Add a bot to verify that generated SKSL files have not been hand-edited

Bug: skia:6893
Change-Id: I54480ddd1ad1989661393500044f9164a99ce7b0
Reviewed-on: https://skia-review.googlesource.com/27700
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Eric Boren <borenet@google.com>

9 files changed, 635 insertions, 4 deletions

diff --git a/infra/bots/gen_tasks.go b/infra/bots/gen_tasks.go
index 1d84615bee..7d03526dae 100644
--- a/infra/bots/gen_tasks.go
+++ b/infra/bots/gen_tasks.go
@@ -588,6 +588,29 @@ func ctSKPs(b *specs.TasksCfgBuilder, name string) string {
 	return name
 }
 
+// checkGeneratedFiles verifies that no generated SKSL files have been edited
+// by hand.
+func checkGeneratedFiles(b *specs.TasksCfgBuilder, name string) string {
+	b.MustAddTask(name, &specs.TaskSpec{
+		CipdPackages: []*specs.CipdPackage{},
+		Dimensions:   linuxGceDimensions(),
+		ExtraArgs: []string{
+			"--workdir", "../../..", "check_generated_files",
+			fmt.Sprintf("repository=%s", specs.PLACEHOLDER_REPO),
+			fmt.Sprintf("buildername=%s", name),
+			fmt.Sprintf("swarm_out_dir=%s", specs.PLACEHOLDER_ISOLATED_OUTDIR),
+			fmt.Sprintf("revision=%s", specs.PLACEHOLDER_REVISION),
+			fmt.Sprintf("patch_repo=%s", specs.PLACEHOLDER_PATCH_REPO),
+			fmt.Sprintf("patch_storage=%s", specs.PLACEHOLDER_PATCH_STORAGE),
+			fmt.Sprintf("patch_issue=%s", specs.PLACEHOLDER_ISSUE),
+			fmt.Sprintf("patch_set=%s", specs.PLACEHOLDER_PATCHSET),
+		},
+		Isolate:  relpath("compile_skia.isolate"),
+		Priority: 0.8,
+	})
+	return name
+}
+
 // housekeeper generates a Housekeeper task. Returns the name of the last task
 // in the generated chain of tasks, which the Job should add as a dependency.
 func housekeeper(b *specs.TasksCfgBuilder, name, compileTaskName string) string {
@@ -868,6 +891,7 @@ func process(b *specs.TasksCfgBuilder, name string) {
 	if parts["role"] != "Build" &&
 		name != "Housekeeper-PerCommit-BundleRecipes" &&
 		name != "Housekeeper-PerCommit-InfraTests" &&
+		name != "Housekeeper-PerCommit-CheckGeneratedFiles" &&
 		!strings.Contains(name, "RecreateSKPs") &&
 		!strings.Contains(name, "UpdateMetaConfig") &&
 		!strings.Contains(name, "-CT_") &&
@@ -875,10 +899,13 @@ func process(b *specs.TasksCfgBuilder, name string) {
 		compile(b, compileTaskName, compileTaskParts)
 	}
 
-	// Housekeeper.
+	// Housekeepers.
 	if name == "Housekeeper-PerCommit" {
 		deps = append(deps, housekeeper(b, name, compileTaskName))
 	}
+	if name == "Housekeeper-PerCommit-CheckGeneratedFiles" {
+		deps = append(deps, checkGeneratedFiles(b, name))
+	}
 
 	// Common assets needed by the remaining bots.
 
