[Christopher Plieger (cplieger)]

parseConfig reports TS18000 when a config's extends chain returns to a config already on the resolution stack, but it passes no argument for the message's {0}. The text then reads Circularity detected while resolving configuration: {0} on the CLI and through the API.

Impact: the message names no config, so in a repository with many configs the user has to find the cycle by hand, and a tool on the API shows the raw placeholder.

parseConfig now passes the configs of the cycle, from the first one on the resolution stack to the config that closes it, joined with ->. Strada's parseConfig passes the whole stack. Here an extended config's parse, with its errors, is cached by path and reused by every project that reaches it, so the whole stack would name the project that filled the cache. The cycle alone holds for every project that reaches it, so a reused entry still names the right configs, though it may start the cycle at another of them. The paths are the stack's path keys.

TestParseJsonSourceFileConfigFileContentReportsCircularExtendsChain parses tsconfig.json, which extends a.json, where a.json and b.json extend each other, and expects one TS18000 whose argument is /project/a.json -> /project/b.json -> /project/a.json. On main the diagnostic has no argument.

I met this while building deadset-ts, the TypeScript analyzer of deadset, on the TypeScript 7 API, and noted it in #64755 and #64825 as a separate cause.

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Fixes #65094

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🟢 Approval recommended

No active review issues are reported for the change to include the circular configuration chain in TS18000 diagnostics.

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What changed in this PR

Fixes TS18000’s unfilled {0} placeholder by including the circular configuration chain. Reporting only the cycle keeps the message relevant when cached errors are reused by other projects.

Changes:

• Formats the cycle’s config paths with ->, including the path that closes the cycle.
• Adds a regression test verifying the diagnostic argument excludes the project leading into the cycle.

File	Description
tsc/​internal/​tsoptions/​tsconfigparsing.go	Supplies the cycle path chain to TS18000.
tsc/​internal/​tsoptions/​tsconfigparsing_test.go	Verifies one circularity diagnostic with the expected cycle argument.

_{Review effort: Balanced}