Integrate @ohm-js/wasm for faster parsing by charlespwd · Pull Request #1116 · Shopify/theme-tools

charlespwd · 2026-02-03T18:31:35Z

Summary

Faster Liquid parsing via WebAssembly by integrating @ohm-js/wasm (v0.6.17) in place of ohm-js package.

Key Changes

ohm-wasm integration: Replaced ohm-js with @ohm-js/wasm for better perforamnce
Test expectation updates: Updated CST snapshots to reflect ohm-wasm output format

Technical Notes

This implementation uses v0.6.17 API patterns:

Closure-based toAst: Captures Ohm reference via closure instead of global access
ifPresent for OptNode: Handles optional nodes cleanly (e.g., node.ifPresent(n => n.toAst(Ohm)))
Deferred children pattern: Uses () => children.map(...) for lazy AST construction

Performance

before	after

About 3s faster on theme-check vs dawn.

Note

This builds on top of the browser test infrastructure added in PR #1112 and #1113 and @pdubroy in #1070

charlespwd · 2026-02-03T19:49:45Z

Integrate @ohm-js/wasm for faster parsing #1116 👈 (View in Graphite)
Upgrade Prettier to v3 #1118
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This stack of pull requests is managed by Graphite. Learn more about stacking.

Key changes: - Add @ohm-js/wasm dependency - Update imports to use @ohm-js/wasm and @ohm-js/wasm/compat Co-Authored-By: Patrick Dubroy <pdubroy@gmail.com> Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

@ohm-js/wasm v0.6.17 FailedMatchResult returns generic "Match failed at pos N" messages instead of detailed syntax error information. getExpectedText() is not yet implemented in the WASM version. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

charlespwd · 2026-02-04T14:01:21Z

.github/workflows/ci.yml

      matrix:
        os: [windows-latest, ubuntu-latest]
-        node-version: [18, 20]
+        node-version: [20]


Had to drop node 18 support (dead) because of ESM support in 20+.

charlespwd · 2026-02-04T14:27:41Z

packages/theme-check-common/src/checks/liquid-html-syntax-error/index.spec.ts

    expect(offenses).to.have.length(1);
-    expect(offenses[0].message).to.equal(`SyntaxError: expected ">", not """`);
+    // Note: @ohm-js/wasm returns generic error messages; getExpectedText() is not implemented
+    expect(offenses[0].message).to.equal(`Match failed at pos 21`);


That diff is probably the only reason we can't merge this right now. Match failed at pos 21 won't make any sense to an end user.

This has been resolved in the latest published version (0.7.5).

pdubroy

Thanks, this helped me recognize a number of issues that I still had. They're mostly fixed now.

Error messages

Error messages are now consistent with the JS version, although the order may differ: e.g., the Wasm version can say "c", "b", or "a" where the JS version says "a", "b", or "c". Let me know if you think that will be a problem.

I tried reverting your commit that changed the expectations for error messages — they all pass now, except for two. One is just an ordering issue. For the other one, it looks like you have some code which reformats the original Ohm error, and the regex isn't correctly parsing the Ohm message, so some information gets dropped. (Ohm's original error message in the Wasm version is equal to the JS version, modulo ordering.)

`using`

Even though I intended to support the using keyword (in addition to the use() method for environments that don't yet support using), there was an issue with my implementation. It looks like Claude tried to work around that with the whole "deferred children" mechanism. I've fixed the issue, so we shouldn't need any of that anymore.

`process`

Fixed up the usage so Webpack should no longer complain.

pdubroy · 2026-02-09T11:05:31Z

packages/liquid-html-parser/package.json

    "type-check": "tsc --noEmit"
  },
  "dependencies": {
+    "@ohm-js/wasm": "^0.6.17",


Suggested change

"@ohm-js/wasm": "^0.6.17",

"@ohm-js/wasm": "^0.7.5",

pdubroy · 2026-02-09T11:06:02Z

packages/theme-check-common/src/checks/liquid-html-syntax-error/index.spec.ts

    expect(offenses).to.have.length(1);
-    expect(offenses[0].message).to.equal(`SyntaxError: expected ">", not """`);
+    // Note: @ohm-js/wasm returns generic error messages; getExpectedText() is not implemented
+    expect(offenses[0].message).to.equal(`Match failed at pos 21`);