diff --git a/infra/bots/jobs.json b/infra/bots/jobs.json
index f41367ef5b..9501fc3638 100644
--- a/infra/bots/jobs.json
+++ b/infra/bots/jobs.json
@@ -77,6 +77,7 @@
   "Housekeeper-Nightly-UpdateMetaConfig",
   "Housekeeper-PerCommit",
   "Housekeeper-PerCommit-BundleRecipes",
+  "Housekeeper-PerCommit-CheckGeneratedFiles",
   "Housekeeper-PerCommit-InfraTests",
   "Housekeeper-PerCommit-IsolateSKP",
   "Housekeeper-PerCommit-IsolateSVG",
diff --git a/infra/bots/recipe_modules/flavor/examples/full.expected/Housekeeper-PerCommit-CheckGeneratedFiles.json b/infra/bots/recipe_modules/flavor/examples/full.expected/Housekeeper-PerCommit-CheckGeneratedFiles.json
new file mode 100644
index 0000000000..bbcd966d68
--- /dev/null
+++ b/infra/bots/recipe_modules/flavor/examples/full.expected/Housekeeper-PerCommit-CheckGeneratedFiles.json
@@ -0,0 +1,223 @@
+[
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "[CUSTOM_/_B_WORK]/skia/bin/fetch-gn"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/skia",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "infra_step": true,
+    "name": "fetch-gn"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "[CUSTOM_/_B_WORK]/skia/bin/fetch-clang-format"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/skia",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "infra_step": true,
+    "name": "fetch-clang-format"
+  },
+  {
+    "cmd": [
+      "[CUSTOM_/_B_WORK]/skia/bin/gn",
+      "gen",
+      "[START_DIR]/out/Release",
+      "--args=is_debug=false skia_compile_processors=true"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/skia",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "[CUSTOM_/_B_WORK]/skia/bin:<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "name": "gn gen"
+  },
+  {
+    "cmd": [
+      "ninja",
+      "-C",
+      "[START_DIR]/out/Release"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/skia",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "[CUSTOM_/_B_WORK]/skia/bin:<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "name": "ninja"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "rmtree",
+      "results_dir"
+    ],
+    "infra_step": true,
+    "name": "rmtree results_dir"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "ensure-directory",
+      "--mode",
+      "0777",
+      "results_dir"
+    ],
+    "infra_step": true,
+    "name": "makedirs results_dir"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "rmtree",
+      "device_results_dir"
+    ],
+    "infra_step": true,
+    "name": "rmtree device_results_dir"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "ensure-directory",
+      "--mode",
+      "0777",
+      "device_results_dir"
+    ],
+    "infra_step": true,
+    "name": "makedirs device_results_dir"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "copy",
+      "[CUSTOM_/_B_WORK]/skia/infra/bots/assets/skp/VERSION",
+      "/path/to/tmp/"
+    ],
+    "infra_step": true,
+    "name": "Get downloaded SKP VERSION"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "copy",
+      "42",
+      "[START_DIR]/tmp/SKP_VERSION"
+    ],
+    "infra_step": true,
+    "name": "write SKP_VERSION"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "copy",
+      "[CUSTOM_/_B_WORK]/skia/infra/bots/assets/skimage/VERSION",
+      "/path/to/tmp/"
+    ],
+    "infra_step": true,
+    "name": "Get downloaded skimage VERSION"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "copy",
+      "42",
+      "[START_DIR]/tmp/SK_IMAGE_VERSION"
+    ],
+    "infra_step": true,
+    "name": "write SK_IMAGE_VERSION"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "copy",
+      "[CUSTOM_/_B_WORK]/skia/infra/bots/assets/svg/VERSION",
+      "/path/to/tmp/"
+    ],
+    "infra_step": true,
+    "name": "Get downloaded SVG VERSION"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "copy",
+      "42",
+      "[START_DIR]/tmp/SVG_VERSION"
+    ],
+    "infra_step": true,
+    "name": "write SVG_VERSION"
+  },
+  {
+    "cmd": [
+      "[START_DIR]/out/Release/dm",
+      "--some-flag"
+    ],
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "name": "dm"
+  },
+  {
+    "name": "$result",
+    "recipe_result": null,
+    "status_code": 0
+  }
+]
\ No newline at end of file
diff --git a/infra/bots/recipe_modules/flavor/examples/full.py b/infra/bots/recipe_modules/flavor/examples/full.py
index f7d0ae5587..26775be4b8 100644
--- a/infra/bots/recipe_modules/flavor/examples/full.py
+++ b/infra/bots/recipe_modules/flavor/examples/full.py
@@ -72,6 +72,7 @@ TEST_BUILDERS = [
   'Build-Win-MSVC-x86_64-Debug-NoGPU',
   'Build-Win-MSVC-x86_64-Release-Exceptions',
   'Build-Win-MSVC-x86_64-Release-Vulkan',
+  'Housekeeper-PerCommit-CheckGeneratedFiles',
   'Perf-Android-Clang-NexusPlayer-GPU-PowerVR-x86-Debug-Android',
   'Perf-ChromeOS-Clang-Chromebook_513C24_K01-GPU-MaliT860-arm-Release',
   'Perf-Chromecast-GCC-Chorizo-CPU-Cortex_A7-arm-Release',
diff --git a/infra/bots/recipe_modules/flavor/gn_flavor.py b/infra/bots/recipe_modules/flavor/gn_flavor.py
index f02f2be962..3b81255168 100644
--- a/infra/bots/recipe_modules/flavor/gn_flavor.py
+++ b/infra/bots/recipe_modules/flavor/gn_flavor.py
@@ -105,6 +105,8 @@ class GNFlavorUtils(default_flavor.DefaultFlavorUtils):
         args['skia_vulkan_sdk'] = '"%s"' % linux_vulkan_sdk
       if 'Win' in os:
         args['skia_vulkan_sdk'] = '"%s"' % win_vulkan_sdk
+    if 'CheckGeneratedFiles' in extra_config:
+      args['skia_compile_processors'] = 'true'
 
