Error gracefully when encountering date values in TOML config files #11651

dario-piotrowicz · 2025-12-15T17:10:19Z

Note

Implemented by Claude Opus 4.5 🤖

Detect TOML Date values in vars configuration early and provide a helpful error message explaining that unquoted dates like DATE = 2024-01-01 are parsed as Date objects, and how to fix it by wrapping in quotes.

Tests
- Tests included/updated
- Tests not necessary because:
Public documentation
- Cloudflare docs PR(s):
- Documentation not necessary because: bugfix
Wrangler V3 Backport
- Wrangler PR: V3 Backport: fix: Automatically convert TOML Date values in vars to strings #11652
- Not necessary because:

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changeset-bot · 2025-12-15T17:10:23Z

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dario-piotrowicz · 2025-12-15T17:20:45Z

The changes in this PR have been authored by Claude, I've manually tested them and they do seem to do the trick:

ascorbic · 2025-12-15T17:33:07Z

Could we instead make it behave correctly? i.e. convert it back to a string when parsing?

dario-piotrowicz · 2025-12-15T17:49:36Z

Could we instead make it behave correctly? i.e. convert it back to a string when parsing?

good point 👍

github-actions · 2025-12-15T18:02:44Z

Failed to automatically backport this PR's changes to Wrangler v3. Please manually create a PR targeting the v3-maintenance branch with your changes. Thank you for helping us keep Wrangler v3 supported!

Depending on your changes, running git rebase --onto v3-maintenance main claude/7755 might be a good starting point.

Notes:

your PR branch should be named v3-backport-11651
add the skip-v3-pr label to the current PR to stop this workflow from failing

vicb · 2025-12-16T08:01:39Z

packages/workers-utils/src/config/validation.ts

+				for (const [varName, varValue] of Object.entries(value)) {
+					if (varValue instanceof Date) {
+						// Convert Date to ISO date string (YYYY-MM-DD format)
+						const dateString = varValue.toISOString().split("T")[0];


Is this correct to convert to "YYYY-MM-DD" ?

TOML supports multiple distinct date formats and we might end up with a string that is not what is in the TOML file.

At least we should have more tests and test the round trip transformation from the string in TOML to the string value of the var

ref: https://github.com/squirrelchat/smol-toml/blob/mistress/src/date.ts

The initial implementation is probably the right thing to do - there does not seem to be a way to get a original string value with the parsing lib we use

I'm pretty sure the real implementation creates smol-toml TomlDate objects which are Date subclasses. They can round-trip the string values. The problem is that the test is using JS Date objects. Really they should use parseToml to get the correct objects.

Even then const dateString = varValue.toISOString().split("T")[0]; might work by chance or be broken.

IIUC https://github.com/squirrelchat/smol-toml/blob/mistress/test/date.test.ts#L39 show that it doesn't roundtrip unchanged

I agree with @vicb here, I've been poking around and the raw data seems to indeed get lost.

And as Victor pointed out there doesn't seem to be a reliable way to covert back the date to a string that resembles the user's text, so I do think that just erroring is the right implementation here 🤔

vicb

I don't think this will work with i.e. lt1 = 07:32:00

TOML parses unquoted date values like DATE = 2024-01-01 as Date objects. Previously this caused a confusing error from Miniflare. Now wrangler automatically converts Date values to ISO date strings (YYYY-MM-DD format) and shows a warning suggesting to wrap the value in quotes. Co-authored-by: Dario Piotrowicz <[email protected]>

dario-piotrowicz · 2025-12-18T18:57:15Z

I don't think this will work with i.e. lt1 = 07:32:00

indeed that would not work at all, I do think that we should just error 👍

claude · 2025-12-18T19:19:35Z

Claude finished @dario-piotrowicz's task —— View job

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.changeset/floppy-tips-play.md (wrangler)

✅ Version type: patch (correct for a bug fix improvement)
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.changeset/tangy-knives-allow.md (@cloudflare/workers-utils)

✅ Version type: patch (correct for a bug fix improvement)
✅ Clear title and helpful description with example
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Both changesets properly describe the symptom being fixed (unhelpful error messages for TOML date values) and provide clear examples of the correct usage. The change is correctly categorized as a patch-level improvement across both affected packages.

