feature(terraform): Parse and auto detect TF module dependencies (#298)

It could be tedious to manually manage all terraform module calls as
dependencies for larger projects. This parses the HCL source to identify
and add direct static dependencies to the NX dependency graph.

packages/terraform/package.json

@@ -19,5 +19,8 @@
     "@nx/devkit": "^19.6.0"
   },
   "builders": "./executors.json",
-  "generators": "./generators.json"
+  "generators": "./generators.json",
+  "dependencies": {
+    "hcl2-json-parser": "^1.0.1"
+  }
 }

packages/terraform/src/graph.ts

@@ -0,0 +1,76 @@
+import {
+  CreateDependencies,
+  logger,
+  RawProjectGraphDependency,
+  workspaceRoot
+} from '@nx/devkit'
+import * as hcl2JsonParser from 'hcl2-json-parser'
+import * as fs from 'node:fs/promises'
+import * as path from 'node:path'
+import { DependencyType } from 'nx/src/config/project-graph'
+
+const isLocalPath = (path: string) => {
+  return path.startsWith('./') || path.startsWith('../')
+}
+
+export const createDependencies: CreateDependencies = async (_, ctx) => {
+  const results: RawProjectGraphDependency[] = []
+
+  const projectRootsToProject: [projectRoot: string, name: string][] =
+    Object.entries(ctx.projects).map(([name, project]) => [project.root, name])
+
+  for (const project of Object.keys(ctx.projects)) {
+    // find tf files to process in the project
+    const tfFilesToProcess =
+      ctx.filesToProcess.projectFileMap[project]?.filter((file) =>
+        file.file.endsWith('.tf')
+      ) ?? []
+
+    for (const file of tfFilesToProcess) {
+      const data = await fs.readFile(file.file)
+
+      let parsed: hcl2JsonParser.HclDef
+
+      try {
+        parsed = await hcl2JsonParser.parseToObject(data.toString())
+      } catch (e) {
+        logger.warn(
+          `Failed to parse .tf file ${file.file}. Error: ${e.message}`
+        )
+        continue
+      }
+
+      for (const moduleCall of Object.values(parsed.module ?? [])) {
+        const depSourcePathRel = moduleCall[0]?.source
+
+        if (!isLocalPath(depSourcePathRel)) {
+          continue
+        }
+
+        const depSourceAbs = path.resolve(file.file, depSourcePathRel)
+
+        const depSourceRelativeToWorkspace = path.relative(
+          workspaceRoot,
+          depSourceAbs
+        )
+
+        const targetProject = projectRootsToProject.find(([root]) =>
+          depSourceRelativeToWorkspace.startsWith(root)
+        )?.[1]
+
+        if (!targetProject || targetProject === project) {
+          continue
+        }
+
+        results.push({
+          type: DependencyType.static,
+          source: project,
+          target: targetProject,
+          sourceFile: file.file
+        })
+      }
+    }
+  }
+
+  return results
+}

packages/terraform/src/hcl2-json-parser.d.ts

@@ -0,0 +1,27 @@
+declare module 'hcl2-json-parser' {
+  export type HclDef = {
+    data?: {
+      [data: string]: {
+        [dataName: string]: [{ [propertyName: string]: any }]
+      }
+    }
+
+    resource?: {
+      [resource: string]: {
+        [resourceName: string]: [{ [propertyName: string]: any }]
+      }
+    }
+
+    terraform?: [
+      {
+        backend?: [{ [propertyName: string]: any }]
+      }
+    ]
+
+    module?: {
+      [moduleName: string]: [{ source: string }]
+    }
+  }
+
+  export function parseToObject(data: string): Promise<HclDef>
+}

packages/terraform/src/index.ts

@@ -0,0 +1 @@
+export * from './graph'