     for (k,v) in {
       'cc':  cc,
@@ -129,8 +131,16 @@ class GNFlavorUtils(default_flavor.DefaultFlavorUtils):
 
     with self.m.context(cwd=self.m.vars.skia_dir):
       self._py('fetch-gn', self.m.vars.skia_dir.join('bin', 'fetch-gn'))
-      self._run('gn gen', [gn, 'gen', self.out_dir, '--args=' + gn_args])
-      self._run('ninja', [ninja, '-C', self.out_dir])
+      env = {}
+      if 'CheckGeneratedFiles' in extra_config:
+        env['PATH'] = '%s:%%(PATH)s' % self.m.vars.skia_dir.join('bin')
+        self._py(
+            'fetch-clang-format',
+            self.m.vars.skia_dir.join('bin', 'fetch-clang-format'))
+
+      with self.m.env(env):
+        self._run('gn gen', [gn, 'gen', self.out_dir, '--args=' + gn_args])
+        self._run('ninja', [ninja, '-C', self.out_dir])
 
   def copy_extra_build_products(self, swarming_out_dir):
     configuration = self.m.vars.builder_cfg.get('configuration', '')
diff --git a/infra/bots/recipe_modules/vars/api.py b/infra/bots/recipe_modules/vars/api.py
index da11651802..b5f39834f4 100644
--- a/infra/bots/recipe_modules/vars/api.py
+++ b/infra/bots/recipe_modules/vars/api.py
@@ -44,7 +44,8 @@ class SkiaVarsApi(recipe_api.RecipeApi):
                                 '-CT_' in self.builder_name or
                                 'Presubmit' in self.builder_name or
                                 'InfraTests' in self.builder_name or
-                                self.builder_name == "Housekeeper-PerCommit")
+                                self.builder_name == "Housekeeper-PerCommit" or
+                                'CheckGeneratedFiles' in self.builder_name)
     if self.persistent_checkout:
       if 'Win' in self.builder_name:
         self.checkout_root = self.make_path('C:\\', 'b', 'work')
diff --git a/infra/bots/recipes/check_generated_files.expected/Housekeeper-PerCommit-CheckGeneratedFiles.json b/infra/bots/recipes/check_generated_files.expected/Housekeeper-PerCommit-CheckGeneratedFiles.json
new file mode 100644
index 0000000000..afd93821a0
--- /dev/null
+++ b/infra/bots/recipes/check_generated_files.expected/Housekeeper-PerCommit-CheckGeneratedFiles.json
@@ -0,0 +1,253 @@
+[
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "ensure-directory",
+      "--mode",
+      "0777",
+      "[CUSTOM_/_B_WORK]"
+    ],
+    "infra_step": true,
+    "name": "makedirs checkout_path"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "remove",
+      "[CUSTOM_/_B_WORK]/.gclient_entries"
+    ],
+    "infra_step": true,
+    "name": "remove [CUSTOM_/_B_WORK]/.gclient_entries"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
+      "--spec",
+      "cache_dir = '[CUSTOM_/_B_CACHE]'\nsolutions = [{'deps_file': '.DEPS.git', 'managed': False, 'name': 'skia', 'url': 'https://skia.googlesource.com/skia.git'}]",
+      "--patch_root",
+      "skia",
+      "--revision_mapping_file",
+      "{\"got_revision\": \"skia\"}",
+      "--git-cache-dir",
+      "[CUSTOM_/_B_CACHE]",
+      "--cleanup-dir",
+      "[CLEANUP]/bot_update",
+      "--output_json",
+      "/path/to/tmp/json",
+      "--revision",
+      "skia@abc123"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]",
+    "env": {
+      "GIT_HTTP_LOW_SPEED_LIMIT": "1000",
+      "GIT_HTTP_LOW_SPEED_TIME": "300",
+      "PATH": "<PATH>:RECIPE_PACKAGE_REPO[depot_tools]"
+    },
+    "infra_step": true,
+    "name": "bot_update",
+    "~followup_annotations": [
+      "@@@STEP_TEXT@Some step text@@@",
+      "@@@STEP_LOG_LINE@json.output@{@@@",
+      "@@@STEP_LOG_LINE@json.output@  \"did_run\": true, @@@",
+      "@@@STEP_LOG_LINE@json.output@  \"fixed_revisions\": {@@@",
+      "@@@STEP_LOG_LINE@json.output@    \"skia\": \"abc123\"@@@",
+      "@@@STEP_LOG_LINE@json.output@  }, @@@",
+      "@@@STEP_LOG_LINE@json.output@  \"manifest\": {@@@",
