From 7c6dbe017f03b99776f083fd99cad1f707ddca2f Mon Sep 17 00:00:00 2001
From: Matt Kantor <the.matt.kantor@gmail.com>
Date: Thu, 2 Jan 2025 10:21:48 -0500
Subject: [PATCH] Use plz notation in error messages

---
 src/language/semantics/key-path.ts       | 12 +++++++++++-
 src/language/semantics/semantic-graph.ts | 14 +++++++++++++-
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/language/semantics/key-path.ts b/src/language/semantics/key-path.ts
index 104b455..3ed7e33 100644
--- a/src/language/semantics/key-path.ts
+++ b/src/language/semantics/key-path.ts
@@ -1,4 +1,7 @@
+import { either } from '../../adts.js'
 import type { Atom, Molecule } from '../parsing.js'
+import { unparse } from '../unparsing.js'
+import { prettyPlz } from '../unparsing/pretty-plz.js'
 
 export const functionParameter = Symbol('functionParameter')
 export const functionReturn = Symbol('functionReturn')
@@ -15,7 +18,14 @@ export type KeyPath = readonly (
 )[]
 
 export const stringifyKeyPathForEndUser = (keyPath: KeyPath): string =>
-  JSON.stringify(keyPath)
+  either.match(
+    // TODO: Use single-line plz notation.
+    unparse(keyPathToMolecule(keyPath), prettyPlz),
+    {
+      right: stringifiedOutput => stringifiedOutput,
+      left: error => `(unserializable key path: ${error.message})`,
+    },
+  )
 
 export const keyPathToMolecule = (keyPath: KeyPath): Molecule =>
   Object.fromEntries(
diff --git a/src/language/semantics/semantic-graph.ts b/src/language/semantics/semantic-graph.ts
index 63776f0..665fccb 100644
--- a/src/language/semantics/semantic-graph.ts
+++ b/src/language/semantics/semantic-graph.ts
@@ -6,6 +6,8 @@ import type {
 } from '../errors.js'
 import type { Atom, Molecule } from '../parsing.js'
 import type { Canonicalized } from '../parsing/syntax-tree.js'
+import { unparse } from '../unparsing.js'
+import { prettyPlz } from '../unparsing/pretty-plz.js'
 import { serializeFunctionNode, type FunctionNode } from './function-node.js'
 import { stringifyKeyPathForEndUser, type KeyPath } from './key-path.js'
 import {
@@ -174,7 +176,17 @@ export const serialize = (
 
 export const stringifySemanticGraphForEndUser = (
   graph: SemanticGraph,
-): string => JSON.stringify(serialize(graph))
+): string =>
+  either.match(
+    either.flatMap(serialize(graph), output =>
+      // TODO: Use single-line plz notation.
+      unparse(output, prettyPlz),
+    ),
+    {
+      right: stringifiedOutput => stringifiedOutput,
+      left: error => `(unserializable value: ${error.message})`,
+    },
+  )
 
 export const isSemanticGraph = (
   value: