make AST traverial more robust and easier to understand

build.gradle

@@ -1,7 +1,7 @@
 apply plugin: 'groovy'
 apply plugin: 'maven'
 
-version = '0.6'
+version = '0.7'
 
 group = 'com.github.dfrommi'
 

src/integration-test/groovy/com/github/dfrommi/pandoc/PandocFilterSpec.groovy

@@ -7,7 +7,6 @@ import com.github.dfrommi.pandoc.types.HorizontalRule
 import com.github.dfrommi.pandoc.types.Para
 import com.github.dfrommi.pandoc.types.Space
 import com.github.dfrommi.pandoc.types.Str
-import spock.lang.IgnoreRest
 import spock.lang.Shared
 import spock.lang.Specification
 import spock.lang.Unroll
@@ -29,7 +28,7 @@ class PandocFilterSpec extends Specification {
 		System.out = oldSystemOut
 	}
 
-  @Unroll @IgnoreRest
+  @Unroll //@IgnoreRest
   def "toJSONFilter transformation #action elements"() {
     given:
     String input = converter.mdToJsonText(mdInput)
@@ -45,19 +44,19 @@ class PandocFilterSpec extends Specification {
     String result = outContent.toString()
     def actualJson = converter.jsonTextToJson(result)
 
-    expectedJson == actualJson
+    actualJson == expectedJson
 
     where:
     [action, mdInput, mdExpectedResult, transformation] << [
-//      ["replaces", "Hello world", "HELLO WORLD", { if(it in Str) new Str(it.text.toUpperCase()) }],
-//      ["removes text", "Hello world", "Hello", { if((it in Str && it.text == "world") || it in Space) []} ],
-//      ["adds", "Hello world", "Good morning world", { if (it in Str && it.text == "Hello") [new Str("Good"), new Space(), new Str("morning")] }],
-      ["replaces multiple", "# Some header\n\nSome text,", "Header line 1\nHeader line 2", { if(it in Header) [new Para(new Str("Header line 1")), new Para(new Str("Header line 2"))] }],
-//      ["removes","# Header\n\nSome text.\n\n-----\n\nSome more text", "# Header\n\nSome text.\n\nSome more text", {if(it in HorizontalRule) [] } ]
+      ["replaces", "Hello world", "HELLO WORLD", { if(it in Str) new Str(it.text.toUpperCase()) }],
+      ["removes text", "Hello world", "Hello", { if((it in Str && it.text == "world") || it in Space) []} ],
+      ["adds", "Hello world", "Good morning world", { if (it in Str && it.text == "Hello") [new Str("Good"), new Space(), new Str("morning")] }],
+      ["replaces multiple", "# Some header\n\nSome text", "Header1\n\nHeader2\n\nSome text", { if(it in Header) [new Para(new Str("Header1")), new Para(new Str("Header2"))] }],
+      ["removes","# Header\n\nSome text.\n\n-----\n\nSome more text", "# Header\n\nSome text.\n\nSome more text", {if(it in HorizontalRule) [] } ]
     ]
   }
 
-  def "toJSONFilter processes elements in correct sequence"() {
+  def "toJSONFilter processes elements in DFS sequence"() {
     given:
     String input = converter.mdToJsonText(mdInput)
     def classSequence = []
@@ -75,30 +74,30 @@ class PandocFilterSpec extends Specification {
     where:
     mdInput | expectedSequence
     "Hello world" | [Para, Str, Space, Str]
-    "# Header\n\nSome paragraph\n\n```\nSome code\n```\n" | [Header, Para, CodeBlock, Str /*from header*/, Str, Space, Str]
+    "# Header\n\nSome paragraph\n\n```\nSome code\n```\n" | [Header, Str, Para, Str, Space, Str, CodeBlock]
   }
 
-  def "toJSONFilter transformation copies elements"() {
+  @Unroll
+  def "toJSONFilter transformation of test document #i transforms successfully"() {
     given:
-			String mdInput = this.getClass().getResourceAsStream("/test-${i}.md").text
-			String input = converter.mdToJsonText(mdInput)
-      def expectedJson = converter.jsonTextToJson(input)
-
-      def outContent = hijackStreams(input)
+    String mdInput = this.getClass().getResourceAsStream("/test-${i}.md").text
+    String input = converter.mdToJsonText(mdInput)
+    def expectedJson = converter.jsonTextToJson(input)
+    def outContent = hijackStreams(input)
 
     when:
-			filter.toJSONFilter { elem ->
-				elem
-			}
+    filter.toJSONFilter { elem ->
+      elem
+    }
 
     then:
-			String result = outContent.toString()
-      def actualJson = converter.jsonTextToJson(result)
+    String result = outContent.toString()
+    def actualJson = converter.jsonTextToJson(result)
 
