add TypeScript support (#83)

Co-authored-by: Conduitry <git@chor.date>

CHANGELOG.md

@@ -1,3 +1,7 @@
+# 3.1.0 (Unreleased)
+
+- Add TypeScript support
+
 # 3.0.0
 
 - Breaking change: Node 10+ is now required

README.md

@@ -56,6 +56,52 @@ module.exports = {
 
 By default, this plugin needs to be able to `require('svelte/compiler')`. If ESLint, this plugin, and Svelte are all installed locally in your project, this should not be a problem.
 
+### Installation with TypeScript
+
+If you want to use TypeScript, you'll need a different ESLint configuration. In addition to the Svelte plugin, you also need the ESLint TypeScript parser and plugin. Install `typescript`, `@typescript-eslint/parser` and `@typescript-eslint/eslint-plugin` from npm and then adjust your config like this:
+
+```javascript
+module.exports = {
+  parser: '@typescript-eslint/parser', // add the TypeScript parser
+  plugins: [
+    'svelte3',
+    '@typescript-eslint' // add the TypeScript plugin
+  ],
+  overrides: [ // this stays the same
+    {
+      files: ['*.svelte'],
+      processor: 'svelte3/svelte3'
+    }
+  ],
+  rules: {
+    // ...
+  },
+  settings: {
+    'svelte3/typescript': require('typescript'), // pass the TypeScript package to the Svelte plugin
+    // ...
+  }
+};
+```
+
+If you also want to be able to use type-aware linting rules (which will result in slower linting, because the whole program needs to be compiled and type-checked), then you also need to add some `parserOptions` configuration. The values below assume that your ESLint config is at the root of your project next to your `tsconfig.json`. For more information, see [here](https://github.com/typescript-eslint/typescript-eslint/blob/master/docs/getting-started/linting/TYPED_LINTING.md).
+
+```javascript
+module.exports = {
+  // ...
+  parserOptions: { // add these parser options
+    tsconfigRootDir: __dirname,
+    project: ['./tsconfig.json'],
+    extraFileExtensions: ['.svelte'],
+  },
+  extends: [ // then, enable whichever type-aware rules you want to use
+    'eslint:recommended',
+    'plugin:@typescript-eslint/recommended',
+    'plugin:@typescript-eslint/recommended-requiring-type-checking'
+  ],
+  // ...
+};
+```
+
 ## Interactions with other plugins
 
 Care needs to be taken when using this plugin alongside others. Take a look at [this list of things you need to watch out for](OTHER_PLUGINS.md).
@@ -90,12 +136,18 @@ The default is to not ignore any styles.
 
 ### `svelte3/named-blocks`
 
-When an [ESLint processor](https://eslint.org/docs/user-guide/configuring#specifying-processor) processes a file, it is able to output named code blocks, which can each have their own linting configuration. When this setting is enabled, the code extracted from `<script context='module'>` tag, the `<script>` tag, and the template are respectively given the block names `module.js`, `instance.js`, and `template.js`.
+When an [ESLint processor](https://eslint.org/docs/user-guide/configuring/plugins#specifying-processor) processes a file, it is able to output named code blocks, which can each have their own linting configuration. When this setting is enabled, the code extracted from `<script context='module'>` tag, the `<script>` tag, and the template are respectively given the block names `module.js`, `instance.js`, and `template.js`.
 
 This means that to override linting rules in Svelte components, you'd instead have to target `**/*.svelte/*.js`. But it also means that you can define an override targeting `**/*.svelte/*_template.js` for example, and that configuration will only apply to linting done on the templates in Svelte components.
 
 The default is to not use named code blocks.
 
+### `svelte3/typescript`
+
+If you use TypeScript inside your Svelte components and want ESLint support, you need to set this option. It expects an instance of the TypeScript package. This probably means doing `'svelte3/typescript': require('typescript')`.
+
+The default is to not enable TypeScript support.
+
 ### `svelte3/compiler`
 
 In some esoteric setups, this plugin might not be able to find the correct instance of the Svelte compiler to use.

package.json

@@ -34,8 +34,13 @@
 		"test": "npm run build && node test"
 	},
 	"devDependencies": {
+		"@rollup/plugin-node-resolve": "^11.2.0",
+		"@typescript-eslint/eslint-plugin": "^4.14.2",
+		"@typescript-eslint/parser": "^4.14.2",
 		"eslint": ">=6.0.0",
 		"rollup": "^2",
-		"svelte": "^3.2.0"
+		"sourcemap-codec": "1.4.8",
+		"svelte": "^3.2.0",
+		"typescript": "^4.0.0"
 	}
 }

rollup.config.js

@@ -1,4 +1,7 @@
+import node_resolve from '@rollup/plugin-node-resolve';
+
 export default {
 	input: 'src/index.js',
 	output: { file: 'index.js', format: 'cjs' },
+	plugins: [ node_resolve() ],
 };

