[Isabel Duan (iisaduan)]

Missing Program API methods: https://github.com/microsoft/TypeScript/pull/64749/changes#diff-4776036ff539c2fa009621dc13a9f2c8fd15d50e9302e8a361614ab640659a2eR117

•  getProjectReferences() - Direct project references declared for the program, or  undefined  when absent.
•  getRootFileNames() - Root file names supplied when creating the program or obtained from its configuration—not imported dependencies.
• getStatistics() - Returns counts for symbols, identifiers, instantiations, nodes, and types, as well as relaction cache sizes.

Program API methods deffered:

• getSourceFiles() - Add missing Program and Project Methods #64988 (review)
• `getResolvedProjectReferences() - Add missing Program and Project Methods #64988 (comment)

Program API methods removed:

• getTypeChecker() - No longer in the ownership model
• getOptionsDiagnostics() - reduce duplicate methods
• getTypeCount, getSymbolCount, getRelationCacheSizes, getIdentifierCount, getInstantiationCount, getNodeCount- removed-- use GetStatistics(), which returns all of these

Project API Methods removed in order to reduce duplicate methods across objects

•  containsFile
•  getFileNames
•  getRootFiles
•  hasRoots,
• isRoot 
•  hasConfigFile
•  getSourceFile

[Copilot]

🟡 Changes recommended

The filesystem check incorrectly excludes in-program supplemental files without physical files, causing containsFile to return false even when getSourceFile succeeds.

1 open issue

• Check program membership before requiring filesystem existence · New

What changed in this PR

Adds missing Program and Project methods to the JavaScript API, backed by native compiler and project services.

Changes:

• Exposes program statistics, checker access, file lists, option diagnostics, and resolved project references.
• Adds project membership, root-file, and configuration-file queries.
• Updates protocol definitions and generated synchronous APIs, with behavioral and generator-parity tests.

File	Description
tsc/​internal/​project/​projectcollection.go	Checks editor- and API-open files.
tsc/​internal/​compiler/​program.go	Collects filtered option diagnostics.
tsc/​internal/​checker/​types.go	Defines relation-cache statistics.
tsc/​internal/​checker/​exports.go	Exposes relation-cache entry counts.
tsc/​internal/​api/​session.go	Implements new API request handlers.
tsc/​internal/​api/​session_program_test.go	Tests membership, statistics, and checker reuse.
tsc/​internal/​api/​proto.go	Defines new requests and response types.
packages/​typescript/​test/​sync/​api.test.ts	Adds generated synchronous API tests.
packages/​typescript/​test/​sync/​api-generators.test.ts	Checks generator parity for new methods.
packages/​typescript/​test/​async/​api.test.ts	Tests new methods and edge cases.
packages/​typescript/​src/​api/​sync/​api.ts	Adds generated synchronous and generator methods.
packages/​typescript/​src/​api/​proto.generated.ts	Updates generated protocol declarations.
packages/​typescript/​src/​api/​async/​api.ts	Implements asynchronous Program and Project methods.

_{Review effort: Balanced}

[Copilot]

🟡 Changes recommended

Concurrent cold-cache calls can return inconsistent project-reference object identities, while sequential per-file requests prevent automatic batching and add a round trip for each file.

2 open issues

• Batch source file metadata requests to avoid sequential round trips · New
• Prevent concurrent project reference graph cache overwrites · New

1 resolved since last review

• Check program membership before requiring filesystem existence

_{Review effort: Balanced}

[Copilot]

🟢 Approval recommended

No active review issues block approval of the added Program and Project API methods.

No open issues 🎉

2 resolved since last review

• Prevent concurrent project reference graph cache overwrites
• Batch source file metadata requests to avoid sequential round trips

_{Review effort: Balanced}

[Andrew Branch (andrewbranch)]

In addition to the inline comments, let's remove

• program.getSourceFiles()—not a good idea for anyone to do this pre-filtering; we'll think about an explicitly filtered and/or streaming batch API in the future
• program.getTypeChecker()—that's not the ownership model anymore, and there's no reason to make an API request for it
• all of the Project methods; they can all be done more directly off Program and ParsedCommandLine so I don't want to expand that API surface unnecessarily.

[Isabel Duan (iisaduan)]

removed GetResolvedProjectReferences to rethink its implementation later. Relevant comments for later:
#64988 (comment)
#64988 (comment)