From 3957edb74fcf28ef4b6b983281dd80bba8fcd63c Mon Sep 17 00:00:00 2001
From: Benjie Gillam <benjie@jemjie.com>
Date: Tue, 30 Apr 2024 11:04:29 +0100
Subject: [PATCH] Overhaul printing of flagged values

---
 grafast/grafast/src/error.ts        | 21 +++++++++++++++++++++
 grafast/grafast/src/steps/__flag.ts | 11 ++++-------
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/grafast/grafast/src/error.ts b/grafast/grafast/src/error.ts
index f18c48cb70..03b8607b24 100644
--- a/grafast/grafast/src/error.ts
+++ b/grafast/grafast/src/error.ts
@@ -1,3 +1,4 @@
+import { inspect } from "./inspect.js";
 import type { ExecutionEntryFlags } from "./interfaces.js";
 import {
   $$safeError,
@@ -18,6 +19,17 @@ export interface FlaggedValue<TValue = any> {
   flags: ExecutionEntryFlags;
   value: TValue;
   planId: number | null;
+  toString(): string;
+}
+
+function flaggedValueToString(this: FlaggedValue) {
+  if (this.flags & FLAG_ERROR && this.value instanceof Error) {
+    return String(this.value);
+  } else if (this.flags & FLAG_INHIBITED && this.value === null) {
+    return "INHIBIT";
+  } else {
+    return `${this.flags}/${inspect(this.value)}`;
+  }
 }
 
 function flaggedValue<T>(
@@ -25,11 +37,20 @@ function flaggedValue<T>(
   value: any,
   planId: null | number,
 ): FlaggedValue<T> {
+  if (value === null && !(flags & FLAG_NULL)) {
+    throw new Error(`flaggedValue called with null, but not flagged as null.`);
+  }
+  if (value === null && !(flags & FLAG_INHIBITED)) {
+    throw new Error(
+      `flaggedValue called with null, but not flagged as inhibited.`,
+    );
+  }
   return {
     [$$flagged]: true,
     flags,
     value,
     planId,
+    toString: flaggedValueToString,
   };
 }
 
diff --git a/grafast/grafast/src/steps/__flag.ts b/grafast/grafast/src/steps/__flag.ts
index 3730aa4e4e..8fb06895c4 100644
--- a/grafast/grafast/src/steps/__flag.ts
+++ b/grafast/grafast/src/steps/__flag.ts
@@ -1,5 +1,5 @@
 import type { FlaggedValue } from "../error.js";
-import { $$inhibit, flagError, SafeError } from "../error.js";
+import { $$inhibit, flagError, isFlaggedValue, SafeError } from "../error.js";
 import { inspect } from "../inspect.js";
 import type {
   AddDependencyOptions,
@@ -138,12 +138,9 @@ export class __FlagStep<TData> extends ExecutableStep<TData> {
   }
   public toStringMeta(): string | null {
     const acceptFlags = ALL_FLAGS & ~this.forbiddenFlags;
-    const rej =
-      this.onRejectReturnValue === $$inhibit
-        ? `INHIBIT`
-        : this.onRejectReturnValue
-        ? trim(String(this.onRejectReturnValue))
-        : inspect(this.onRejectReturnValue);
+    const rej = this.onRejectReturnValue
+      ? trim(String(this.onRejectReturnValue))
+      : inspect(this.onRejectReturnValue);
     const $if =
       this.ifDep !== null ? this.getDepOptions(this.ifDep).step : null;
     return `${this.dependencies[0].id}, ${