From 84a0d83efb926d5f78f8bd75b5e45f2ada627130 Mon Sep 17 00:00:00 2001
From: Vyacheslav Matyukhin <me@berekuk.ru>
Date: Wed, 22 Jun 2022 00:34:35 +0300
Subject: [PATCH] store location on RESyntaxError; export parse() function

---
 packages/squiggle-lang/src/js/index.ts        | 20 ++++++++++++++++++-
 .../rescript/Reducer/Reducer_ErrorValue.res   |  7 +++++--
 .../Reducer_Expression/Reducer_Expression.res |  2 +-
 .../Reducer_Peggy/Reducer_Peggy_Parse.res     |  6 +++++-
 .../src/rescript/TypescriptInterface.res      |  3 +++
 5 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/packages/squiggle-lang/src/js/index.ts b/packages/squiggle-lang/src/js/index.ts
index 592de8e3..74ca1d1d 100644
--- a/packages/squiggle-lang/src/js/index.ts
+++ b/packages/squiggle-lang/src/js/index.ts
@@ -10,6 +10,7 @@ import {
   evaluatePartialUsingExternalBindings,
   evaluateUsingOptions,
   foreignFunctionInterface,
+  parse as parseRescript,
 } from "../rescript/TypescriptInterface.gen";
 export {
   makeSampleSetDist,
@@ -31,7 +32,7 @@ import {
   convertRawToTypescript,
   lambdaValue,
 } from "./rescript_interop";
-import { result, resultMap, tag, tagged } from "./types";
+import { Ok, result, resultMap, tag, tagged } from "./types";
 import { Distribution, shape } from "./distribution";
 
 export { Distribution, resultMap, defaultEnvironment };
@@ -58,6 +59,23 @@ export function run(
   return resultMap(res, (x) => createTsExport(x, e));
 }
 
+export function parse(
+  squiggleString: string
+): result<null, Extract<errorValue, { tag: "RESyntaxError" }>> {
+  const maybeExpression = parseRescript(squiggleString);
+  if (maybeExpression.tag === "Ok") {
+    return Ok(null); // TODO - return AST
+  } else {
+    if (
+      typeof maybeExpression.value !== "object" ||
+      maybeExpression.value.tag !== "RESyntaxError"
+    ) {
+      throw new Error("Expected syntax error");
+    }
+    return { tag: "Error", value: maybeExpression.value };
+  }
+}
+
 // Run Partial. A partial is a block of code that doesn't return a value
 export function runPartial(
   squiggleString: string,
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res
index 721fbc40..beaee7f7 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_ErrorValue.res
@@ -1,3 +1,6 @@
+@gentype.import("peggy") @genType.as("LocationRange")
+type location
+
 @genType
 type errorValue =
   | REArityError(option<string>, int, int) //TODO: Binding a lambda to a variable should record the variable name in lambda for error reporting
@@ -14,7 +17,7 @@ type errorValue =
   | REOperationError(Operation.operationError)
   | RERecordPropertyNotFound(string, string)
   | RESymbolNotFound(string)
-  | RESyntaxError(string)
+  | RESyntaxError(string, option<location>)
   | RETodo(string) // To do
   | REUnitNotFound(string)
 
@@ -50,7 +53,7 @@ let errorToString = err =>
   | RENotAFunction(valueString) => `${valueString} is not a function`
   | RERecordPropertyNotFound(msg, index) => `${msg}: ${index}`
   | RESymbolNotFound(symbolName) => `${symbolName} is not defined`
-  | RESyntaxError(desc) => `Syntax Error: ${desc}`
+  | RESyntaxError(desc, _) => `Syntax Error: ${desc}`
   | RETodo(msg) => `TODO: ${msg}`
   | REExpectedType(typeName) => `Expected type: ${typeName}`
   | REUnitNotFound(unitName) => `Unit not found: ${unitName}`
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
index 6b4168c3..dabe3150 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
@@ -157,7 +157,7 @@ let evaluatePartialUsingExternalBindings = (
   switch rAnswer {
   | Ok(EvRecord(externalBindings)) => Ok(externalBindings)
   | Ok(_) =>
-    Error(Reducer_ErrorValue.RESyntaxError(`Partials must end with an assignment or record`))
+    Error(Reducer_ErrorValue.RESyntaxError(`Partials must end with an assignment or record`, None))
   | Error(err) => err->Error
   }
 }
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.res
index 5bdcda14..1a37ccc0 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Peggy/Reducer_Peggy_Parse.res
@@ -5,11 +5,15 @@ type node = {"type": string}
 
 @module("./Reducer_Peggy_GeneratedParser.js") external parse__: string => node = "parse"
 
+let syntaxErrorToLocation: Js.Exn.t => Reducer_ErrorValue.location = error => %raw(`error.location`)
+
+@genType
 let parse = (expr: string): result<node, errorValue> =>
   try {
     Ok(parse__(expr))
   } catch {
-  | Js.Exn.Error(obj) => REJavaScriptExn(Js.Exn.message(obj), Js.Exn.name(obj))->Error
+  | Js.Exn.Error(obj) =>
+    RESyntaxError(Belt.Option.getExn(Js.Exn.message(obj)), syntaxErrorToLocation(obj)->Some)->Error
   }
 
 type nodeBlock = {...node, "statements": array<node>}
diff --git a/packages/squiggle-lang/src/rescript/TypescriptInterface.res b/packages/squiggle-lang/src/rescript/TypescriptInterface.res
index 932edaa1..5bc913d8 100644
--- a/packages/squiggle-lang/src/rescript/TypescriptInterface.res
+++ b/packages/squiggle-lang/src/rescript/TypescriptInterface.res
@@ -40,6 +40,9 @@ let evaluate = Reducer.evaluate
 @genType
 let evaluateUsingOptions = Reducer.evaluateUsingOptions
 
+@genType
+let parse = Reducer_Peggy_Parse.parse
+
 @genType
 let evaluatePartialUsingExternalBindings = Reducer.evaluatePartialUsingExternalBindings