add folding builder

src/main/java/org/nixos/idea/lang/NixFoldingBuilder.kt

@@ -0,0 +1,135 @@
+package org.nixos.idea.lang
+
+import com.intellij.lang.ASTNode
+import com.intellij.lang.folding.FoldingBuilderEx
+import com.intellij.lang.folding.FoldingDescriptor
+import com.intellij.openapi.editor.Document
+import com.intellij.psi.PsiComment
+import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiFile
+import com.intellij.util.containers.toArray
+import org.nixos.idea.psi.NixBindAttr
+import org.nixos.idea.psi.NixElementType
+import org.nixos.idea.psi.NixElementVisitor
+import org.nixos.idea.psi.NixExprApp
+import org.nixos.idea.psi.NixExprAssert
+import org.nixos.idea.psi.NixExprAttrs
+import org.nixos.idea.psi.NixExprIf
+import org.nixos.idea.psi.NixExprLambda
+import org.nixos.idea.psi.NixExprLet
+import org.nixos.idea.psi.NixExprList
+import org.nixos.idea.psi.NixExprOpConcat
+import org.nixos.idea.psi.NixExprOpUpdate
+import org.nixos.idea.psi.NixExprParens
+import org.nixos.idea.psi.NixExprSelect
+import org.nixos.idea.psi.NixExprWith
+import org.nixos.idea.psi.NixFormal
+import org.nixos.idea.psi.NixFormals
+import org.nixos.idea.psi.NixIndString
+import org.nixos.idea.psi.NixTypes
+
+class NixFoldingBuilder : FoldingBuilderEx() {
+    override fun buildFoldRegions(root: PsiElement, document: Document, quick: Boolean): Array<FoldingDescriptor> {
+        val descriptors = mutableListOf<FoldingDescriptor>()
+
+        root.accept(object : NixElementVisitor<Unit>() {
+            override fun visitExprAttrs(o: NixExprAttrs) {
+                o.acceptChildren(this)
+                descriptors.add(FoldingDescriptor(o, o.textRange))
+                o.bindList.forEach { it.accept(this) }
+            }
+
+            override fun visitBindAttr(o: NixBindAttr) {
+                o.expr?.accept(this)
+            }
+
+            override fun visitExprParens(o: NixExprParens) {
+                descriptors.add(FoldingDescriptor(o, o.textRange))
+                o.expr?.accept(this)
+            }
+
+            override fun visitExprWith(o: NixExprWith) {
+                o.exprList.forEach { it.accept(this) }
+            }
+
+            override fun visitExprApp(o: NixExprApp) {
+                o.exprList.forEach { it.accept(this) }
+            }
+
+            override fun visitExprIf(o: NixExprIf) {
+                o.acceptChildren(this)
+            }
+
+            override fun visitExprAssert(o: NixExprAssert) {
+                o.exprList.forEach { it.accept(this) }
+            }
+
+            override fun visitIndString(o: NixIndString) {
+                descriptors.add(FoldingDescriptor(o, o.textRange))
+            }
+
+            override fun visitExprOpUpdate(o: NixExprOpUpdate) {
+                o.acceptChildren(this)
+            }
+
+            override fun visitExprOpConcat(o: NixExprOpConcat) {
+                o.acceptChildren(this)
+            }
+
+            override fun visitExprList(o: NixExprList) {
+                descriptors.add(FoldingDescriptor(o, o.textRange))
+                o.items.forEach { it.accept(this) }
+            }
+
+            override fun visitExprSelect(o: NixExprSelect) {
+                o.acceptChildren(this)
+            }
+
+            override fun visitExprLet(o: NixExprLet) {
+                descriptors.add(FoldingDescriptor(o, o.textRange))
+                o.bindList.forEach { it.accept(this) }
+                o.expr?.accept(this)
+            }
+
+            override fun visitFormals(o: NixFormals) {
+                descriptors.add(FoldingDescriptor(o, o.textRange))
+                o.formalList.forEach { it.accept(this) }
+            }
+
+            override fun visitComment(comment: PsiComment) {
+                descriptors.add(FoldingDescriptor(comment, comment.textRange))
+            }
+
+            override fun visitFormal(o: NixFormal) {
+                o.expr?.accept(this)
+            }
+
+            override fun visitExprLambda(o: NixExprLambda) {
+                o.expr?.accept(this)
+                o.formals?.accept(this)
+            }
+
+            override fun visitFile(file: PsiFile) {
+                super.visitFile(file)
+                file.acceptChildren(this)
+            }
+        })
+
+        return descriptors.toArray(FoldingDescriptor.EMPTY_ARRAY)
+    }
+
+    override fun getPlaceholderText(node: ASTNode): String? =
+        when (node.elementType) {
+            NixTypes.EXPR_PARENS -> "(...)";
+            NixTypes.MCOMMENT -> "/* ... */";
+            NixTypes.EXPR_ATTRS -> "{ ... }";
+            NixTypes.EXPR_LIST -> "[ ... ]";
+            NixTypes.IND_STRING -> "'' ... ''";
+            NixTypes.FORMALS -> "{ ... }";
+            else -> null
+        }
+
+    override fun isCollapsedByDefault(node: ASTNode): Boolean {
+        return false
+    }
+}

src/main/resources/META-INF/plugin.xml

@@ -43,6 +43,10 @@
                 language="Nix"
                 implementationClass="org.nixos.idea.lang.NixCommenter"/>
 
+        <lang.foldingBuilder
+                language="Nix"
+                implementationClass="org.nixos.idea.lang.NixFoldingBuilder"/>
+
         <moveLeftRightHandler
                 language="Nix"
                 implementationClass="org.nixos.idea.lang.NixMoveElementLeftRightHandler"/>