🐛 Resolve string variables in route paths (#66)

Author: savannahostrowski

src/core/analyzer.ts

@@ -5,6 +5,7 @@
 import type { Tree } from "web-tree-sitter"
 import { logError } from "../utils/logger"
 import {
+  collectStringVariables,
   decoratorExtractor,
   findNodesByType,
   importExtractor,
@@ -20,6 +21,16 @@ function notNull<T>(value: T | null): value is T {
   return value !== null
 }
 
+function resolveVariables(
+  path: string,
+  variables: Map<string, string>,
+): string {
+  return path.replace(
+    /\{([^}]+)\}/g,
+    (match, name) => variables.get(name) ?? match,
+  )
+}
+
 /** Analyze a syntax tree and extract FastAPI-related information */
 export function analyzeTree(tree: Tree, filePath: string): FileAnalysis {
   const rootNode = tree.rootNode
@@ -44,7 +55,29 @@ export function analyzeTree(tree: Tree, filePath: string): FileAnalysis {
     .map(importExtractor)
     .filter(notNull)
 
-  return { filePath, routes, routers, includeRouters, mounts, imports }
+  const stringVariables = collectStringVariables(rootNode)
+
+  for (const route of routes) {
+    route.path = resolveVariables(route.path, stringVariables)
+  }
+  for (const router of routers) {
+    router.prefix = resolveVariables(router.prefix, stringVariables)
+  }
+  for (const ir of includeRouters) {
+    ir.prefix = resolveVariables(ir.prefix, stringVariables)
+  }
+  for (const mount of mounts) {
+    mount.path = resolveVariables(mount.path, stringVariables)
+  }
+
+  return {
+    filePath,
+    routes,
+    routers,
+    includeRouters,
+    mounts,
+    imports,
+  }
 }
 
 /** Analyze a file given its URI string and a parser instance */

src/core/extractors.ts

@@ -33,6 +33,39 @@ function collectNodesByType(node: Node, type: string, results: Node[]): void {
   }
 }
 
+/**
+ * Collects string variable assignments from the AST for path resolution.
+ * Only resolves simple assignments (e.g. `WEBHOOK_PATH = "/webhook"`).
+ *
+ * Examples:
+ *   WEBHOOK_PATH = "/webhook"  -> Map { "WEBHOOK_PATH" => "/webhook" }
+ *   BASE = "/api"              -> Map { "BASE" => "/api" }
+ *   settings.PREFIX = "/api"   -> (skipped, not a simple identifier)
+ */
+export function collectStringVariables(rootNode: Node): Map<string, string> {
+  const variables = new Map<string, string>()
+  const assignmentNodes = findNodesByType(rootNode, "assignment")
+
+  for (const assign of assignmentNodes) {
+    const left = assign.childForFieldName("left")
+    const right = assign.childForFieldName("right")
+    if (
+      left &&
+      right &&
+      left.type === "identifier" &&
+      right.type === "string"
+    ) {
+      const varName = left.text
+      const value = extractStringValue(right)
+      if (value !== null) {
+        variables.set(varName, value)
+      }
+    }
+  }
+
+  return variables
+}
+
 /**
  * Extracts the string value from a string AST node, handling quotes and f-string prefix.
  * Returns null if the node is not a string.

src/test/core/analyzer.test.ts

@@ -100,6 +100,88 @@ import os
       assert.strictEqual(routesImport.isRelative, true)
     })
 
