Merge pull request #1 from larshisken/feat-improve-errors

feat: improve parse errors

Makefile

@@ -0,0 +1,15 @@
+.PHONY: clean
+
+unit_test_files := $(shell find test/unit/ -name '*.ts')
+
+coverage: $(unit_test_files) 
+	deno test --coverage=coverage --unstable test/unit
+
+coverage.lcov: coverage
+	deno coverage --unstable test/unit coverage --lcov > coverage.lcov
+
+coverage/html: coverage.lcov
+	genhtml --output-directory=coverage/html coverage.lcov
+
+clean:
+	rm --recursive --force coverage coverage.lcov

deps.ts

@@ -0,0 +1,5 @@
+export {
+  assert,
+  assertEquals,
+  assertThrows
+} from "https://deno.land/[email protected]/testing/asserts.ts";

mod.ts

@@ -175,10 +175,14 @@ function parse(template: string): Expression[] {
     if (length === index + 1 /* last char */) {
       if (
         char === "{" ||
-        cursor.over === ExpressionType.Variable && char !== "}"
+        (cursor.over === ExpressionType.Variable && char !== "}")
       ) {
-        throw new Error("ParseError");
+        throw new Error(
+          `Unexpected char '${char}' at position ${index +
+            1} in '${template}', expected a closing brace.`,
+        );
       }
+
       if (cursor.over === ExpressionType.Literal) {
         expressions.push({
           type: ExpressionType.Literal,
@@ -188,11 +192,18 @@ function parse(template: string): Expression[] {
       }
     }
 
-    if (
-      cursor.over === ExpressionType.Literal && char === "}" ||
-      cursor.over === ExpressionType.Variable && char === "{"
-    ) {
-      throw new Error("ParseError");
+    if (cursor.over === ExpressionType.Variable && char === "{") {
+      throw new Error(
+        `Unexpected char '{' at position ${index +
+          1} in '${template}', expected a closing brace.`,
+      );
+    }
+
+    if (cursor.over === ExpressionType.Literal && char === "}") {
+      throw new Error(
+        `Unexpected char '}' at position ${index +
+          1} in '${template}', expected an opening brace before a closing brace.`,
+      );
     }
 
     if (cursor.over === ExpressionType.Literal && char === "{") {
@@ -215,7 +226,10 @@ function parse(template: string): Expression[] {
     if (cursor.over === ExpressionType.Variable && char === "}") {
       if (index === cursor.pos + 1) {
         // braces are empty
-        throw new Error("ParseError");
+        throw new Error(
+          `Unexpected char '${template[index]}' at position ${index +
+            1} in '${template}', expected a pair of braces to have content.`,
+        );
       }
 
       const from = cursor.pos + 1;

test/integration/spec.test.ts

@@ -1,10 +1,6 @@
-import {
-  assert,
-  assertEquals,
-} from "https://deno.land/[email protected]/testing/asserts.ts";
-
-import { doTest, Example } from "./helper.ts";
+import { assert, assertEquals } from "../../deps.ts";
 import { expand } from "../../mod.ts";
+import { doTest, Example } from "./helper.ts";
 
 const [x, y] = await Promise.all([
   Deno.readTextFile("./uritemplate-test/spec-examples.json"),
@@ -19,7 +15,9 @@ const examples: Record<string, Example> = {
 doTest(
   examples,
   ({ testcase: [x, y], variables }) =>
-    typeof y === "string"
-      ? assertEquals(expand(x, variables), y)
-      : assert(y.includes(expand(x, variables))),
+    typeof y === "string" ? assertEquals(expand(x, variables), y) : assert(
+      y.includes(
+        expand(x, variables),
+      ),
+    ),
 );

test/unit/parse.test.ts

@@ -1,9 +1,5 @@
-import {
-  assertEquals,
-  assertThrows,
-} from "https://deno.land/[email protected]/testing/asserts.ts";
-
 import { Expression, ExpressionType, parse } from "../../mod.ts";
+import { assertEquals, assertThrows } from "../../deps.ts";
 
 Deno.test("Should parse '{foo}' to a list of expressions", () => {
   const expected: Expression[] = [
@@ -79,21 +75,57 @@ Deno.test("Should parse 'foo/{bar}/baz' to a list of expressions", () => {
 });
 
 Deno.test("Should throw when a closing brace is found without an opening brace", () => {
-  assertThrows(() => parse("}"), Error, "ParseError");
-  assertThrows(() => parse("foo}bar"), Error, "ParseError");
+  assertThrows(
+    () => parse("}"),
+    Error,
+    "Unexpected char '}' at position 1 in '}', expected an opening brace before a closing brace.",
+  );
+
+  assertThrows(
+    () => parse("foo}bar"),
+    Error,
+    "Unexpected char '}' at position 4 in 'foo}bar', expected an opening brace before a closing brace.",
+  );
 });
 
 Deno.test("Should throw when an opening brace is found at the end", () => {
-  assertThrows(() => parse("{"), Error, "ParseError");
-  assertThrows(() => parse("foo{"), Error, "ParseError");
+  assertThrows(
+    () => parse("{"),
+    Error,
+    "Unexpected char '{' at position 1 in '{', expected a closing brace.",
+  );
+
+  assertThrows(
+    () => parse("foo{"),
+    Error,
+    "Unexpected char '{' at position 4 in 'foo{', expected a closing brace.",
+  );
 });
 
 Deno.test("Should throw when an opening brace is not closed", () => {
-  assertThrows(() => parse("foo{bar"), Error, "ParseError");
-  assertThrows(() => parse("foo{bar{baz}"), Error, "ParseError");
+  assertThrows(
+    () => parse("foo{bar"),
+    Error,
+    "Unexpected char 'r' at position 7 in 'foo{bar', expected a closing brace.",
+  );
+
+  assertThrows(
+    () => parse("foo{bar{baz}"),
+    Error,
+    "Unexpected char '{' at position 8 in 'foo{bar{baz}', expected a closing brace.",
+  );
 });
 
 Deno.test("Should throw when empty braces are found", () => {
-  assertThrows(() => parse("{}"), Error, "ParseError");
-  assertThrows(() => parse("foo/{}"), Error, "ParseError");
+  assertThrows(
+    () => parse("{}"),
+    Error,
+    "Unexpected char '}' at position 2 in '{}', expected a pair of braces to have content.",
+  );
+
+  assertThrows(
+    () => parse("foo/{}"),
+    Error,
+    "Unexpected char '}' at position 6 in 'foo/{}', expected a pair of braces to have content.",
+  );
 });

test/unit/pct.test.ts

@@ -1,5 +1,4 @@
-import { assertEquals } from "https://deno.land/[email protected]/testing/asserts.ts";
-
+import { assertEquals } from "../../deps.ts";
 import { pctEncode, pctEncodeChar } from "../../pct.ts";
 
 Deno.test("Should encode individual characters", () => {