src/mapping.js

@@ -0,0 +1,206 @@
+import { decode } from 'sourcemap-codec';
+
+class GeneratedFragmentMapper {
+	constructor(generated_code, diff) {
+		this.generated_code = generated_code;
+		this.diff = diff;
+	}
+
+	get_position_relative_to_fragment(position_relative_to_file) {
+		const fragment_offset = this.offset_in_fragment(offset_at(position_relative_to_file, this.generated_code));
+		return position_at(fragment_offset, this.diff.generated_content);
+	}
+
+	offset_in_fragment(offset) {
+		return offset - this.diff.generated_start
+	}
+}
+
+class OriginalFragmentMapper {
+	constructor(original_code, diff) {
+		this.original_code = original_code;
+		this.diff = diff;
+	}
+
+	get_position_relative_to_file(position_relative_to_fragment) {
+		const parent_offset = this.offset_in_parent(offset_at(position_relative_to_fragment, this.diff.original_content));
+		return position_at(parent_offset, this.original_code);
+	}
+
+	offset_in_parent(offset) {
+		return this.diff.original_start + offset;
+	}
+}
+
+class SourceMapper {
+	constructor(raw_source_map) {
+		this.raw_source_map = raw_source_map;
+	}
+
+	get_original_position(generated_position) {
+		if (generated_position.line < 0) {
+			return { line: -1, column: -1 };
+		}
+
+		// Lazy-load
+		if (!this.decoded) {
+			this.decoded = decode(JSON.parse(this.raw_source_map).mappings);
+		}
+
+		let line = generated_position.line;
+		let column = generated_position.column;
+
+		let line_match = this.decoded[line];
+		while (line >= 0 && (!line_match || !line_match.length)) {
+			line -= 1;
+			line_match = this.decoded[line];
+			if (line_match && line_match.length) {
+				return {
+					line: line_match[line_match.length - 1][2],
+					column: line_match[line_match.length - 1][3]
+				};
+			}
+		}
+
+		if (line < 0) {
+			return { line: -1, column: -1 };
+		}
+
+		const column_match = line_match.find((col, idx) =>
+			idx + 1 === line_match.length ||
+			(col[0] <= column && line_match[idx + 1][0] > column)
+		);
+
+		return {
+			line: column_match[2],
+			column: column_match[3],
+		};
+	}
+}
+
+export class DocumentMapper {
+	constructor(original_code, generated_code, diffs) {
+		this.original_code = original_code;
+		this.generated_code = generated_code;
+		this.diffs = diffs;
+		this.mappers = diffs.map(diff => {
+			return {
+				start: diff.generated_start,
+				end: diff.generated_end,
+				diff: diff.diff,
+				generated_fragment_mapper: new GeneratedFragmentMapper(generated_code, diff),
+				source_mapper: new SourceMapper(diff.map),
+				original_fragment_mapper: new OriginalFragmentMapper(original_code, diff)
+			}
+		});
+	}
+
+	get_original_position(generated_position) {
+		generated_position = { line: generated_position.line - 1, column: generated_position.column };
+		const offset = offset_at(generated_position, this.generated_code);
+		let original_offset = offset;
+		for (const mapper of this.mappers) {
+			if (offset >= mapper.start && offset <= mapper.end) {
+				return this.map(mapper, generated_position);
+			}
+			if (offset > mapper.end) {
+				original_offset -= mapper.diff;
+			}
+		}
+		const original_position = position_at(original_offset, this.original_code);
+		return this.to_ESLint_position(original_position);
+	}
+
+	map(mapper, generated_position) {
+		// Map the position to be relative to the transpiled fragment
+		const position_in_transpiled_fragment = mapper.generated_fragment_mapper.get_position_relative_to_fragment(
+			generated_position
+		);
+		// Map the position, using the sourcemap, to the original position in the source fragment
+		const position_in_original_fragment = mapper.source_mapper.get_original_position(
+			position_in_transpiled_fragment
+		);
+		// Map the position to be in the original fragment's parent
+		const original_position = mapper.original_fragment_mapper.get_position_relative_to_file(position_in_original_fragment);
+		return this.to_ESLint_position(original_position);
+	}
+
+	to_ESLint_position(position) {
+		// ESLint line/column is 1-based
+		return { line: position.line + 1, column: position.column + 1 };
+	}
+
+}
+
+/**
+ * Get the offset of the line and character position
+ * @param position Line and character position
+ * @param text The text for which the offset should be retrieved
+ */
+function offset_at(position, text) {
+	const line_offsets = get_line_offsets(text);
+
+	if (position.line >= line_offsets.length) {
+		return text.length;
+	} else if (position.line < 0) {
+		return 0;
+	}
+
+	const line_offset = line_offsets[position.line];
+	const next_line_offset =
+		position.line + 1 < line_offsets.length ? line_offsets[position.line + 1] : text.length;
+
+	return clamp(next_line_offset, line_offset, line_offset + position.column);
+}
+
+function position_at(offset, text) {
+	offset = clamp(offset, 0, text.length);
+
+	const line_offsets = get_line_offsets(text);
+	let low = 0;
+	let high = line_offsets.length;
+	if (high === 0) {
+		return { line: 0, column: offset };
+	}
+
+	while (low < high) {
+		const mid = Math.floor((low + high) / 2);
+		if (line_offsets[mid] > offset) {
+			high = mid;
+		} else {
+			low = mid + 1;
+		}
+	}
+
+	// low is the least x for which the line offset is larger than the current offset
+	// or array.length if no line offset is larger than the current offset
+	const line = low - 1;
+	return { line, column: offset - line_offsets[line] };
+}
+
+function get_line_offsets(text) {
+	const line_offsets = [];
+	let is_line_start = true;
+
+	for (let i = 0; i < text.length; i++) {
+		if (is_line_start) {
+			line_offsets.push(i);
+			is_line_start = false;
+		}
+		const ch = text.charAt(i);
+		is_line_start = ch === '\r' || ch === '\n';
+		if (ch === '\r' && i + 1 < text.length && text.charAt(i + 1) === '\n') {
+			i++;
+		}
+	}
+
+	if (is_line_start && text.length > 0) {
+		line_offsets.push(text.length);
+	}
+
+	return line_offsets;
+}
+
+function clamp(num, min, max) {
+	return Math.max(min, Math.min(max, num));
+}