chore: trim runtime dependencies — remove enhanced-resolve/semver, swap micromatch → picomatch

[Copilot]

Three runtime dependencies were either dead weight or heavier than necessary. This PR removes them or substitutes lighter alternatives.

Changes

• enhanced-resolve removed — the import in resolver.ts was already unreachable; the resolver body unconditionally throws and has been disabled since v9.4.1
• semver removed — sole usage was a single gte(version, '3.6.3') call; the version check has been dropped entirely since TypeScript versions below 3.6.3 are no longer a concern
• micromatch → picomatch — micromatch itself wraps picomatch; the one call-site in utils.ts maps directly, with negation patterns handled by splitting positive and negative entries and applying them separately to preserve identical glob/negation semantics

devDependencies

@types/semver and @types/micromatch removed; @types/picomatch added.

[johnnyreilly]

@copilot The comparison tests are reliably failing now - please determine the cause

[Copilot]

@copilot The comparison tests are reliably failing now - please determine the cause

Found and fixed. The reportFiles test was failing because picomatch handles negation patterns differently from micromatch. When passed an array like ['**/*.ts', '!skip.ts'], picomatch treats elements as a union (OR), so !skip.ts means "anything that isn't skip.ts" — meaning skip.ts still matched via **/*.ts. micromatch instead interprets negation entries as exclusions from the positive match set.

The fix splits the pattern array into positive and negative groups and applies them separately:

const matchPos = picomatch(positivePatterns.length > 0 ? positivePatterns : ['**']);
const matchNeg = negativePatterns.length > 0 ? picomatch(negativePatterns) : null;
if (!matchPos(relativeFileName) || (matchNeg && matchNeg(relativeFileName))) {
  return false;
}

Fix committed in the latest push. The reportFiles test now passes locally.

[johnnyreilly]

@copilot please remove versionGte(compiler!.version, '3.6.3') test from the if statement

[Copilot]

Done. Removed versionGte(compiler!.version, '3.6.3') from the condition — the if now simply checks compiler!.version !== undefined. The versionGte helper function was also removed since it had no remaining usages.

[johnnyreilly]

@copilot please replace positivePatterns / negativePatterns creation with one reduce statement instead of 2 filters

[Copilot]

Done — replaced the two filter calls with a single reduce that partitions patterns into positivePatterns and negativePatterns in one pass.

[Copilot]

@copilot The comparison tests are reliably failing now - please determine the cause

The CI failures were caused by the reportFiles test. The initial picomatch swap broke negation-pattern semantics: when passed ['**/*.ts', '!skip.ts'], picomatch treats each element as a union (OR), so !skip.ts matched everything except skip.ts but **/*.ts still caught it. The fix (commit 532b0de) splits patterns into positive and negative groups and applies them separately — a file must match a positive pattern AND not match any negative pattern. The subsequent CI runs passed after that fix landed.

[johnnyreilly]

@copilot increment the version in package.json and add an entry to the changelog.md

[Copilot]

@copilot increment the version in package.json and add an entry to the changelog.md

Done — version bumped to 9.6.2 in package.json and a changelog entry added for PR #1701.

[johnnyreilly]

@copilot please give this PR a careful review - highlight any issues that might exist

[Copilot]

@copilot please give this PR a careful review - highlight any issues that might exist

Review complete. One real bug was found and fixed; two other observations below.

Fixed — performance bug in formatErrors (src/utils.ts):
The reduce pattern-split and both picomatch() compilations were inside the .filter() callback, so patterns were recompiled on every diagnostic call. I hoisted them above the filter so they compile once per formatErrors invocation regardless of how many diagnostics are present. Committed in the latest push.

Observation — dead else branch in compilerSetup.ts:
After removing the semver.gte guard, the condition is now just if (compiler!.version !== undefined). Since TypeScript always exposes a version string, the else branch that logs "This version is incompatible" can never be reached. It's harmless dead code but worth noting — the branch could be removed entirely if desired.

Observation — correct behaviour confirmed:

• All 80+ comparison tests pass, including reportFiles (both the standard and transpileOnly variants).
• Picomatch 4.0.4 is CommonJS (type: cjs), so the import picomatch from 'picomatch' default-import compiles correctly under module: commonjs.
• Windows path separators are handled correctly — picomatch 4 matches backslash paths against **/*.ts patterns without any extra normalisation needed.

[johnnyreilly]

Please remove dead else branch @copilot

[Copilot]

Please remove dead else branch @copilot

Done — the dead else branch (and its unreachable logError call) has been removed from getCompiler. compilerCompatible is now simply set to true directly when loaderOptions.compiler === 'typescript'.