Compare Tabs

Adds file comparison to the editor tab context menu, plus a Paste Compare panel for diffing two pasted texts — with the formatting and normalisation that makes such a diff readable in the first place.

Features

1. Compare via tab context menu

• Right-click any editor tab → Select for Compare
• Right-click another tab → Compare with Selected to open the diff view
• Right-click any editor tab → Compare with Clipboard to diff that file against the clipboard
• Select two files in the Explorer → Compare 2 Selected Files

("Compare with Selected" only appears after a tab has been selected, matching the built-in Explorer behavior. If the selected file has since been deleted, you are told rather than shown a broken diff.)

2. Paste Compare

Click ⇆ Paste Compare in the status bar (or press Cmd/Ctrl+Alt+Shift+D) — an empty editable diff opens immediately. Paste one text into the left side, the other into the right; differences highlight live as you type.

The diff is backed by an in-memory file system (paste-compare: scheme): edits auto-save back to memory — no save prompts, no temp files on disk, no stray Untitled tabs. Opening the panel again starts a new session rather than wiping the compare you are in the middle of.

Language is auto-detected from the pasted text and applied to both sides for syntax highlighting (JSON, JSONC, YAML, XML, HTML, PHP, SQL, Python, Shell, Dockerfile, diff, C/C++, Java, Go, Rust, TypeScript, JavaScript, CSS, Markdown, INI/TOML, .properties). Click the language in the status bar to override it.

Line counts (+12 −7) sit next to it. They are computed with Myers' algorithm, the same one git diff uses; a ~ prefix means the two sides differ too much for an exact line diff, so the counts are an order-insensitive estimate.

3. Normalisation — the $(tools) button in the diff toolbar

Two minified JSON blobs diff into one unreadable line. These fix that:

Every operation is applied as a workspace edit, so plain undo steps back through it. Restore Text as Pasted is the coarser escape hatch: one jump back to the text as pasted.

Mask Noise

Two log lines that differ only in their timestamp are not worth diffing. Masking replaces volatile values with a constant placeholder so the lines that genuinely differ stand out:

2026-09-14T10:23:11.123Z [req 550e8400-e29b-41d4-a716-446655440000] 412ms 10.0.0.7:8080
                                    ↓
<TS> [req <UUID>] <DUR> <IP>

The picker pre-ticks only the masks that actually match the text in front of you and shows each one's hit count, so the usual case is one Enter. Presets cover ISO timestamps, clock times, UUIDs, epoch milliseconds, hex ids and hashes, durations, IP addresses, stack-trace line:column and plain numbers.

For the request ids and thread names specific to your own logs, add your own in compareTabs.maskPatterns:

"compareTabs.maskPatterns": [
  { "pattern": "trace-[0-9a-f]{16}", "replacement": "<TRACE>", "label": "Trace id" },
  { "pattern": "pool-\\d+-thread-\\d+", "replacement": "<THREAD>", "label": "Thread" }
]

On regex safety. A pattern that repeats a group which itself repeats — (a+)+, (\d+\.)+ — is rejected before it runs. JavaScript cannot time-bound a regular expression in-process: by the time you could measure that one is slow it has already frozen the editor, with no way to interrupt it. Refusing the dangerous shape up front is the only defence that runs before the damage, so the check is deliberately conservative — a few safe patterns get rejected too, and you get a message saying which and why.

4. Getting text in

• Send Selection to Paste Compare — right-click a selection in any editor. The first invocation fills the left side, the next fills the right.
• Load Side from File… and Paste Clipboard into Side
• Save Focused Side As… — writes the side you are in to a real file, with an extension suggested by the detected language.

Settings

Languages

The UI ships in English and 简体中文, following the VS Code display language.

Development

npm test              # unit tests — no install needed, node builtins only
npm install           # optional: @types/vscode, for IntelliSense in the editor

Press F5 to launch an Extension Development Host.

The three leaf modules deliberately avoid importing vscode, so they run — and are tested — under plain node.

Packaging & Installing

npm run package                      # produces a .vsix
code --install-extension compare-tabs-0.1.1.vsix

Related built-in features (no extension needed)

• Compare Active File with Clipboard — current file vs clipboard
• Compare New Untitled Text Files — two blank editors to paste into manually