fix: replace unsupported lookahead regex in create-github-release.rs

.codacy.yml

@@ -4,3 +4,4 @@ exclude_paths:
   - "ci-logs/**"
   - "changelog.d/**"
   - "scripts/**"
+  - "experiments/**"

changelog.d/20260322_112614_fix_regex_lookahead_create_github_release.md

@@ -0,0 +1,7 @@
+---
+bump: patch
+---
+
+### Fixed
+
+- Fixed panic in `scripts/create-github-release.rs` caused by unsupported regex lookahead assertion `(?=...)` in Rust's `regex` crate, which prevented GitHub release creation for v0.3.0

docs/case-studies/issue-137/README.md

@@ -0,0 +1,190 @@
+# Case Study: Issue #137 — GitHub Release Failed (v0.3.0)
+
+## Overview
+
+- **Issue:** [#137](https://github.com/linksplatform/Numbers/issues/137)
+- **Failing Run:** [23400025602](https://github.com/linksplatform/Numbers/actions/runs/23400025602)
+- **Date:** 2026-03-22
+- **Status:** Root cause identified and fixed in PR [#138](https://github.com/linksplatform/Numbers/pull/138).
+- **Symptom:** Git tag `v0.3.0` was created and crate was published to crates.io, but the GitHub release object was never created. The version in `Cargo.toml` (`0.3.0`) and the GitHub "Latest" release (`v0.2.1`) are out of sync.
+
+---
+
+## Timeline / Sequence of Events
+
+1. **2026-03-22 ~08:08 UTC** — PR #136 merged, fixing CI/CD failures from issue #135.
+2. **2026-03-22 ~09:23 UTC** — Push to `main` triggers the "Auto Release" job in the Rust CI/CD pipeline.
+3. **09:23–09:24 UTC** — All preceding steps succeed:
+   - Detect Changes ✓
+   - Lint and Format Check ✓
+   - Tests (ubuntu, windows, macOS) ✓
+   - Code Coverage ✓
+   - Build Package ✓
+   - Changelog collected and processed ✓
+   - Version bumped from `0.2.x` → `0.3.0` ✓
+   - `v0.3.0` Git tag created ✓
+   - Crate published to crates.io ✓
+4. **09:25:08 UTC** — "Create GitHub Release" step **PANICS** with exit code 101.
+5. **Result:** GitHub release `v0.3.0` never created. GitHub shows `v0.2.1` as the latest release.
+
+---
+
+## Root Cause Analysis
+
+### The Failing Step
+
+The CI workflow runs (see `rust.yml`, "Create GitHub Release" step):
+
+```bash
+rust-script scripts/create-github-release.rs \
+  --release-version "${{ steps.current_version.outputs.version }}" \
+  --repository "${{ github.repository }}"
+```
+
+### Exact Error (from CI log `run-23400025602.log`)
+
+```
+2026-03-22T09:25:08.6365777Z Creating GitHub release for v0.3.0...
+2026-03-22T09:25:08.6367525Z thread 'main' (5089) panicked at
+    /home/runner/work/Numbers/Numbers/scripts/create-github-release.rs:47:35:
+2026-03-22T09:25:08.6374178Z regex parse error:
+    (?s)## \[0\.3\.0\].*?\n(.*?)(?=\n## \[|$)
+2026-03-22T09:25:08.6374987Z error: look-around, including look-ahead and look-behind, is not supported
+2026-03-22T09:25:08.6384819Z ##[error]Process completed with exit code 101.
+```
+
+### Buggy Code
+
+In `scripts/create-github-release.rs`, lines 45–47:
+
+```rust
+let escaped_version = regex::escape(version);
+let pattern = format!(r"(?s)## \[{}\].*?\n(.*?)(?=\n## \[|$)", escaped_version);
+let re = Regex::new(&pattern).unwrap();
+```
+
+The pattern uses a **positive lookahead assertion** `(?=\n## \[|$)` to locate the end of a changelog section without consuming the next section's header.
+
+### Why This Fails
+
+Rust's [`regex`](https://docs.rs/regex) crate deliberately **does not support look-around** (lookahead or lookbehind). This is an explicit design decision: the crate guarantees linear-time matching by restricting the regex engine to finite-state automata. Lookaheads require backtracking and are incompatible with this guarantee.
+
+From the [`regex` crate documentation](https://docs.rs/regex/latest/regex/#syntax):
+
+> Look-around, including look-ahead and look-behind, is not supported.
+
+The script compiled successfully during development only if it was tested with a regex that didn't trigger the `.unwrap()` panic (e.g., the pattern was never exercised, or it was developed/tested with a different regex engine such as the `fancy-regex` crate).
+
+### Why It Wasn't Caught Earlier
+
+1. **No unit tests for `create-github-release.rs`** — The script was never run against a real CHANGELOG.md in a test environment before the first actual release.
+2. **`Regex::new(...).unwrap()` panics at runtime** — The regex is compiled at runtime, not compile time. No compile-time error occurs.
