Start building import-locality

packages/steiger-plugin-fsd/src/import-locality/index.ts

@@ -0,0 +1,69 @@
+import * as fs from 'node:fs'
+import { relative, join } from 'node:path'
+import { resolveImport } from '@feature-sliced/filesystem'
+import precinct from 'precinct'
+const { paperwork } = precinct
+import { parse as parseNearestTsConfig } from 'tsconfck'
+
+import type { Diagnostic, Rule } from '../types.js'
+import { indexSourceFiles } from '../_lib/index-source-files.js'
+
+const importLocality = {
+  name: 'import-locality',
+  async check(root) {
+    const diagnostics: Array<Diagnostic> = []
+    const { tsconfig } = await parseNearestTsConfig(root.path)
+    const sourceFileIndex = indexSourceFiles(root)
+
+    for (const sourceFile of Object.values(sourceFileIndex)) {
+      const dependencies = paperwork(sourceFile.file.path, { includeCore: false, fileSystem: fs })
+      for (const dependency of dependencies) {
+        const resolvedDependency = resolveImport(
+          dependency,
+          sourceFile.file.path,
+          tsconfig?.compilerOptions ?? {},
+          fs.existsSync,
+          fs.existsSync,
+        )
+        if (resolvedDependency === null) {
+          continue
+        }
+
+        const dependencyLocation = sourceFileIndex[resolvedDependency]
+        if (dependencyLocation === undefined) {
+          continue
+        }
+
+        const isRelative = ['.', '..'].includes(dependency.split('/')[0])
+        const isWithinSameSlice =
+          sourceFile.layerName === dependencyLocation.layerName && sourceFile.sliceName === dependencyLocation.sliceName
+
+        if (isRelative && !isWithinSameSlice) {
+          const sourceRelativePath = relative(root.path, sourceFile.file.path)
+          const dependencyRelativePath = relative(root.path, dependencyLocation.file.path)
+          diagnostics.push({
+            message: `Import from "${sourceRelativePath}" to "${dependencyRelativePath} should not be relative.`,
+          })
+        } else if (!isRelative && isWithinSameSlice) {
+          const sourceRelativePath = relative(
+            join(...[root.path, sourceFile.layerName, sourceFile.sliceName].filter(Boolean)),
+            sourceFile.file.path,
+          )
+          const dependencyRelativePath = relative(
+            join(...[root.path, dependencyLocation.layerName, dependencyLocation.sliceName].filter(Boolean)),
+            dependencyLocation.file.path,
+          )
+          const layerAndSlice = join(...[dependencyLocation.layerName, dependencyLocation.sliceName].filter(Boolean))
+
+          diagnostics.push({
+            message: `Import from "${sourceRelativePath}" to "${dependencyRelativePath}" on "${layerAndSlice}" should be relative.`,
+          })
+        }
+      }
+    }
+
+    return { diagnostics }
+  },
+} satisfies Rule
+
+export default importLocality