+    test("resolves same-file string variables in route paths", () => {
+      const code = `
+from fastapi import FastAPI
+
+app = FastAPI()
+
+WEBHOOK_PATH = "/webhook"
+
+@app.post(WEBHOOK_PATH)
+def some_webhook():
+    pass
+`
+      const tree = parse(code)
+      const result = analyzeTree(tree, "/test/file.py")
+
+      assert.strictEqual(result.routes.length, 1)
+      assert.strictEqual(result.routes[0].path, "/webhook")
+    })
+
+    test("resolves variable used in path concatenation", () => {
+      const code = `
+from fastapi import FastAPI
+
+app = FastAPI()
+
+BASE = "/api"
+
+@app.get(BASE + "/users")
+def list_users():
+    pass
+`
+      const tree = parse(code)
+      const result = analyzeTree(tree, "/test/file.py")
+
+      assert.strictEqual(result.routes.length, 1)
+      assert.strictEqual(result.routes[0].path, "/api/users")
+    })
+
+    test("leaves unresolvable variables wrapped", () => {
+      const code = `
+from fastapi import FastAPI
+
+app = FastAPI()
+
+@app.get(settings.API_PREFIX)
+def handler():
+    pass
+`
+      const tree = parse(code)
+      const result = analyzeTree(tree, "/test/file.py")
+
+      assert.strictEqual(result.routes.length, 1)
+      assert.strictEqual(result.routes[0].path, "{settings.API_PREFIX}")
+    })
+
+    test("resolves variable in router prefix", () => {
+      const code = `
+from fastapi import APIRouter
+
+PREFIX = "/users"
+router = APIRouter(prefix=PREFIX)
+`
+      const tree = parse(code)
+      const result = analyzeTree(tree, "/test/file.py")
+
+      const apiRouter = result.routers.find((r) => r.type === "APIRouter")
+      assert.ok(apiRouter)
+      assert.strictEqual(apiRouter.prefix, "/users")
+    })
+
+    test("resolves variable in include_router prefix", () => {
+      const code = `
+USERS_PREFIX = "/users"
+app.include_router(users.router, prefix=USERS_PREFIX)
+`
+      const tree = parse(code)
+      const result = analyzeTree(tree, "/test/file.py")
+
+      assert.strictEqual(result.includeRouters.length, 1)
+      assert.strictEqual(result.includeRouters[0].prefix, "/users")
+    })
+
     test("sets filePath correctly", () => {
       const code = "x = 1"
       const tree = parse(code)

src/test/providers/pathOperationTreeProvider.test.ts

@@ -334,6 +334,34 @@ suite("PathOperationTreeProvider", () => {
     }
   })
 
+  test("route tooltip strips dynamic prefix", () => {
+    const app = makeApp("app", "main.py")
+    app.routes = [
+      {
+        method: "GET",
+        path: "{settings.API_V1_STR}/users/{user_id}",
+        functionName: "get_user",
+        location: { filePath: "users.py", line: 10, column: 0 },
+      },
+    ]
+    const p = new PathOperationTreeProvider([app])
+    const appItem = p.getChildren()[0]
+    const route = p.getChildren(appItem).find((c) => c.type === "route")!
+    const treeItem = p.getTreeItem(route)
+    const tooltipValue =
+      typeof treeItem.tooltip === "string"
+        ? treeItem.tooltip
+        : (treeItem.tooltip as { value: string }).value
+    assert.ok(
+      tooltipValue.includes("GET /users/{user_id}"),
+      "Tooltip should show stripped path",
+    )
+    assert.ok(
+      !tooltipValue.includes("settings.API_V1_STR"),
+      "Tooltip should not include dynamic prefix",
+    )
+  })
+
   test("getChildren returns message when no apps", () => {
     const emptyProvider = new PathOperationTreeProvider([])
     const roots = emptyProvider.getChildren()

src/vscode/pathOperationTreeProvider.ts

@@ -268,8 +268,9 @@ export class PathOperationTreeProvider
         routeItem.description = element.route.functionName
         routeItem.iconPath = new ThemeIcon(METHOD_ICONS[element.route.method])
         routeItem.contextValue = "route"
+        const tooltipPath = stripLeadingDynamicSegments(element.route.path)
         routeItem.tooltip = new MarkdownString(
-          `${element.route.method} ${element.route.path}\n\nFunction: ${element.route.functionName}\nFile: ${element.route.location.filePath}:${element.route.location.line}`,
+          `${element.route.method} ${tooltipPath}\n\nFunction: ${element.route.functionName}\nFile: ${element.route.location.filePath}:${element.route.location.line}`,
         )
         routeItem.command = {
           command: "fastapi-vscode.goToPathOperation",