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pkg-pr-new · 2025-12-18T19:25:18Z

create-cloudflare

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@cloudflare/kv-asset-handler

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miniflare

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@cloudflare/pages-shared

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@cloudflare/unenv-preset

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@cloudflare/vite-plugin

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@cloudflare/vitest-pool-workers

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@cloudflare/workers-editor-shared

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@cloudflare/workers-utils

npm i https://pkg.pr.new/@cloudflare/workers-utils@11651

wrangler

npm i https://pkg.pr.new/wrangler@11651

commit: 64f9f77

.changeset/floppy-tips-play.md

.changeset/tangy-knives-allow.md

Co-authored-by: Victor Berchet <[email protected]>

.changeset/tangy-knives-allow.md

vicb · 2025-12-19T12:28:51Z

packages/workers-utils/src/config/validation.ts

+					if (varValue instanceof Date) {
+						diagnostics.errors.push(
+							`The field "${fieldPath}.${varName}" is a TOML date, which is not supported. ` +
+								`Please use a string instead, e.g. ${varName} = "${varValue.toISOString().split("T")[0]}".`


${varName} = "${varValue.toISOString().split("T")[0]}

is not really helpful for times. Maybe only ask to quote the value?

The value here is the TOML date object... so either way if a time is provided this is not going to be super useful... 😕 maybe an hardcoded example could do?

This will be a TomlDate though, won't it? The toISOString method is different

oh.... you're right! 😓

And I've debugged this.... it can get pretty messy 😕

So indeed I would just put a hardcoded example 🤔

.changeset/tangy-knives-allow.md

vicb

LGTM, thanks!

(A few nit comments)

packages/workers-utils/tests/config/validation/normalize-and-validate-config.test.ts

…loudflare#11651) * fix: automatically convert TOML Date values in vars to strings TOML parses unquoted date values like DATE = 2024-01-01 as Date objects. Previously this caused a confusing error from Miniflare. Now wrangler automatically converts Date values to ISO date strings (YYYY-MM-DD format) and shows a warning suggesting to wrap the value in quotes. Co-authored-by: Dario Piotrowicz <[email protected]> * error insted of trying to convert to string * Apply suggestions from code review Co-authored-by: Victor Berchet <[email protected]> * Apply suggestions from code review Co-authored-by: Victor Berchet <[email protected]> * Apply suggestions from code review * use hardcoded example * create toml dates using smol-toml in tests --------- Co-authored-by: OpenCode Claude <[email protected]> Co-authored-by: Victor Berchet <[email protected]>

workers-devprod added this to workers-sdk Dec 15, 2025

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dario-piotrowicz marked this pull request as ready for review December 15, 2025 17:19

dario-piotrowicz requested a review from a team as a code owner December 15, 2025 17:19

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V3 Backport: fix: Automatically convert TOML Date values in vars to strings #11652

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dario-piotrowicz force-pushed the claude/7755 branch from 08d182e to 2fbaed8 Compare December 15, 2025 18:00

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dario-piotrowicz force-pushed the claude/7755 branch from 2fbaed8 to 3519de0 Compare December 15, 2025 18:11

dario-piotrowicz changed the title ~~fix: improve error message for Date values in wrangler.toml vars~~ Automatically convert TOML Date values in vars to strings Dec 15, 2025

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dario-piotrowicz force-pushed the claude/7755 branch from 3519de0 to d1875f8 Compare December 18, 2025 19:19

dario-piotrowicz changed the title ~~Automatically convert TOML Date values in vars to strings~~ Error gracefully when encountering date values in TOML config files Dec 18, 2025

dario-piotrowicz requested review from ascorbic and vicb December 18, 2025 19:20

error insted of trying to convert to string

184d673

dario-piotrowicz force-pushed the claude/7755 branch from d1875f8 to 184d673 Compare December 18, 2025 19:21

Merge branch 'main' into claude/7755

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Apply suggestions from code review

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Co-authored-by: Victor Berchet <[email protected]>

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dario-piotrowicz added 2 commits December 19, 2025 16:27

use hardcoded example

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create toml dates using smol-toml in tests

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petebacondarwin merged commit d123ad0 into main Dec 23, 2025
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github-project-automation bot moved this from Approved to Done in workers-sdk Dec 23, 2025

workers-devprod mentioned this pull request Dec 23, 2025

Version Packages #11700

Merged

Error gracefully when encountering date values in TOML config files #11651

Error gracefully when encountering date values in TOML config files #11651

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