Normalize whitespace

.editorconfig

@@ -0,0 +1,24 @@
+# Editor configuration, see http://editorconfig.org
+root = true
+
+[*]
+charset = utf-8
+indent_style = space
+indent_size = 4
+insert_final_newline = true
+trim_trailing_whitespace = true
+max_line_length = 80
+
+[*.sh]
+end_of_line = lf
+
+[*.java]
+indent_size = 4
+max_line_length = 120
+
+
+[*.yaml]
+indent_size = 2
+
+[*.yml]
+indent_size = 2

.git-blame-ignore-revs

@@ -0,0 +1,13 @@
+# Run this command to always ignore formatting commits in `git blame`
+# git config blame.ignoreRevsFile .git-blame-ignore-revs
+
+# replaced tabs with spaces
+8efd5a7227658bbcc5b46ba647d15edf42dc0302
+
+# removed trailing whitespace
+63917fec5f518cd66ebbf56903d5167ac1c815ab
+
+# normalize indentation
+4ca06f1346d13d6e275d891de918cc6bae85c3d8
+f3301743a5e4ca39b415e4f1fa32c66a39ef37b5
+

.github/workflows/build.yaml

@@ -25,6 +25,30 @@ jobs:
         name: Event File
         path: ${{ github.event_path }}
 
+
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }} # run it on the PR, not on the merged commit, for better line numbers
+
+      - uses: actions/setup-java@v4
+        with:
+          java-version: 11
+          distribution: 'temurin'
+          cache: 'maven'
+      - name: Run checkstyle and print errors
+        run: mvn -B checkstyle:checkstyle checkstyle:check
+      - name: Report build results
+        uses: gmazzo/publish-report-annotations@v1 # target latest major
+        if: ${{ !cancelled() }}
+        with:
+          testsSummary: off
+          reports: "target/checkstyle-result.xml"
+
+
+
   test:
     if: ${{ !(github.ref == 'refs/heads/main' && contains(github.event.head_commit.message, '[maven-release-plugin]')) }}
     strategy:
@@ -39,7 +63,7 @@ jobs:
           java-version: 11
           distribution: 'temurin'
           cache: 'maven'
-      
+
       - name: test
         run: mvn -B clean test
 
@@ -49,7 +73,7 @@ jobs:
         with:
           name: Unit Test Results (${{ matrix.os }})
           path: target/surefire-reports/**/*.xml
-        
+
   checker-framework:
     if: ${{ !(github.ref == 'refs/heads/main' && contains(github.event.head_commit.message, '[maven-release-plugin]')) }}
     runs-on: ubuntu-latest

checkstyle.xml

@@ -0,0 +1,58 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC
+          "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+          "https://checkstyle.org/dtds/configuration_1_3.dtd">
+<module name="Checker">
+   <!-- this checker only defines the things we really do not want, not all the warnings that checkstyle would also allow -->
+  <module name="SuppressWarningsFilter"/>
+  <property name="charset" value="UTF-8"/>
+  <property name="severity" value="error"/>
+  <property name="fileExtensions" value="java, properties, rsc, xml"/>
+
+  <!-- allow suppression of errors for certain files -->
+  <module name="SuppressionFilter">
+    <property name="file" value="checkstyle-suppressions.xml" />
+    <property name="optional" value="true"/>
+  </module>
+
+
+  <!-- Whitespace -->
+  <module name="FileTabCharacter"> <!-- no tabs -->
+    <property name="eachLine" value="true"/>
+  </module>
+  <module name="RegexpSingleline">
+    <property name="format" value="[^\s]\s+$"/> <!-- we only care about statements with trailing whitespace, empty lines with some whitespace we're not gointg to be picky about -->
+
+    <property name="message" value="Remove trailing whitespace" />
+    <property name="fileExtensions" value="xml, java, rsc"/>
+  </module>
+
+  <!-- java style things -->
+  <module name="TreeWalker">
+    <module name="OuterTypeFilename"/> <!-- make sure the name of the file is the same as the class -->
+    <module name="AvoidEscapedUnicodeCharacters">
+      <!-- avoid escapes of unicode chars where we can just write the unicode char in a string -->
+      <property name="allowEscapesForControlCharacters" value="true"/>
+      <property name="allowByTailComment" value="true"/>
+      <property name="allowNonPrintableEscapes" value="true"/>
+    </module>
+    <module name="NeedBraces"> <!-- make sure that {} are always required, also for single line statements -->
+      <property name="tokens" value="LITERAL_DO, LITERAL_ELSE, LITERAL_FOR, LITERAL_IF, LITERAL_WHILE"/>
+    </module>
+    <module name="OneStatementPerLine"/>
+    <module name="FallThrough"/> <!-- can be relieved by explicitly adding a comment that mentions fall[s]?through-->
+    <module name="ModifierOrder"/>
+    <module name="NoFinalizer"/>
+
+    <module name="Indentation"> <!-- make sure indents happen at a predictable pattern-->
+      <property name="basicOffset" value="4"/>
+      <property name="braceAdjustment" value="4"/>
+      <property name="caseIndent" value="4"/>
+      <property name="throwsIndent" value="4"/>
+      <property name="lineWrappingIndentation" value="4"/>
+      <property name="arrayInitIndent" value="4"/>
+    </module>
+
+  </module>
+
+</module>