+3. **The script is only exercised during an actual release** — It's not invoked during PRs, lint, or test jobs. The first time it ran was the v0.3.0 release attempt.
+
+---
+
+## Fix
+
+Replace the unsupported lookahead `(?=\n## \[|$)` with a standard non-capturing group `(?:\n## \[|$)`.
+
+**Before (broken):**
+```rust
+let pattern = format!(r"(?s)## \[{}\].*?\n(.*?)(?=\n## \[|$)", escaped_version);
+```
+
+**After (fixed):**
+```rust
+// Use a pattern without lookahead (not supported by the `regex` crate).
+// Match the section header and capture everything until the next section or end of string.
+let pattern = format!(r"(?s)## \[{}\][^\n]*\n(.*?)(?:\n## \[|$)", escaped_version);
+```
+
+**Changes:**
+1. `.*?` after the version header → `[^\n]*` (more precisely matches the rest of the header line, e.g., ` - 2026-03-22`).
+2. `(?=\n## \[|$)` (lookahead) → `(?:\n## \[|$)` (non-capturing group).
+
+The non-capturing group consumes the `\n## [` delimiter, but since the captured group `(.*?)` stops before it and `.trim()` is called on the result, the release notes body is still extracted correctly.
+
+**Verified via experiment** (`experiments/test-changelog-regex.rs`):
+- v0.3.0 section extracted correctly, not including v0.2.1 content ✓
+- v0.2.1 section extracted correctly, not including v0.3.0 content ✓
+- Missing version returns fallback `"Release v9.9.9"` ✓
+
+---
+
+## Workaround
+
+Since the v0.3.0 Git tag and crates.io publication already succeeded, the GitHub release was created manually:
+
+```bash
+gh release create v0.3.0 \
+  --repo linksplatform/Numbers \
+  --title "v0.3.0" \
+  --notes "$(sed -n '/^## \[0\.3\.0\]/,/^## \[/{ /^## \[0\.3\.0\]/d; /^## \[/d; p }' CHANGELOG.md)"
+```
+
+---
+
+## Possible Solutions (Research)
+
+### Option 1: Fix the regex pattern (implemented)
+
+Replace lookahead with a non-capturing group (as done in this fix). Minimal change, no new dependencies.
+
+### Option 2: Use `fancy-regex` crate
+
+The [`fancy-regex`](https://crates.io/crates/fancy-regex) crate is a drop-in superset of the `regex` crate that supports lookaheads and lookbehinds at the cost of potentially exponential worst-case time.
+
+```toml
+[dependencies]
+fancy-regex = "0.13"
+```
+
+```rust
+use fancy_regex::Regex;
+let pattern = format!(r"(?s)## \[{}\].*?\n(.*?)(?=\n## \[|$)", escaped_version);
+```
+
+This would allow using the original pattern without change, but adds a new dependency.
+
+### Option 3: Parse changelog without regex
+
+Split the changelog content by `\n## [` and find the matching section by prefix. This is simpler and avoids any regex pitfalls:
+
+```rust
+fn get_changelog_for_version(content: &str, version: &str) -> String {
+    let header = format!("## [{}]", version);
+    let sections: Vec<&str> = content.split("\n## [").collect();
+    for section in &sections {
+        if section.starts_with(&header[3..]) { // skip leading "## "
+            return section
+                .splitn(2, '\n')
+                .nth(1)
+                .unwrap_or("")
+                .trim()
+                .to_string();
+        }
+    }
+    format!("Release v{}", version)
+}
+```
+
+### Option 4: Use existing tooling (`git-cliff`, `github-changelog-generator`, etc.)
+
+Projects like [`git-cliff`](https://github.com/orhun/git-cliff) and [`release-plz`](https://github.com/MarcoIeni/release-plz) provide battle-tested changelog and release management. Adopting such a tool would replace custom scripts with maintained community solutions.
+
+---
+
+## Related Issues
+
+- [#135](https://github.com/linksplatform/Numbers/issues/135) — Previous CI/CD failures (unused import, Mono not found) — fixed in PR #136
+- [#127](https://github.com/linksplatform/Numbers/issues/127) — Missing `cargo publish` step — fixed in PR #128
+- [#132](https://github.com/linksplatform/Numbers/issues/132) — Migration of CI/CD scripts to Rust — fixed in PR #133
+
+---
+
+## Artifacts
+
+- **CI Logs:** [`ci-logs/run-23400025602.log`](ci-logs/run-23400025602.log)
+- **Experiment Script:** [`../../experiments/test-changelog-regex.rs`](../../experiments/test-changelog-regex.rs)
+- **Fixed Script:** [`../../scripts/create-github-release.rs`](../../scripts/create-github-release.rs)

