Adds error coalescing

Author: TotalTechGeek

compiler.js

@@ -11,6 +11,7 @@ import {
 import asyncIterators from './async_iterators.js'
 import { coerceArray } from './utilities/coerceArray.js'
 import { countArguments } from './utilities/countArguments.js'
+import { downgrade } from './utilities/downgrade.js'
 
 /**
  * Provides a simple way to compile logic into a function that can be run.
@@ -307,12 +308,12 @@ function processBuiltString (method, str, buildState) {
     str = str.replace(`__%%%${x}%%%__`, item)
   })
 
-  const final = `(values, methods, notTraversed, asyncIterators, engine, above, coerceArray) => ${buildState.asyncDetected ? 'async' : ''} (context ${buildState.extraArguments ? ',' + buildState.extraArguments : ''}) => { let prev; const result = ${str}; return result }`
+  const final = `(values, methods, notTraversed, asyncIterators, engine, above, coerceArray, downgrade) => ${buildState.asyncDetected ? 'async' : ''} (context ${buildState.extraArguments ? ',' + buildState.extraArguments : ''}) => { let prev; const result = ${str}; return result }`
   // console.log(str)
-  // console.log(final)
+  console.log(final)
   // eslint-disable-next-line no-eval
   return Object.assign(
-    (typeof globalThis !== 'undefined' ? globalThis : global).eval(final)(values, methods, notTraversed, asyncIterators, engine, above, coerceArray), {
+    (typeof globalThis !== 'undefined' ? globalThis : global).eval(final)(values, methods, notTraversed, asyncIterators, engine, above, coerceArray, downgrade), {
       [Sync]: !buildState.asyncDetected,
       aboveDetected: typeof str === 'string' && str.includes(', above')
     })

defaultMethods.js

@@ -8,6 +8,7 @@ import { build, buildString } from './compiler.js'
 import chainingSupported from './utilities/chainingSupported.js'
 import InvalidControlInput from './errors/InvalidControlInput.js'
 import legacyMethods from './legacy.js'
+import { downgrade } from './utilities/downgrade.js'
 
 function isDeterministic (method, engine, buildState) {
   if (Array.isArray(method)) {
@@ -255,7 +256,7 @@ const defaultMethods = {
       let item
       for (let i = 0; i < arr.length; i++) {
         item = executeInLoop ? engine.run(arr[i], _1, { above: _2 }) : arr[i]
-        if (item !== null && item !== undefined) return item
+        if (downgrade(item) !== null && item !== undefined) return item
       }
 
       if (item === undefined) return null
@@ -269,7 +270,7 @@ const defaultMethods = {
       let item
       for (let i = 0; i < arr.length; i++) {
         item = executeInLoop ? await engine.run(arr[i], _1, { above: _2 }) : arr[i]
-        if (item !== null && item !== undefined) return item
+        if (downgrade(item) !== null && item !== undefined) return item
       }
 
       if (item === undefined) return null
@@ -278,8 +279,13 @@ const defaultMethods = {
     deterministic: (data, buildState) => isDeterministic(data, buildState.engine, buildState),
     compile: (data, buildState) => {
       if (!chainingSupported) return false
-      if (Array.isArray(data) && data.length) return `(${data.map((i) => buildString(i, buildState)).join(' ?? ')})`
-      return `(${buildString(data, buildState)}).reduce((a,b) => a ?? b, null)`
+      if (Array.isArray(data) && data.length) {
+        return `(${data.map((i, x) => {
+        if (Array.isArray(i) || !i || typeof i !== 'object' || x === data.length - 1) return buildString(i, buildState)
+        return 'downgrade(' + buildString(i, buildState) + ')'
+      }).join(' ?? ')})`
+      }
+      return `(${buildString(data, buildState)}).reduce((a,b) => downgrade(a) ?? b, null)`
     },
     traverse: false
   },

suites/errors.json

@@ -11,5 +11,17 @@
         "rule": { "!!": { "error": "Some error" } },
         "result": true,
         "data": null
+    },
+    {
+        "description": "Coalesce an error",
+        "rule": { "??": [{ "error": "Some error" }, 1] },
+        "result": 1,
+        "data": null
+    },
+    {
+        "description": "Coalesce an emitted error",
+        "rule": { "??": [{ "+": [{ "val": "hello" }]}, 1] },
+        "result": 1,
+        "data": { "hello": "world" }
     }
 ]

utilities/downgrade.js

@@ -0,0 +1,10 @@
+
+/**
+ * Used to make an "error" piece of data null, for the purposes of coalescing.
+ * @param {any} item
+ */
+export function downgrade (item) {
+  if (item && typeof item === 'object' && 'error' in item) return null
+  if (Number.isNaN(item)) return null
+  return item
+}