pom.xml

@@ -164,6 +164,14 @@
 					</execution>
 				</executions>
 			</plugin>
+      <plugin> <!-- needs to be explictily envoked using mvn checkstyle:check -->
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-checkstyle-plugin</artifactId>
+        <version>3.5.0</version>
+        <configuration>
+          <configLocation>checkstyle.xml</configLocation>
+        </configuration>
+      </plugin>
 		</plugins>
 	</build>
 

src/main/java/io/usethesource/vallang/IBool.java

@@ -13,7 +13,7 @@
 import io.usethesource.vallang.visitors.IValueVisitor;
 
 public interface IBool extends IValue {
-	@Override
+    @Override
     default int getMatchFingerprint() {
         if (getValue()) {
             return 3569038; /* "true".hashCode() */
@@ -23,17 +23,17 @@ default int getMatchFingerprint() {
         }
     }
 
-	boolean getValue();
-	String getStringRepresentation();
-	IBool and(IBool other);
-	IBool or(IBool other);
-	IBool xor(IBool other);
-	IBool not();
-	IBool implies(IBool other);
-	IBool equivalent(IBool other);
-	
-	@Override
-	default <T, E extends Throwable> T accept(IValueVisitor<T, E> v) throws E {
-	    return v.visitBoolean(this);
-	}
+    boolean getValue();
+    String getStringRepresentation();
+    IBool and(IBool other);
+    IBool or(IBool other);
+    IBool xor(IBool other);
+    IBool not();
+    IBool implies(IBool other);
+    IBool equivalent(IBool other);
+
+    @Override
+    default <T, E extends Throwable> T accept(IValueVisitor<T, E> v) throws E {
+        return v.visitBoolean(this);
+    }
 }

src/main/java/io/usethesource/vallang/ICollection.java

@@ -15,19 +15,19 @@ public interface ICollection<T extends ICollection<T>> extends IValue, Iterable<
     public default Type getElementType() {
         return getType().getElementType();
     }
-    
+
     /**
      * @return true iff this container has no elements
      */
     public boolean isEmpty();
-    
+
     /**
      * @return an empty collection
      */
     public default T empty() {
         return writer().done();
     }
-    
+
     /**
      * @return an empty writer for this collection kind
      */
@@ -37,20 +37,20 @@ public default T empty() {
      * @return the arity of the collection (the number of elements in it)
      */
     public int size();
-    
+
     /**
      * @return this collection with an IRelation interface
      * @throws IllegalOperationException when the container does not contain all tuples of the same arity
      */
     public IRelation<T> asRelation();
-    
+
     /**
      * @return true iff the collection contains only tuples of a fixed width, if any.
      */
     public default boolean isRelation() {
         return getElementType().isFixedWidth();
     }
-    
+
     /**
      * Computes the Cartesian product of two collections
      * @param that is another collection
@@ -62,7 +62,7 @@ public default T product(T that) {
         if (that.isEmpty()) {
             return that;
         }
-        
+
         for (IValue t1 : this) {
             for (IValue t2 : that) {
                 w.appendTuple(t1, t2);
@@ -71,11 +71,11 @@ public default T product(T that) {
 
         return w.done();
     }
-    
+
     /**
      * Computes the union of two collections, ignoring duplicates. The original duplicates in the receiver and the given container will dissappear as well.
-     * 
-     * @param that is the other collection 
+     *
+     * @param that is the other collection
      * @return a collection containing both the elements of the receiver and those of the given container, without introducing  duplicates.
      */
     public default T union(T that) {
@@ -84,7 +84,7 @@ public default T union(T that) {
         w.appendAll(that);
         return w.done();
     }
-    
+
     /**
      * @return a stream of IValues from the current collection
      */