experiments/test-changelog-regex.rs

@@ -0,0 +1,68 @@
+#!/usr/bin/env rust-script
+//! Test the fixed changelog regex pattern
+//!
+//! ```cargo
+//! [dependencies]
+//! regex = "1"
+//! ```
+
+use regex::Regex;
+
+fn get_changelog_for_version(content: &str, version: &str) -> String {
+    let escaped_version = regex::escape(version);
+    let pattern = format!(r"(?s)## \[{}\][^\n]*\n(.*?)(?:\n## \[|$)", escaped_version);
+    let re = Regex::new(&pattern).unwrap();
+
+    if let Some(caps) = re.captures(content) {
+        caps.get(1).unwrap().as_str().trim().to_string()
+    } else {
+        format!("Release v{}", version)
+    }
+}
+
+fn main() {
+    let changelog = r#"# Changelog
+
+## [0.3.0] - 2026-03-22
+
+### Added
+- Feature A
+- Feature B
+
+### Fixed
+- Bug C
+
+## [0.2.1] - 2025-12-28
+
+### Fixed
+- Bug D
+
+## [0.2.0] - 2025-11-01
+
+### Added
+- Initial release
+"#;
+
+    println!("=== Testing version 0.3.0 ===");
+    let result = get_changelog_for_version(changelog, "0.3.0");
+    println!("{}", result);
+    assert!(result.contains("Feature A"), "Should contain Feature A");
+    assert!(result.contains("Bug C"), "Should contain Bug C");
+    assert!(!result.contains("Bug D"), "Should NOT contain Bug D from 0.2.1");
+    println!("✓ PASS: 0.3.0 section parsed correctly");
+
+    println!("\n=== Testing version 0.2.1 ===");
+    let result = get_changelog_for_version(changelog, "0.2.1");
+    println!("{}", result);
+    assert!(result.contains("Bug D"), "Should contain Bug D");
+    assert!(!result.contains("Feature A"), "Should NOT contain Feature A from 0.3.0");
+    println!("✓ PASS: 0.2.1 section parsed correctly");
+
+    println!("\n=== Testing version not found ===");
+    let result = get_changelog_for_version(changelog, "9.9.9");
+    println!("{}", result);
+    assert_eq!(result, "Release v9.9.9");
+    println!("✓ PASS: fallback to 'Release v9.9.9' when version not found");
+
+    println!("\n=== All tests passed! ===");
+}

experiments/test-regex-fix.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+# Test that the fixed regex pattern correctly parses CHANGELOG.md sections
+
+# Simulate what the Rust code does - test the pattern
+CHANGELOG="/tmp/gh-issue-solver-1774178393929/CHANGELOG.md"
+VERSION="0.3.0"
+ESCAPED_VERSION=$(echo "$VERSION" | sed 's/\./\\./g')
+
+echo "=== Testing version: $VERSION ==="
+echo "=== Pattern: (?s)## \\[$ESCAPED_VERSION\\][^\\n]*\\n(.*?)(?:\\n## \\[|$) ==="
+
+# Check the regex crate doesn't support lookahead - that's confirmed
+# Our fix replaces (?=...) with non-capturing group (?:...)
+echo ""
+echo "Old pattern (broken): (?s)## \\[$ESCAPED_VERSION\\].*?\\n(.*?)(?=\\n## \\[|\$)"
+echo "New pattern (fixed):  (?s)## \\[$ESCAPED_VERSION\\][^\\n]*\\n(.*?)(?:\\n## \\[|\$)"
+echo ""
+echo "Key change: (?=\n## \[) is a LOOKAHEAD (not supported by Rust's regex crate)"
+echo "            (?:\n## \[) is a NON-CAPTURING GROUP (fully supported)"
+echo ""
+echo "The old (?=...) lookahead would preserve the '\n## [' prefix in the string."
+echo "The new (?:...) non-capturing group will consume it, but .trim() removes trailing whitespace"
+echo "and we capture content BEFORE the next section boundary anyway."

scripts/create-github-release.rs

@@ -43,7 +43,9 @@ fn get_changelog_for_version(version: &str) -> String {
     };
 
     let escaped_version = regex::escape(version);
-    let pattern = format!(r"(?s)## \[{}\].*?\n(.*?)(?=\n## \[|$)", escaped_version);
+    // Use a pattern without lookahead (not supported by the `regex` crate).
+    // Match the section header and capture everything until the next section or end of string.
+    let pattern = format!(r"(?s)## \[{}\][^\n]*\n(.*?)(?:\n## \[|$)", escaped_version);
     let re = Regex::new(&pattern).unwrap();
 
     if let Some(caps) = re.captures(&content) {