Update to Go 1.27

[Jake Bailey (jakebailey)]

Lotsa goodies

[Copilot]

Pull request overview

Updates the compiler and tooling to Go 1.27 and adopts its standard-library and modernization features.

Changes:

• Raises Go requirements and refreshes dependencies/tooling.
• Migrates to encoding/json/v2.
• Applies Go 1.27 struct-literal and reverse-iteration simplifications.

Reviewed changes

Copilot reviewed 63 out of 65 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tsc/internal/tsoptions/tsconfigparsing.go	Uses reverse-slice iteration.
tsc/internal/tsoptions/tsconfigparsing_test.go	Simplifies embedded-field literals.
tsc/internal/tsoptions/contentmappers_test.go	Simplifies mapper literals.
tsc/internal/transformers/estransforms/taggedtemplate.go	Uses slices.Clip.
tsc/internal/testutil/contentmappertest/transforming.go	Flattens result literals.
tsc/internal/testutil/contentmappertest/synthesizing.go	Flattens result literals.
tsc/internal/testutil/contentmappertest/supplemental.go	Flattens output literals.
tsc/internal/testutil/contentmappertest/supplemental_module.go	Flattens supplemental outputs.
tsc/internal/testutil/contentmappertest/supplemental_globals.go	Flattens supplemental outputs.
tsc/internal/testutil/contentmappertest/supplemental_diagnostics.go	Flattens supplemental outputs.
tsc/internal/testutil/contentmappertest/mapper_test.go	Simplifies mapper construction.
tsc/internal/testutil/contentmappertest/lisp.go	Flattens result literals.
tsc/internal/testutil/contentmappertest/editing.go	Flattens mapped outputs.
tsc/internal/testutil/contentmappertest/duplicate.go	Flattens result literals.
tsc/internal/testutil/contentmappertest/component.go	Flattens result literal.
tsc/internal/testutil/autoimporttestutil/fixtures.go	Simplifies embedded file handle.
tsc/internal/pseudochecker/lookup.go	Uses reverse-slice iteration.
tsc/internal/project/snapshotfs.go	Simplifies disk-file literal.
tsc/internal/project/session.go	Flattens resource requests.
tsc/internal/project/refcountcache_test.go	Simplifies embedded-field literals.
tsc/internal/project/overlayfs.go	Simplifies embedded file bases.
tsc/internal/project/logging/logcollector.go	Flattens logger literal.
tsc/internal/project/dirty/syncmap.go	Flattens map-entry literals.
tsc/internal/project/dirty/map.go	Flattens map-entry literals.
tsc/internal/project/contentmapper_test.go	Simplifies mapper fixtures.
tsc/internal/project/api.go	Flattens resource request.
tsc/internal/printer/utilities.go	Uses reverse-slice iteration.
tsc/internal/printer/changetrackerwriter.go	Flattens writer literal.
tsc/internal/modulespecifiers/specifiers_test.go	Flattens JSON-value literal.
tsc/internal/lsp/server.go	Simplifies mapper construction.
tsc/internal/ls/symbols.go	Uses reverse-slice iteration.
tsc/internal/ls/lsutil/formatcodeoptions.go	Flattens default editor settings.
tsc/internal/ls/lsutil/children.go	Uses reverse-slice iteration.
tsc/internal/ls/lsconv/converters.go	Flattens mapped-span literal.
tsc/internal/ls/findallreferences.go	Flattens position literal.
tsc/internal/ls/documenthighlights.go	Uses reverse-slice iteration.
tsc/internal/ls/autoimport/registry_test.go	Simplifies embedded fixture templates.
tsc/internal/ls/autoimport/extract.go	Flattens export identifier.
tsc/internal/json/json.go	Adopts standard encoding/json/v2.
tsc/internal/fswatch/watcher.go	Modernizes rollback iteration.
tsc/internal/fourslash/test_parser.go	Flattens location literal.
tsc/internal/fourslash/fourslash.go	Modernizes reverse edit iteration.
tsc/internal/format/span.go	Modernizes reverse rule iteration.
tsc/internal/format/format_test.go	Flattens formatting settings.
tsc/internal/format/comment_test.go	Flattens formatting fixtures.
tsc/internal/format/api_test.go	Flattens formatting fixtures.
tsc/internal/execute/tsc/diagnostics.go	Flattens path-formatting options.
tsc/internal/execute/incremental/buildinfo_contentmapper_test.go	Simplifies mapper fixtures.
tsc/internal/core/core.go	Modernizes reverse search helpers.
tsc/internal/contentmapper/transform_test.go	Simplifies mapper fixtures.
tsc/internal/contentmapper/host_test.go	Simplifies mapper and output fixtures.
tsc/internal/compiler/contentmapper_test.go	Simplifies mapper fixture.
tsc/internal/checker/checker.go	Modernizes reverse context lookup.
tsc/internal/astnav/tokens.go	Modernizes reverse token lookup.
tsc/go.sum	Refreshes compiler dependency checksums.
tsc/go.mod	Requires Go 1.27 and updates dependencies.
tools/go.sum	Refreshes tooling dependency checksums.
tools/go.mod	Requires Go 1.27 and updates tooling.
tools/customlint/testdata/go.mod	Updates custom-linter test module.
NOTICE.txt	Updates dependency notices.
go.work	Requires Go 1.27 workspace-wide.
CONTRIBUTING.md	Documents Go 1.27 prerequisite.
.golangci.yml	Enables new modernization and guards JSON v2.
.github/actions/setup-go/action.yml	Installs Go 1.27 in CI.
.custom-gcl.yml	Updates custom golangci-lint version.

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[Jake Bailey (jakebailey)]

There's a new version that'll parse generic methods, but we need to wait a week for the npm quarantine.

It's probably best to wait anyway because linters are still getting bugfixes.

[Jake Bailey (jakebailey)]

Acknowledged. I am leaving @jakebailey/dprint-plugin-gofumpt at 0.0.13 for now and will avoid adopting generic methods in this PR.

[Copilot]

Pull request overview

Copilot reviewed 64 out of 79 changed files in this pull request and generated 2 comments.

[Jake Bailey (jakebailey)]

There is not yet a published dev-1.27-bookworm image, so I added GOTOOLCHAIN=go1.27.0 to the devcontainer environment while retaining the Go 1.26 base image. This makes the temporary local toolchain choice explicit and reproducible.

[Jake Bailey (jakebailey)]

Sadly, the devcontainer is not out