ctx) {
     @Override
     public void enterBindings(final PhiParser.BindingsContext ctx) {
         this.anames.push(new HashSet<>());
-        if (XePhiListener.hasLambdaPackage(ctx)) {
+        if (hasLambdaPackage(ctx)) {
             this.packages.add(this.attributes.peek());
             this.objs.add(new Objects());
         }
     }
 
     @Override
     public void exitBindings(final PhiParser.BindingsContext ctx) {
-        if (XePhiListener.hasLambdaPackage(ctx)) {
+        if (hasLambdaPackage(ctx)) {
             this.objs.poll();
         }
         this.anames.pop();
@@ -303,7 +303,7 @@ public void exitAttribute(final PhiParser.AttributeContext ctx) {
     public void enterFullAttribute(final PhiParser.FullAttributeContext ctx) {
         if (ctx.attribute() == null) {
             this.attributes.push(
-                String.format("%s%s", XePhiListener.ALPHA, ctx.getText().substring(1))
+                String.format("%s%s", ALPHA, ctx.getText().substring(1))
             );
         }
     }
@@ -346,7 +346,7 @@ public void exitDeltaBinding(final PhiParser.DeltaBindingContext ctx) {
 
     @Override
     public void enterLambdaBinding(final PhiParser.LambdaBindingContext ctx) {
-        if (!XePhiListener.LAMBDA_PACKAGE.equals(ctx.FUNCTION().getText())) {
+        if (!LAMBDA_PACKAGE.equals(ctx.FUNCTION().getText())) {
             this.objects().start(ctx).prop("name", "λ").leave();
             this.checkDuplicates(ctx, "λ");
         }
@@ -395,7 +395,7 @@ public void enterJustObject(final PhiParser.JustObjectContext ctx) {
         final int index = this.alphas.peek();
         this.alphas.pop();
         this.alphas.push(index + 1);
-        this.attributes.push(String.format("%s%d", XePhiListener.ALPHA, index));
+        this.attributes.push(String.format("%s%d", ALPHA, index));
     }
 
     @Override
@@ -541,7 +541,7 @@ private static boolean hasLambdaPackage(final PhiParser.BindingsContext ctx) {
                 context -> context.lambdaBinding() != null && context.lambdaBinding()
                     .FUNCTION()
                     .getText()
-                    .equals(XePhiListener.LAMBDA_PACKAGE)
+                    .equals(LAMBDA_PACKAGE)
             );
     }
 

eo-parser/src/main/java/org/eolang/parser/Xmir.java

@@ -134,15 +134,15 @@ public Collection<SAXParseException> validate(final XML xsd) {
      * @return EO representation as {@link String}
      */
     public String toEO() {
-        return this.converted(Xmir.FOR_EO, "eo");
+        return this.converted(FOR_EO, "eo");
     }
 
     /**
      * Converts XMIR to PHI.
      * @return PHI representation as {@link String}
      */
     public String toPhi() {
-        return this.converted(Xmir.FOR_PHI, "phi");
+        return this.converted(FOR_PHI, "phi");
     }
 
     /**