This has been resolved in the latest published version (0.7.5).

pdubroy · 2026-02-09T15:38:41Z

packages/vscode-extension/webpack.config.js

+      // @ohm-js/wasm checks this at runtime; define it to avoid "process is not defined" errors
+      'process.env.OHM_DEBUG': JSON.stringify(false),


Suggested change

// @ohm-js/wasm checks this at runtime; define it to avoid "process is not defined" errors

'process.env.OHM_DEBUG': JSON.stringify(false),

Should be fixed in 0.7.5.

pdubroy · 2026-02-09T15:38:56Z

packages/vscode-extension/webpack.config.js

+      // @ohm-js/wasm checks this at runtime; define it to avoid "process is not defined" errors
+      'process.env.OHM_DEBUG': JSON.stringify(false),


Suggested change

// @ohm-js/wasm checks this at runtime; define it to avoid "process is not defined" errors

'process.env.OHM_DEBUG': JSON.stringify(false),

pdubroy · 2026-02-09T15:39:12Z

packages/vscode-extension/webpack.config.js

+        // @ohm-js/wasm checks this at runtime; define it to avoid "process is not defined" errors
+        'process.env.OHM_DEBUG': JSON.stringify(false),


Suggested change

// @ohm-js/wasm checks this at runtime; define it to avoid "process is not defined" errors

'process.env.OHM_DEBUG': JSON.stringify(false),

pdubroy · 2026-02-09T15:39:22Z

packages/vscode-extension/webpack.test.config.js

+      // @ohm-js/wasm checks this at runtime; define it to avoid "process is not defined" errors
+      'process.env.OHM_DEBUG': JSON.stringify(false),


Suggested change

// @ohm-js/wasm checks this at runtime; define it to avoid "process is not defined" errors

'process.env.OHM_DEBUG': JSON.stringify(false),

charlespwd force-pushed the cp-ohm-wasm-v2 branch from 4062f5e to e94e43a Compare February 3, 2026 19:43

charlespwd changed the base branch from main to graphite-base/1116 February 3, 2026 19:49

charlespwd changed the base branch from graphite-base/1116 to cp-prettier-v3 February 3, 2026 19:49

charlespwd mentioned this pull request Feb 3, 2026

Upgrade Prettier to v3 #1118

Merged

1 task

charlespwd force-pushed the cp-ohm-wasm-v2 branch from e94e43a to a4a380d Compare February 3, 2026 19:55

charlespwd force-pushed the cp-prettier-v3 branch 2 times, most recently from a2058e7 to 8c981ca Compare February 3, 2026 20:03

charlespwd force-pushed the cp-ohm-wasm-v2 branch 3 times, most recently from c5a9f07 to 3245c58 Compare February 3, 2026 20:10

Base automatically changed from cp-prettier-v3 to main February 4, 2026 14:00

charlespwd and others added 2 commits February 4, 2026 09:00

Integrate @ohm-js/wasm for faster parsing

9089e92

Key changes: - Add @ohm-js/wasm dependency - Update imports to use @ohm-js/wasm and @ohm-js/wasm/compat Co-Authored-By: Patrick Dubroy <pdubroy@gmail.com> Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

charlespwd force-pushed the cp-ohm-wasm-v2 branch from 3245c58 to efa1715 Compare February 4, 2026 14:00

charlespwd commented Feb 4, 2026

View reviewed changes

charlespwd changed the title ~~Integrate @ohm-js/wasm for browser-compatible parsing~~ Integrate @ohm-js/wasm for faster parsing Feb 4, 2026

pdubroy reviewed Feb 9, 2026

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Integrate @ohm-js/wasm for faster parsing#1116

Integrate @ohm-js/wasm for faster parsing#1116
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cp-ohm-wasm-v2

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		// @ohm-js/wasm checks this at runtime; define it to avoid "process is not defined" errors
		'process.env.OHM_DEBUG': JSON.stringify(false),

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Summary

Key Changes

Technical Notes

Performance

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charlespwd commented Feb 3, 2026 •

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`using`

`process`