+      "@@@STEP_LOG_LINE@json.output@    \"skia\": {@@@",
+      "@@@STEP_LOG_LINE@json.output@      \"repository\": \"https://fake.org/skia.git\", @@@",
+      "@@@STEP_LOG_LINE@json.output@      \"revision\": \"9046e2e693bb92a76e972b694580e5d17ad10748\"@@@",
+      "@@@STEP_LOG_LINE@json.output@    }@@@",
+      "@@@STEP_LOG_LINE@json.output@  }, @@@",
+      "@@@STEP_LOG_LINE@json.output@  \"patch_failure\": false, @@@",
+      "@@@STEP_LOG_LINE@json.output@  \"patch_root\": \"skia\", @@@",
+      "@@@STEP_LOG_LINE@json.output@  \"properties\": {@@@",
+      "@@@STEP_LOG_LINE@json.output@    \"got_revision\": \"9046e2e693bb92a76e972b694580e5d17ad10748\", @@@",
+      "@@@STEP_LOG_LINE@json.output@    \"got_revision_cp\": \"refs/heads/master@{#164710}\"@@@",
+      "@@@STEP_LOG_LINE@json.output@  }, @@@",
+      "@@@STEP_LOG_LINE@json.output@  \"root\": \"skia\", @@@",
+      "@@@STEP_LOG_LINE@json.output@  \"step_text\": \"Some step text\"@@@",
+      "@@@STEP_LOG_LINE@json.output@}@@@",
+      "@@@STEP_LOG_END@json.output@@@",
+      "@@@SET_BUILD_PROPERTY@got_revision@\"9046e2e693bb92a76e972b694580e5d17ad10748\"@@@",
+      "@@@SET_BUILD_PROPERTY@got_revision_cp@\"refs/heads/master@{#164710}\"@@@"
+    ]
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[recipe_engine::file]/resources/fileutil.py",
+      "--json-output",
+      "/path/to/tmp/json",
+      "ensure-directory",
+      "--mode",
+      "0777",
+      "[START_DIR]/tmp"
+    ],
+    "infra_step": true,
+    "name": "makedirs tmp_dir"
+  },
+  {
+    "cmd": [
+      "git",
+      "diff",
+      "--no-ext-diff"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/skia",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "name": "git diff #1",
+    "stdout": "/path/to/tmp/"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "import os\nimport subprocess\n\nfor r, d, files in os.walk('[CUSTOM_/_B_WORK]/skia'):\n  for f in files:\n    if f.endswith('.fp'):\n      path = os.path.join(r, f)\n      print 'touch %s' % path\n      subprocess.check_call(['touch', path])\n"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/skia",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "name": "touch fp files",
+    "~followup_annotations": [
+      "@@@STEP_LOG_LINE@python.inline@import os@@@",
+      "@@@STEP_LOG_LINE@python.inline@import subprocess@@@",
+      "@@@STEP_LOG_LINE@python.inline@@@@",
+      "@@@STEP_LOG_LINE@python.inline@for r, d, files in os.walk('[CUSTOM_/_B_WORK]/skia'):@@@",
+      "@@@STEP_LOG_LINE@python.inline@  for f in files:@@@",
+      "@@@STEP_LOG_LINE@python.inline@    if f.endswith('.fp'):@@@",
+      "@@@STEP_LOG_LINE@python.inline@      path = os.path.join(r, f)@@@",
+      "@@@STEP_LOG_LINE@python.inline@      print 'touch %s' % path@@@",
+      "@@@STEP_LOG_LINE@python.inline@      subprocess.check_call(['touch', path])@@@",
+      "@@@STEP_LOG_END@python.inline@@@"
+    ]
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "[CUSTOM_/_B_WORK]/skia/bin/fetch-gn"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/skia",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "infra_step": true,
+    "name": "fetch-gn"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "[CUSTOM_/_B_WORK]/skia/bin/fetch-clang-format"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/skia",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "infra_step": true,
+    "name": "fetch-clang-format"
+  },
+  {
+    "cmd": [
+      "[CUSTOM_/_B_WORK]/skia/bin/gn",
+      "gen",
+      "[START_DIR]/out/Release",
+      "--args=is_debug=false skia_compile_processors=true"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/skia",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "[CUSTOM_/_B_WORK]/skia/bin:<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "name": "gn gen"
