feat: add shell languages

[nzakas]

Adds the ESLint language implementation, so ESLint can lint shell scripts with this plugin's parser. After this PR the plugin works end to end; it just has no rules yet.

What's included

• ShellLanguage (src/languages/shell-language.ts):
  • Text file type with 1-based lines and columns.
  • A mode constructor option ("bash" default, "posix", "mksh") selects the shell dialect. Unknown modes throw a TypeError. There are no language options.
  • Syntax errors come back as a failed parse result with line and column, which ESLint reports as a fatal message.
• ShellSourceCode (src/languages/shell-source-code.ts), built on TextSourceCodeBase from @eslint/plugin-kit:
  • getLoc() and getRange() compute positions from each node's start/end, using a lazily built line index.
  • traverse() builds the enter/exit steps once and records parents, which back getParent() and getAncestors().
  • Inline configuration from comments: # eslint-disable, -enable, -disable-line, and -disable-next-line (with -- justification), plus # eslint rule: severity.
• src/visitor-keys.ts: traversal order for all 42 node types.
• src/types.ts: adds ShellLanguageOptions, a typed ShellRuleVisitor (per-node handlers plus :exit variants), and ShellRuleDefinition, built on plugin-kit's CustomRuleDefinitionType.
• src/index.ts:
  • Registers one language per shell dialect (shell/bash, shell/posix, and shell/mksh), an empty rules map, and configs.recommended.
  • The recommended config targets **/*.sh and **/*.bash, uses language: "shell/bash", and references the plugin itself. It has no rules yet; each rule PR adds its own entry.
  • Also exports ShellLanguage, ShellSourceCode, and visitorKeys.
• README: Usage, Languages, and Configuration comments sections. The comment examples mention rules added later in the stack.

Integration tests

These tests use tests/fixtures/test-plugin.ts, a test-only plugin with two trivial rules (test/no-forbidden, test/no-deprecated), so they don't depend on any shipped rule.

• tests/plugin.test.ts:
  • Reported positions, including after non-ASCII text.
  • Traversal into nested statements and command substitutions.
  • Fatal parse errors.
  • That each language parses its own dialect.
  • That the recommended config applies to .sh/.bash and not .js. This test uses code that is valid JavaScript but invalid Bash, so it can actually tell the difference.
• tests/directives.test.ts: every disable/enable directive form, unused-directive reporting, and inline severity and enable comments.

Testing

54 new tests (136 total); build, lint, and format checks pass.

🤖 Generated with Claude Code

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📥 Commits

Reviewing files that changed from the base of the PR and between 8840b5f and 792a34e.

📒 Files selected for processing (14)

• README.md
• src/index.spec.ts
• src/index.ts
• src/languages/shell-language.spec.ts
• src/languages/shell-language.ts
• src/languages/shell-source-code.spec.ts
• src/languages/shell-source-code.ts
• src/types.spec.ts
• src/types.ts
• src/visitor-keys.spec.ts
• src/visitor-keys.ts
• tests/directives.test.ts
• tests/fixtures/test-plugin.ts
• tests/plugin.test.ts

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Copilot review overview

🟡 Changes recommended

The public visitor type exposes a Comment callback even though comments are intentionally excluded from traversal.

Review effort: Balanced
Findings: 1

Open (1)

• Remove unreachable Comment from rule visitor contract · New

What changed in this PR

Adds end-to-end ESLint language support for parsing and linting Bash files.

Changes:

• Implements Bash language parsing, source locations, traversal, and directives.
• Exposes typed rule APIs, visitor keys, and recommended configuration.
• Adds unit and integration coverage plus usage documentation.

File	Description
src/​languages/​bash-language.ts	Implements the ESLint language interface.
src/​languages/​bash-language.spec.ts	Tests language behavior and variants.
src/​languages/​bash-source-code.ts	Implements traversal, locations, and directives.
src/​languages/​bash-source-code.spec.ts	Tests source-code APIs.
src/​visitor-keys.ts	Defines AST traversal keys.
src/​visitor-keys.spec.ts	Tests visitor-key coverage.
src/​types.ts	Adds language and rule types.
src/​types.spec.ts	Tests exported types.
src/​index.ts	Registers and exports the language.
src/​index.spec.ts	Tests plugin exports and configuration.
tests/​fixtures/​test-plugin.ts	Provides test-only Bash rules.
tests/​plugin.test.ts	Tests ESLint integration.
tests/​directives.test.ts	Tests inline configuration directives.
README.md	Documents usage and options.

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