[PR #1323] [MERGED] Fix empty parethesized type unexpected error #1018

New Issue

2025-12-30T01:28:19+01:00

adam commented

2025-12-30 01:28:19 +01:00

📋 Pull Request Information

Original PR: https://github.com/apple/pkl/pull/1323
Author: @spyoungtech
Created: 11/18/2025
Status: ✅ Merged
Merged: 11/18/2025
Merged by: @stackoverflow

Base: main ← Head: fix-empty-parethesized-type-error

📝 Commits (4)

3c635a6 throw detailed error when parenthesized type is empty
6c69fa6 add test for empty parenthesized type annotation
5e45514 add new test to exceptions
5dde0e5 pass error location instead of backtracking

📊 Changes

4 files changed (+11 additions, -0 deletions)

View changed files

➕ pkl-core/src/test/files/LanguageSnippetTests/input/errors/emptyParenthesizedTypeAnnotation.pkl (+1 -0)
➕ pkl-core/src/test/files/LanguageSnippetTests/output/errors/emptyParenthesizedTypeAnnotation.err (+6 -0)
📝 pkl-parser/src/main/java/org/pkl/parser/Parser.java (+3 -0)
📝 pkl-parser/src/test/kotlin/org/pkl/parser/ParserComparisonTest.kt (+1 -0)

📄 Description

When a parethesized type atom is empty, an unexpected error occurs (due to an IndexOutOfBoundsException)

For example take t.pkl as a reproducible example:

class Bird { name: String }

bird1: String|Bird = "Pigeon"
bird2: String|()|Bird = new Bird { name = "Pigeon" }

Unexpected behavior: an unspecified error message is shown without source information:

$ pkl eval -f yaml t.pkl
An unexpected error has occurred. Would you mind filing a bug report?

Expected behavior: the parser gracefully throws an error that provides details of the error in the source file.

This PR addresses this issue by first checking if the children array is empty, and if it is, throwing a parser error when it is empty.

After applying the fix proposed here, the expected behavior occurs:

$ pkl eval -f yaml t.pkl
–– Pkl Error ––
Unexpected token `)`. Expected a type.

4 | bird2: String|()|Bird = new Bird { name = "Pigeon" }
                   ^
at t (file:///Users/spencer/scratch/pkl/t.pkl, line 4)

_{🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.}

## 📋 Pull Request Information **Original PR:** https://github.com/apple/pkl/pull/1323 **Author:** [@spyoungtech](https://github.com/spyoungtech) **Created:** 11/18/2025 **Status:** ✅ Merged **Merged:** 11/18/2025 **Merged by:** [@stackoverflow](https://github.com/stackoverflow) **Base:** `main` ← **Head:** `fix-empty-parethesized-type-error` --- ### 📝 Commits (4) - [`3c635a6`](https://github.com/apple/pkl/commit/3c635a60cefc151baeb8bf4d100c35d29e213c78) throw detailed error when parenthesized type is empty - [`6c69fa6`](https://github.com/apple/pkl/commit/6c69fa681d3949c3736f33e3c4a319f46f2e32ea) add test for empty parenthesized type annotation - [`5e45514`](https://github.com/apple/pkl/commit/5e45514fdb244399a7d3ca3544918a60054850f6) add new test to exceptions - [`5dde0e5`](https://github.com/apple/pkl/commit/5dde0e59215822322662ffa4c9991d9fb23da4ef) pass error location instead of backtracking ### 📊 Changes **4 files changed** (+11 additions, -0 deletions) <details> <summary>View changed files</summary> ➕ `pkl-core/src/test/files/LanguageSnippetTests/input/errors/emptyParenthesizedTypeAnnotation.pkl` (+1 -0) ➕ `pkl-core/src/test/files/LanguageSnippetTests/output/errors/emptyParenthesizedTypeAnnotation.err` (+6 -0) 📝 `pkl-parser/src/main/java/org/pkl/parser/Parser.java` (+3 -0) 📝 `pkl-parser/src/test/kotlin/org/pkl/parser/ParserComparisonTest.kt` (+1 -0) </details> ### 📄 Description When a parethesized type atom is empty, an unexpected error occurs (due to an `IndexOutOfBoundsException`) For example take `t.pkl` as a reproducible example: ```pkl class Bird { name: String } bird1: String|Bird = "Pigeon" bird2: String|()|Bird = new Bird { name = "Pigeon" } ``` **Unexpected behavior:** an unspecified error message is shown without source information: ``` $ pkl eval -f yaml t.pkl An unexpected error has occurred. Would you mind filing a bug report? ``` **Expected behavior:** the parser gracefully throws an error that provides details of the error in the source file. This PR addresses this issue by first checking if the `children` array is empty, and if it is, throwing a parser error when it is empty. After applying the fix proposed here, the expected behavior occurs: ``` $ pkl eval -f yaml t.pkl –– Pkl Error –– Unexpected token `)`. Expected a type. 4 | bird2: String|()|Bird = new Bird { name = "Pigeon" } ^ at t (file:///Users/spencer/scratch/pkl/t.pkl, line 4) ``` --- <sub>🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.</sub>

adam added the pull-request label 2025-12-30 01:28:19 +01:00

adam closed this issue

2025-12-30 01:28:19 +01:00

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Reference: starred/pkl#1018