fix(gatsby): handle case of changing page path casing on case-insensi…

…tive fs (#31071) (#31082)

* fix(gatsby): handle case of changing page path casing on case-insensitive fs

* figure out if platform is case insenstive once and not for every page separately

* add tests for casing ... cases

(cherry picked from commit 940eddf)

Co-authored-by: Michal Piechowiak <misiek.piechowiak@gmail.com>

packages/gatsby/src/commands/__tests__/build-utils.ts

@@ -4,14 +4,21 @@ import {
   IHtmlFileState,
   IStaticQueryResultState,
 } from "../../redux/types"
-import { calcDirtyHtmlFiles } from "../build-utils"
 
+const platformSpy = jest.spyOn(require(`os`), `platform`)
 interface IMinimalStateSliceForTest {
   html: IGatsbyState["html"]
   pages: IGatsbyState["pages"]
 }
 
 describe(`calcDirtyHtmlFiles`, () => {
+  let calcDirtyHtmlFiles
+  beforeEach(() => {
+    jest.isolateModules(() => {
+      calcDirtyHtmlFiles = require(`../build-utils`).calcDirtyHtmlFiles
+    })
+  })
+
   function generateStateToTestHelper(
     pages: Record<
       string,
@@ -224,6 +231,71 @@ describe(`calcDirtyHtmlFiles`, () => {
     ])
   })
 
+  describe(`onCreatePage + deletePage + createPage that change path casing of a page`, () => {
+    afterAll(() => {
+      platformSpy.mockRestore()
+    })
+
+    it(`linux (case sensitive file system)`, () => {
+      let isolatedCalcDirtyHtmlFiles
+      jest.isolateModules(() => {
+        platformSpy.mockImplementation(() => `linux`)
+        isolatedCalcDirtyHtmlFiles = require(`../build-utils`)
+          .calcDirtyHtmlFiles
+      })
+
+      const state = generateStateToTestHelper({
+        // page was created, then deleted and similar page with slightly different path was created for it
+        // different artifacts would be created for them
+        "/TEST/": {
+          dirty: 0,
+          removedOrDeleted: `deleted`,
+        },
+        "/test/": {
+          dirty: 1,
+        },
+      })
+
+      const results = isolatedCalcDirtyHtmlFiles(state)
+
+      // on case sensitive file systems /test/ and /TEST/ are different files so we do need to delete a file
+      expect(results.toRegenerate.sort()).toEqual([`/test/`])
+      expect(results.toDelete.sort()).toEqual([`/TEST/`])
+      expect(Array.from(results.toCleanupFromTrackedState).sort()).toEqual([])
+    })
+
+    it(`windows / mac (case insensitive file system)`, () => {
+      let isolatedCalcDirtyHtmlFiles
+      jest.isolateModules(() => {
+        platformSpy.mockImplementation(() => `win32`)
+        isolatedCalcDirtyHtmlFiles = require(`../build-utils`)
+          .calcDirtyHtmlFiles
+      })
+
+      const state = generateStateToTestHelper({
+        // page was created, then deleted and similar page with slightly different path was created for it
+        // both page paths would result in same artifacts
+        "/TEST/": {
+          dirty: 0,
+          removedOrDeleted: `deleted`,
+        },
+        "/test/": {
+          dirty: 1,
+        },
+      })
+
+      const results = isolatedCalcDirtyHtmlFiles(state)
+
+      // on case insensitive file systems /test/ and /TEST/ are NOT different files so we should
+      // not delete files, but still we should cleanup tracked state
+      expect(results.toRegenerate.sort()).toEqual([`/test/`])
+      expect(results.toDelete.sort()).toEqual([])
+      expect(Array.from(results.toCleanupFromTrackedState).sort()).toEqual([
+        `/TEST/`,
+      ])
+    })
+  })
+
   // cases above are to be able to pinpoint exact failure, kitchen sink case is to test all of above in one go
   // and make sure that various conditions mixed together are handled correctly
   it(`kitchen sink`, () => {

packages/gatsby/src/commands/build-utils.ts

@@ -1,6 +1,6 @@
 import fs from "fs-extra"
 import path from "path"
-
+import { platform } from "os"
 import reporter from "gatsby-cli/lib/reporter"
 
 import {
@@ -66,10 +66,18 @@ export const removePageFiles = async (
   })
 }
 
+const FSisCaseInsensitive = platform() === `win32` || platform() === `darwin`
 function normalizePagePath(path: string): string {
   if (path === `/`) {
     return `/`
   }
+
+  if (FSisCaseInsensitive) {
+    // e.g. /TEST/ and /test/ would produce "same" artifacts on case insensitive
+    // file systems
+    path = path.toLowerCase()
+  }
+
   return path.endsWith(`/`) ? path.slice(0, -1) : path
 }
 
@@ -105,7 +113,8 @@ export function calcDirtyHtmlFiles(
    * to regenerate and more importantly - to delete (so we don't delete html and page-data file
    * when path changes slightly but it would still result in same html and page-data filenames
    * for example adding/removing trailing slash between builds or even mid build with plugins
-   * like `gatsby-plugin-remove-trailing-slashes`)
+   * like `gatsby-plugin-remove-trailing-slashes`). Additionally similar consideration need to
+   * be accounted for cases where page paths casing on case-insensitive file systems.
    */
   function markActionForPage(path: string, action: PageGenerationAction): void {
     const normalizedPagePath = normalizePagePath(path)