Allow setting multiple many-to-many relationships

packages/builder/src/components/backend/Datasources/CreateEditRelationship.svelte

@@ -65,7 +65,7 @@
   let tableOptions
   let errorChecker = new RelationshipErrorChecker(
     invalidThroughTable,
-    relationshipExists
+    manyToManyRelationshipExistsFn
   )
   let errors = {}
   let fromPrimary, fromForeign, fromColumn, toColumn
@@ -125,7 +125,7 @@
     }
     return false
   }
-  function relationshipExists() {
+  function manyToManyRelationshipExistsFn() {
     if (
       originalFromTable &&
       originalToTable &&
@@ -141,16 +141,14 @@
       datasource.entities[getTable(toId).name].schema
     ).filter(value => value.through)
 
-    const matchAgainstUserInput = (fromTableId, toTableId) =>
-      (fromTableId === fromId && toTableId === toId) ||
-      (fromTableId === toId && toTableId === fromId)
+    const matchAgainstUserInput = link =>
+      (link.throughTo === throughToKey &&
+        link.throughFrom === throughFromKey) ||
+      (link.throughTo === throughFromKey && link.throughFrom === throughToKey)
 
-    return !!fromThroughLinks.find(from =>
-      toThroughLinks.find(
-        to =>
-          from.through === to.through &&
-          matchAgainstUserInput(from.tableId, to.tableId)
-      )
+    const allLinks = [...fromThroughLinks, ...toThroughLinks]
+    return !!allLinks.find(
+      link => link.through === throughId && matchAgainstUserInput(link)
     )
   }
 
@@ -181,16 +179,15 @@
       relationshipType: errorChecker.relationshipTypeSet(relationshipType),
       fromTable:
         errorChecker.tableSet(fromTable) ||
-        errorChecker.doesRelationshipExists() ||
         errorChecker.differentTables(fromId, toId, throughId),
       toTable:
         errorChecker.tableSet(toTable) ||
-        errorChecker.doesRelationshipExists() ||
         errorChecker.differentTables(toId, fromId, throughId),
       throughTable:
         errorChecker.throughTableSet(throughTable) ||
         errorChecker.throughIsNullable() ||
-        errorChecker.differentTables(throughId, fromId, toId),
+        errorChecker.differentTables(throughId, fromId, toId) ||
+        errorChecker.doesRelationshipExists(),
       throughFromKey:
         errorChecker.manyForeignKeySet(throughFromKey) ||
         errorChecker.manyTypeMismatch(

packages/builder/src/components/backend/Datasources/relationshipErrors.js

@@ -30,9 +30,9 @@ function typeMismatchCheck(fromTable, toTable, primary, foreign) {
 }
 
 export class RelationshipErrorChecker {
-  constructor(invalidThroughTableFn, relationshipExistsFn) {
+  constructor(invalidThroughTableFn, manyToManyRelationshipExistsFn) {
     this.invalidThroughTable = invalidThroughTableFn
-    this.relationshipExists = relationshipExistsFn
+    this.manyToManyRelationshipExists = manyToManyRelationshipExistsFn
   }
 
   setType(type) {
@@ -72,7 +72,7 @@ export class RelationshipErrorChecker {
   }
 
   doesRelationshipExists() {
-    return this.isMany() && this.relationshipExists()
+    return this.isMany() && this.manyToManyRelationshipExists()
       ? relationshipAlreadyExists
       : null
   }