-      expectedJson == actualJson
+    actualJson == expectedJson
 
     where:
-      i << (1..13)
+    i << (1..13)
 	}
 
   static private OutputStream hijackStreams(String inputText) {

src/main/groovy/com/github/dfrommi/pandoc/PandocFilter.groovy

@@ -2,6 +2,7 @@ package com.github.dfrommi.pandoc
 
 import com.github.dfrommi.pandoc.convert.PandocConverter
 import com.github.dfrommi.pandoc.types.PandocType
+import com.github.dfrommi.pandoc.util.Walkable
 
 class PandocFilter {
 	/**
@@ -90,45 +91,44 @@ class PandocFilter {
 	 * @param node current mode
 	 * @param meta Metadata object
 	 * @param action The action closure to perform on node objects
-	 * @return The modified node
+	 * @return The modified node, never `null`
 	 */
 	def walk(node, meta, action) {
-		def res
-		if(node in List) {
-			res = node.collect {
-				def transformedResult = callActionWithOptionalMeta(it, meta, action)
-        transformedResult
-			}.findAll { it != [] }
-		} else {
-			res = callActionWithOptionalMeta(node, meta, action)
-		}
+    // If list came in, list is also returned
+		if(isCollectionOrArray(node)) {
+      def nodeList = node as List
+      def transformedNodeList = nodeList.collectMany { // a single node can be replaced by multiple, therefore collectMany
+        def currentResult = walk(it, meta, action)
+        // Automatically flatten if one node has been replaced by multiple nodes
+        (!isCollectionOrArray(it) && isCollectionOrArray(currentResult)) ? currentResult as List : [currentResult]
+      }
+      return transformedNodeList
+    }
+
+    // Transformation of a single node
+
+    def transformedResult = callActionWithOptionalMeta(node, meta, action)
 
-		(res as List).each { currentRes ->
-      currentRes.children.each{ key, childValues ->
-        // key is property name
-        def replacedSingleByList = false
+    // `null` means no modification.
+    // Result [] (=removing element) is handled in the caller (see collectMany)
+    if (transformedResult == null) {
+      transformedResult = node
+    }
 
-        def walkResult
-        def childResult = childValues.collect { child ->
-          if (isCollectionOrArray(child)) {
-            walkResult = child.collect { walk(it, meta, action) }
-          } else {
-            walkResult = walk(child, meta, action)
-            // ?: not possible, because false has to return walkResult
-            if(walkResult in List && !(child in List)) {
-              replacedSingleByList = true
-            }
-          }
+    // Transform all children
 
-          walkResult != null ? walkResult : child
-        }
-        currentRes[key] = replacedSingleByList ? childResult.flatten() : childResult
+    // transformation can be one node or a node list, but never a deeply nested list
+    (transformedResult as List).each { Walkable transformedNode ->
+      transformedNode.children.each { propertyName, childValues ->
+        // key is the property name, value is the child or list of children
+        def childResult = walk(childValues, meta, action)
+        transformedNode."$propertyName" = childResult
       }
-		}
-	
-		res
+    }
+
+    transformedResult
 	}
-	
+
 	private callActionWithOptionalMeta(node, meta, action) {
 		def actionResult = hasMetaParam(action) ? action(node, meta) : action(node)
 		actionResult != null ? actionResult : node

src/main/groovy/com/github/dfrommi/pandoc/util/Walkable.groovy

@@ -10,7 +10,7 @@ trait Walkable {
 	 * Map of child objects
 	 * @return Map with property name as key and child value list as value
 	 */
-	def getChildren() {
+	Map<String, ?> getChildren() {
 		def children = [:]
 		AnnotationHelper.findAllFieldsWithAnnotation(this.class, Child).each { AnnotatedFieldInfo<Child> afi ->
 			children << [(afi.name): afi.getFieldValue(this)]