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PolyContext

PolyContext answers "what coding environment am I in right now." It is a standalone platform mechanism — poly-symbols is its biggest consumer (gating which PolySymbolQueryScopeContributor/QueryConfigurator registrations apply), but PolyContext itself has no dependency on PolySymbols or on web frameworks being involved at all. Its defining advantage is that it is heavily optimized for performance (cached, cheap, RequiresReadLock-only), which makes it the right tool for any "is feature X relevant here" check that would otherwise get reinvented per-feature as an ad-hoc cached provider — not just "which JS framework is active." Confirmed non-web examples already in this repo: PolyContext.PKG_MANAGER_RUBY_GEMS/ PKG_MANAGER_SYMFONY_BUNDLES constants live right next to PKG_MANAGER_NODE_PACKAGES in PolyContext.kt, and ruby/tests/.../gem/GemContextTest.kt queries a "timecop-context" kind (is the timecop Ruby gem present?) with no PolySymbols query executor or web framework in sight.

For any given context kind (e.g. "framework"), at most one name is active at a location, or null if none applies.

PolyContext.get("framework", psiElement) // "vue" | "angular" | "astro" | null

Two location overloads

PolyContext.get(kind: PolyContextKind, location: PsiElement): PolyContextName?
PolyContext.get(kind: PolyContextKind, location: VirtualFile, project: Project): PolyContextName?

Location	Cost	Capability
PsiElement	normal	can inspect the PSI tree (e.g. check imports) — use for most coding-assistance logic
VirtualFile + Project	cheap, indexing-safe	no PSI access; results may legitimately differ from the PsiElement answer for the same file once parsed

The VirtualFile+Project overload is what makes PolyContext usable during language substitution — i.e. before any PSI exists for the file, when the platform is still deciding which Language to parse it as. Concrete chain in this repo: WebFrameworkHtmlLanguageSubstitutor.getLanguage(file: VirtualFile, project: Project) (a LanguageSubstitutor, plugins/JavaScriptLanguage/web-platform/.../WebFrameworkHtmlLanguageSubstitutor.kt:15) → WebFramework.forContext(file, project) → PolySymbolFramework.inLocation(file, project) (community/platform/polySymbols/shared/src/com/intellij/polySymbols/framework/PolySymbolFramework.kt:52-53) → PolyContext.get(KIND_FRAMEWORK, file, project). The result picks which HTML dialect (Vue/Angular/plain) the file's Language is substituted to, entirely before a PSI tree is built.

Canonical PolySymbols use case: web framework detection. Only one of Vue/Angular/React/Astro can be the active framework at a location, and each plugin's PolySymbolQueryScopeContributor/ QueryConfigurator gates its registrations with .inContext { it.framework == MyFramework.ID } (see poly-symbols/references/query-model.md) — but this is one consumer among many, not the reason PolyContext exists.

PolyContextProvider — direct/dynamic detection

Implement isEnabled() (or isForbidden()) and register at EP com.intellij.polySymbols.context. Results are called very often — cache them (CachedValuesManager).

PolyContext.get("stimulus-context", psiElement) == "true"

Blocking: isForbidden() with name "any" suppresses an entire context kind — e.g. a Python templating (Blade-style) blocker disables the whole framework kind so it never conflicts with Vue/Angular detection.

Real examples in this repo/docs: StimulusContextProvider (checks for a JS import, caches the result), PyTemplatesWebContextBlocker (forbids framework when Python templating is detected). For a full custom-detector example, see VueFileContextProvider (contrib/vuejs/vuejs-backend/src/org/jetbrains/vuejs/context/VueFileContextProvider.kt) — returns true unconditionally for .vue files, and for any HTML-compatible file whose <script src="..."> matches a known Vue CDN/filename pattern (a cached-value scan, not a per-call check). Angular's equivalent is AngularCliContextProvider (contrib/Angular/.../org/angular2/cli/), registered at polySymbols.context kind="framework" name="angular".

Context rules — the declarative, faster alternative

Many providers redundantly re-check the same thing (is package X a dependency?). Context rules are declarative and let the platform compute proximity once instead of running N ad-hoc providers.

Via Web Types

Under a top-level contexts-config property in a Web Types JSON file (see poly-symbols/references/web-types.md): kind → name → enable-when/disable-when. (Pre-2024.2 files use a deprecated layout where name is top-level and kind a sibling property — don't use that shape for new files.)

enable-when rule kinds: file-extensions, file-name-patterns, ide-libraries, project-tool-executables, node-packages, ruby-gems. disable-when is more limited: file-extensions, file-name-patterns only.

Proximity scoring (lower = closer/stronger match; the winning name for a kind is whichever rule has the lowest total):

• file-extensions / file-name-patterns → 0.0 (perfect match)
• ide-libraries / ruby-gems → Double.MAX_VALUE (project/module-level match)
• node-packages → computed from package.json location + dependency type: same directory as base 0.0, +1.0 per parent directory walked up, plus importance modifiers — peerDependencies +0.1, bundledDependencies +0.2, dependencies +0.3, optionalDependencies +0.4, devDependencies +0.5, indirect (node_modules) +0.6.

Web Types shipping a context rule are registered at EP com.intellij.polySymbols.webTypes (currently Node Package Manager only, requires the JS plugin) with two naming strategies: name the file after the real npm package if the rule should trigger on that package's presence, or use an arbitrary name + enableByDefault="true" if it should always apply.

Via code — PolyContextRulesProvider

For rules that can't be expressed as static file-based data, implement a PolySymbolQueryConfigurator and override getContextRulesProviders(project, dir): List<PolyContextRulesProvider> at EP com.intellij.polySymbols.queryConfigurator. Rule output must be stable — a change triggers project rescanning and cache invalidation.

.ws-context — user override file

Since 2024.1.2, users can force context values with a .ws-context JSON file:

• <context kind> → <context name> — direct top-level assignment (implicitly applies to /**).
• <GLOB path> → nested context-details object — GLOB supports only * in the final segment; ** matches nested directories.

When multiple patterns match a file, resolution priority is: (1) most path segments excluding **, (2) prefer patterns with an actual file-name match (not ending in **//), (3) first-defined wins.

PolyContextSourceProximityProvider

For integrating a new package manager or a language with a global-library concept, register at EP com.intellij.polySymbols.contextSourceProximityProvider and implement calculateProximity(), computing proximity per sourceNames entry matching a sourceKind (e.g. a dependency type). Return a Result with modificationTrackers — keep the tracker count minimal since it feeds every PolyContext.get() call.

Related

• poly-symbols — PolyContext's biggest consumer, not something it depends on.
• poly-symbols/references/web-types.md — contexts-config file format.
• Official docs: Poly Symbols Context (the only official doc page for this API — despite the URL/page name, treat it as documenting a general-purpose context mechanism, not something PolySymbols-exclusive).