#2178 Implement normalisation of grammar terms to support term compar…

…ison irrespective of metadata
fieldenms · Feb 23, 2024 · 76ad92a · 76ad92a
1 parent def3f3d
commit 76ad92a
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Showing 9 changed files with 59 additions and 2 deletions.
diff --git a/platform-eql-grammar/src/main/java/fielden/platform/bnf/OneOrMore.java b/platform-eql-grammar/src/main/java/fielden/platform/bnf/OneOrMore.java
@@ -11,4 +11,9 @@ public <V> OneOrMore annotate(TermMetadata.Key<V> key, V value) {
         return new OneOrMore(term, TermMetadata.merge(metadata(), key, value));
     }
 
+    @Override
+    public OneOrMore normalize() {
+        return new OneOrMore(term);
+    }
+
 }
diff --git a/platform-eql-grammar/src/main/java/fielden/platform/bnf/Optional.java b/platform-eql-grammar/src/main/java/fielden/platform/bnf/Optional.java
@@ -11,4 +11,9 @@ public <V> Optional annotate(TermMetadata.Key<V> key, V value) {
         return new Optional(term, TermMetadata.merge(metadata(), key, value));
     }
 
+    @Override
+    public Optional normalize() {
+        return new Optional(term);
+    }
+
 }
diff --git a/platform-eql-grammar/src/main/java/fielden/platform/bnf/Sequence.java b/platform-eql-grammar/src/main/java/fielden/platform/bnf/Sequence.java
@@ -25,6 +25,11 @@ public Sequence(Term... terms) {
         this(Arrays.asList(terms), TermMetadata.EMPTY_METADATA);
     }
 
+    @Override
+    public Term normalize() {
+        return new Sequence(terms);
+    }
+
     @Override
     public <V> Sequence annotate(final TermMetadata.Key<V> key, final V value) {
         return new Sequence(terms, TermMetadata.merge(metadata, key, value));

diff --git a/platform-eql-grammar/src/main/java/fielden/platform/bnf/Term.java b/platform-eql-grammar/src/main/java/fielden/platform/bnf/Term.java
@@ -5,6 +5,15 @@
  */
 public sealed interface Term permits Notation, Sequence, Symbol {
 
+    /**
+     * Returns this term in its normal form.
+     * The normal form doesn't include any metadata, making it possible to correctly compare terms irrespective of their
+     * metadata.
+     */
+    default Term normalize() {
+        return this;
+    }
+
     default TermMetadata metadata() {
         return TermMetadata.EMPTY_METADATA;
     }

diff --git a/platform-eql-grammar/src/main/java/fielden/platform/bnf/Terminal.java b/platform-eql-grammar/src/main/java/fielden/platform/bnf/Terminal.java
@@ -17,17 +17,28 @@ default Token rest(Class<?> varArityParameter) {
         return with(List.of(new VarArityParameter(varArityParameter)));
     }
 
+    @Override
+    default Terminal normalize() {
+        return this;
+    }
+
     @Override
     default <V> Terminal annotate(TermMetadata.Key<V> key, V value) {
         final var newMetadata = TermMetadata.merge(metadata(), key, value);
         final String name = name();
+        final Terminal normal = normalize();
 
         return new Terminal() {
             @Override
             public String name() {
                 return name;
             }
 
+            @Override
+            public Terminal normalize() {
+                return normal;
+            }
+
             @Override
             public TermMetadata metadata() {
                 return newMetadata;

diff --git a/platform-eql-grammar/src/main/java/fielden/platform/bnf/Token.java b/platform-eql-grammar/src/main/java/fielden/platform/bnf/Token.java
@@ -26,4 +26,9 @@ public boolean hasParameters() {
         return !parameters.isEmpty();
     }
 
+    @Override
+    public Token normalize() {
+        return new Token(name, TermMetadata.EMPTY_METADATA, parameters);
+    }
+
 }
diff --git a/platform-eql-grammar/src/main/java/fielden/platform/bnf/Variable.java b/platform-eql-grammar/src/main/java/fielden/platform/bnf/Variable.java
@@ -5,17 +5,28 @@
  */
 public non-sealed interface Variable extends Symbol {
 
+    @Override
+    default Variable normalize() {
+        return this;
+    }
+
     @Override
     default <V> Variable annotate(TermMetadata.Key<V> key, V value) {
         final var newMetadata = TermMetadata.merge(metadata(), key, value);
         final String name = name();
+        final Variable normal = normalize();
 
         return new Variable() {
             @Override
             public String name() {
                 return name;
             }
 
+            @Override
+            public Variable normalize() {
+                return normal;
+            }
+
             @Override
             public TermMetadata metadata() {
                 return newMetadata;

diff --git a/platform-eql-grammar/src/main/java/fielden/platform/bnf/ZeroOrMore.java b/platform-eql-grammar/src/main/java/fielden/platform/bnf/ZeroOrMore.java
@@ -11,4 +11,9 @@ public <V> ZeroOrMore annotate(TermMetadata.Key<V> key, V value) {
         return new ZeroOrMore(term, TermMetadata.merge(metadata(), key, value));
     }
 
+    @Override
+    public ZeroOrMore normalize() {
+        return new ZeroOrMore(term);
+    }
+
 }
diff --git a/platform-eql-grammar/src/main/java/fielden/platform/bnf/util/BnfVerifier.java b/platform-eql-grammar/src/main/java/fielden/platform/bnf/util/BnfVerifier.java
@@ -2,6 +2,7 @@
 
 import fielden.platform.bnf.BNF;
 import fielden.platform.bnf.Rule;
+import fielden.platform.bnf.Term;
 import fielden.platform.bnf.Variable;
 import org.apache.commons.collections4.CollectionUtils;
 
@@ -14,8 +15,8 @@
 public final class BnfVerifier {
 
     public static void verifyBnf(BNF bnf) {
-        var rhsVars = bnf.rules().stream().flatMap(BnfVerifier::ruleRhsVariables).collect(toSet());
-        var lhsVars = bnf.rules().stream().map(Rule::lhs).collect(toSet());
+        var rhsVars = bnf.rules().stream().flatMap(BnfVerifier::ruleRhsVariables).map(Variable::normalize).collect(toSet());
+        var lhsVars = bnf.rules().stream().map(Rule::lhs).map(Variable::normalize).collect(toSet());
         final Collection<Variable> diff = CollectionUtils.subtract(rhsVars, lhsVars);
         if (!diff.isEmpty()) {
             throw new RuntimeException("BNF uses non-terminals with no productions: { %s }".formatted(