feat(rendering): minify rendered HTML behind FEATURE_FLAG_MINIFY_HTML

[fmontes]

Claude finished @fmontes's task in 1m 58s —— View job

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Code Review — native HTML minification

• Gather context
• Review HtmlMinifier.java
• Review integration seams (VelocityLiveMode, VelocityModeHandler)
• Review FeatureFlagName + tests
• Post findings

Nice work — the design (two seams, cache-fill-time minification, best-effort fallback, idempotency, preserved regions) is sound and well-documented. One real correctness bug stands out.

New Issues

• 🟠 High: dotCMS/src/main/java/com/dotcms/rendering/util/HtmlMinifier.java:80-142 — Whitespace inside quoted attribute values is collapsed. minify() tracks no tag/attribute context; isSignificantBefore/isSignificantAfter only look at the immediately adjacent characters. Any whitespace run whose neighbors are not >/< is treated as significant inter-element text and collapsed to a single space — including whitespace inside an attribute value.

  Trace <input value="a b">: the a b run is preceded by a (≠ >, significant) and followed by b (≠ <, significant) → emitted as a b. Output becomes <input value="a b">.

  Impact when the flag is on:

  • <input type="hidden" value="two spaces"> → submitted form value silently changes.
  • data-config='{"key": "a b"}' and other JSON/data payloads → value changes, can break client JS.
  • alt/title/aria-label with intentional spacing → altered.
  • A newline inside an attribute value (VTL can emit these) is collapsed the same way.

  This is silent data corruption, not just cosmetic. The existing test test_minify_collapses_attribute_and_document_whitespace only covers whitespace between attributes (<div class="a" id="b">), so the case is untested. A minimal fix is to track whether the cursor is inside a tag and inside a quoted value, and copy attribute-value whitespace verbatim (and add a regression test).

  Fix this →

Notes (non-blocking)

• HtmlMinifier.java:253-266 — the while loop in findPreserveTagEnd always returns on its first iteration (the trailing return html.length() after the loop is unreachable). Not a bug, but the loop reads as if it iterates over multiple close-tag candidates when it does not. Consider replacing with a straight-line lookup for clarity.
• VelocityModeHandler.eval():111-113 — CSP-then-minify ordering is correct, and applying the minifier to preview/edit output is harmless. Good.
• LIVE path (VelocityLiveMode.writePage:265-280) correctly minifies before the cache add(), so the cost is paid per cache fill, and the non-minify branch still streams directly. Good.

Everything else — feature-flag gating, Config.getBooleanProperty, Logger.warnAndDebug on failure returning original markup, preserved-region handling, conditional-comment retention — follows dotCMS conventions and looks correct.

• branch issue-36851-native-html-minification

[claude]

Claude finished @fmontes's task in 1m 58s —— View job

---

Code Review — native HTML minification

• Gather context
• Review HtmlMinifier.java
• Review integration seams (VelocityLiveMode, VelocityModeHandler)
• Review FeatureFlagName + tests
• Post findings

Nice work — the design (two seams, cache-fill-time minification, best-effort fallback, idempotency, preserved regions) is sound and well-documented. One real correctness bug stands out.

New Issues

• 🟠 High: dotCMS/src/main/java/com/dotcms/rendering/util/HtmlMinifier.java:80-142 — Whitespace inside quoted attribute values is collapsed. minify() tracks no tag/attribute context; isSignificantBefore/isSignificantAfter only look at the immediately adjacent characters. Any whitespace run whose neighbors are not >/< is treated as significant inter-element text and collapsed to a single space — including whitespace inside an attribute value.

  Trace <input value="a b">: the a b run is preceded by a (≠ >, significant) and followed by b (≠ <, significant) → emitted as a b. Output becomes <input value="a b">.

  Impact when the flag is on:

  • <input type="hidden" value="two spaces"> → submitted form value silently changes.
  • data-config='{"key": "a b"}' and other JSON/data payloads → value changes, can break client JS.
  • alt/title/aria-label with intentional spacing → altered.
  • A newline inside an attribute value (VTL can emit these) is collapsed the same way.

  This is silent data corruption, not just cosmetic. The existing test test_minify_collapses_attribute_and_document_whitespace only covers whitespace between attributes (<div class="a" id="b">), so the case is untested. A minimal fix is to track whether the cursor is inside a tag and inside a quoted value, and copy attribute-value whitespace verbatim (and add a regression test).

  Fix this →

Notes (non-blocking)

• HtmlMinifier.java:253-266 — the while loop in findPreserveTagEnd always returns on its first iteration (the trailing return html.length() after the loop is unreachable). Not a bug, but the loop reads as if it iterates over multiple close-tag candidates when it does not. Consider replacing with a straight-line lookup for clarity.
• VelocityModeHandler.eval():111-113 — CSP-then-minify ordering is correct, and applying the minifier to preview/edit output is harmless. Good.
• LIVE path (VelocityLiveMode.writePage:265-280) correctly minifies before the cache add(), so the cost is paid per cache fill, and the non-minify branch still streams directly. Good.

Everything else — feature-flag gating, Config.getBooleanProperty, Logger.warnAndDebug on failure returning original markup, preserved-region handling, conditional-comment retention — follows dotCMS conventions and looks correct.

• branch issue-36851-native-html-minification

[Copilot]

Pull request overview

Adds a feature-flagged, dependency-free HTML minification step to dotCMS’s rendering pipeline so rendered pages can be served (and, in LIVE mode, cached) without indentation/blank lines/comments introduced by Velocity templates—opt-in via FEATURE_FLAG_MINIFY_HTML.

Changes:

• Introduces HtmlMinifier to conservatively collapse insignificant whitespace and strip HTML comments while preserving <pre>, <textarea>, <script>, and <style> bodies.
• Hooks minification into VelocityLiveMode.writePage() (before page cache write) and into VelocityModeHandler.eval() (post-CSP processing path).
• Adds FEATURE_FLAG_MINIFY_HTML and a new unit test suite for the minifier.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
dotCMS/src/main/java/com/dotcms/rendering/util/HtmlMinifier.java	New minifier implementation guarded by FEATURE_FLAG_MINIFY_HTML.
dotCMS/src/main/java/com/dotcms/rendering/velocity/servlet/VelocityLiveMode.java	Minifies LIVE mode output before writing/storing into the page cache when enabled.
dotCMS/src/main/java/com/dotcms/rendering/velocity/servlet/VelocityModeHandler.java	Minifies eval() output (after CSP application when configured).
dotCMS/src/main/java/com/dotcms/featureflag/FeatureFlagName.java	Adds the FEATURE_FLAG_MINIFY_HTML feature flag constant + javadoc.
dotCMS/src/test/java/com/dotcms/rendering/util/HtmlMinifierTest.java	Adds unit tests for whitespace significance, preserved regions, comments, and idempotence.