Backmerge: #5848 - Unable to establish connection between micro structure and sugar or phopshate (and partially - unresolved monomer)

packages/ketcher-core/src/application/render/renderers/BondRenderer.ts

@@ -198,7 +198,7 @@ export class BondRenderer extends BaseRenderer {
 
   private appendRootElement() {
     return this.canvas
-      .append('g')
+      .insert('g', ':first-child')
       .data([this])
       .attr(
         'transform',

packages/ketcher-core/src/domain/entities/Phosphate.ts

@@ -12,13 +12,21 @@ export class Phosphate extends BaseMonomer {
   }
 
   public getValidSourcePoint(secondMonomer: BaseMonomer) {
+    if (!secondMonomer) {
+      return this.firstFreeAttachmentPoint;
+    }
+
     return this.getValidPoint(
       secondMonomer,
       secondMonomer.potentialSecondAttachmentPointForBond,
     );
   }
 
   public getValidTargetPoint(firstMonomer: BaseMonomer) {
+    if (!firstMonomer) {
+      return this.firstFreeAttachmentPoint;
+    }
+
     // same implementation for both source and target attachment points
     return this.getValidPoint(
       firstMonomer,

packages/ketcher-core/src/domain/entities/Sugar.ts

@@ -9,14 +9,22 @@ import { isRnaBaseOrAmbiguousRnaBase } from 'domain/helpers/monomers';
 import { IVariantMonomer } from 'domain/entities/types';
 
 export class Sugar extends BaseMonomer {
-  public getValidSourcePoint(secondMonomer: BaseMonomer & IVariantMonomer) {
+  public getValidSourcePoint(secondMonomer?: BaseMonomer & IVariantMonomer) {
+    if (!secondMonomer) {
+      return this.firstFreeAttachmentPoint;
+    }
+
     return this.getValidPoint(
       secondMonomer,
       secondMonomer.potentialSecondAttachmentPointForBond,
     );
   }
 
   public getValidTargetPoint(firstMonomer: BaseMonomer & IVariantMonomer) {
+    if (!firstMonomer) {
+      return this.firstFreeAttachmentPoint;
+    }
+
     // same implementation for both source and target attachment points
     return this.getValidPoint(
       firstMonomer,

packages/ketcher-core/src/domain/entities/UnresolvedMonomer.ts

@@ -5,12 +5,20 @@ import { SubChainNode } from 'domain/entities/monomer-chains/types';
 import { Peptide } from 'domain/entities/Peptide';
 
 export class UnresolvedMonomer extends BaseMonomer {
-  public getValidSourcePoint(monomer?: BaseMonomer) {
-    return Peptide.prototype.getValidSourcePoint.call(this, monomer);
+  public getValidSourcePoint(secondMonomer?: BaseMonomer) {
+    if (!secondMonomer) {
+      return this.firstFreeAttachmentPoint;
+    }
+
+    return Peptide.prototype.getValidSourcePoint.call(this, secondMonomer);
   }
 
-  public getValidTargetPoint(monomer: BaseMonomer) {
-    return Peptide.prototype.getValidTargetPoint.call(this, monomer);
+  public getValidTargetPoint(firstMonomer: BaseMonomer) {
+    if (!firstMonomer) {
+      return this.firstFreeAttachmentPoint;
+    }
+
+    return Peptide.prototype.getValidTargetPoint.call(this, firstMonomer);
   }
 
   public get SubChainConstructor() {