fix(theme): support ESM import for v5 compatibility theme

[pratik-desgn]

Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

Adds an ESM-compatible v5 theme entry and conditional package exports so ESM imports register the theme on the application's ECharts module instance while existing CommonJS, AMD, and browser-global consumers keep using the current UMD entry.

Fixed issues

• [Bug] v6 migration guide v5 theme import fails in Webpack 5 #21757: Fix v5 compatibility theme imports in strict Webpack 5 ESM applications.

Details

Before: What was the problem?

The v5 theme entry is a UMD/CommonJS file that imports echarts/lib/echarts. When an application imports the ESM ECharts entry, Webpack can bundle a second ECharts module instance for the theme. The theme is then registered on that second instance and the chart continues using the ECharts 6 defaults.

The extensionless package export also has no concrete target.

After: How does it behave after the fixing?

The import condition for both echarts/theme/v5 and echarts/theme/v5.js now resolves to theme/v5.mjs, which registers through the package's ESM core entry. The require and default conditions remain on theme/v5.js, preserving the existing non-ESM entry points. The ESM file is marked as a side effect so bundlers retain the registration.

Document Info

• This PR doesn't relate to document changes
• The document should be updated later
• The document changes have been made in apache/echarts-doc#xxx

Misc

Security Checking

• This PR uses security-sensitive Web APIs.

ZRender Changes

• This PR depends on ZRender changes.

Related test cases or examples to use the new APIs

Validated with the ECharts 6.1.0 package in Webpack 5.110.3:

• The baseline bundle includes the legacy UMD theme wrapper; the patched bundle resolves the ESM entry.
• Node ESM imports of both echarts/theme/v5 and echarts/theme/v5.js register the expected v5 palette.
• TZ=UTC npm test -- --runInBand: 26 suites, 194 tests passed.
• node --check theme/v5.mjs, node build/checkHeader.js, npm pack --dry-run --ignore-scripts, and git diff --check pass.

The normal npm run build:lib check is currently blocked by the checkout's existing TypeScript 4.4/dependency mismatch: installed newer @types/node and Babel declarations are rejected before this change is compiled.

Merging options

• Please squash the commits into a single one when merging.

Other information

The commit includes the Apache-recommended Generated-by: OpenAI Codex provenance trailer.

[echarts-bot]

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