+  },
+  {
+    "cmd": [
+      "ninja",
+      "-C",
+      "[START_DIR]/out/Release"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/skia",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "[CUSTOM_/_B_WORK]/skia/bin:<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "name": "ninja"
+  },
+  {
+    "cmd": [
+      "git",
+      "diff",
+      "--no-ext-diff"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/skia",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "name": "git diff #2",
+    "stdout": "/path/to/tmp/"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "\ndiff1 = ''''''\n\ndiff2 = ''''''\n\nif diff1 != diff2:\n  print 'Generated files have been edited!'\n  exit(1)\n"
+    ],
+    "cwd": "[CUSTOM_/_B_WORK]/skia",
+    "env": {
+      "BUILDTYPE": "Release",
+      "CHROME_HEADLESS": "1",
+      "PATH": "<PATH>:RECIPE_PACKAGE_REPO[depot_tools]",
+      "SKIA_OUT": "[START_DIR]/out"
+    },
+    "name": "compare diffs",
+    "~followup_annotations": [
+      "@@@STEP_LOG_LINE@python.inline@@@@",
+      "@@@STEP_LOG_LINE@python.inline@diff1 = ''''''@@@",
+      "@@@STEP_LOG_LINE@python.inline@@@@",
+      "@@@STEP_LOG_LINE@python.inline@diff2 = ''''''@@@",
+      "@@@STEP_LOG_LINE@python.inline@@@@",
+      "@@@STEP_LOG_LINE@python.inline@if diff1 != diff2:@@@",
+      "@@@STEP_LOG_LINE@python.inline@  print 'Generated files have been edited!'@@@",
+      "@@@STEP_LOG_LINE@python.inline@  exit(1)@@@",
+      "@@@STEP_LOG_END@python.inline@@@"
+    ]
+  },
+  {
+    "name": "$result",
+    "recipe_result": null,
+    "status_code": 0
+  }
+]
\ No newline at end of file
diff --git a/infra/bots/recipes/check_generated_files.py b/infra/bots/recipes/check_generated_files.py
new file mode 100644
index 0000000000..fc4f79b02a
--- /dev/null
+++ b/infra/bots/recipes/check_generated_files.py
@@ -0,0 +1,86 @@
+# Copyright 2017 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+
+# Recipe for the Skia PerCommit Housekeeper.
+
+DEPS = [
+  'recipe_engine/context',
+  'recipe_engine/path',
+  'recipe_engine/properties',
+  'recipe_engine/python',
+  'recipe_engine/raw_io',
+  'recipe_engine/step',
+  'core',
+  'flavor',
+  'run',
+  'vars',
+]
+
+
+def RunSteps(api):
+  # Checkout, compile, etc.
+  api.core.setup()
+
+  cwd = api.path['checkout']
+
+  with api.context(cwd=cwd):
+    # Get a baseline diff. This should be empty, but we want to be flexible for
+    # cases where we have local diffs on purpose.
+    diff1 = api.run(
+        api.step,
+        'git diff #1',
+        cmd=['git', 'diff', '--no-ext-diff'],
+        stdout=api.m.raw_io.output()).stdout
+
+    # Touch all .fp files so that the generated files are rebuilt.
+    api.run(
+        api.python.inline,
+        'touch fp files',
+        program="""import os
+import subprocess
+
+for r, d, files in os.walk('%s'):
+  for f in files:
+    if f.endswith('.fp'):
+      path = os.path.join(r, f)
+      print 'touch %%s' %% path
+      subprocess.check_call(['touch', path])
+""" % cwd)
+
+    # Regenerate the SKSL files.
+    api.flavor.compile('compile_processors')
+
+    # Get a second diff. If this doesn't match the first, then there have been
+    # modifications to the generated files.
+    diff2 = api.run(
+        api.step,
+        'git diff #2',
+        cmd=['git', 'diff', '--no-ext-diff'],
+        stdout=api.m.raw_io.output()).stdout
+
+    api.run(
+        api.python.inline,
+        'compare diffs',
+        program="""
+diff1 = '''%s'''
+
+diff2 = '''%s'''
+
+if diff1 != diff2:
+  print 'Generated files have been edited!'
+  exit(1)
+""" % (diff1, diff2))
+
+
+def GenTests(api):
+  yield (
+      api.test('Housekeeper-PerCommit-CheckGeneratedFiles') +
+      api.properties(buildername='Housekeeper-PerCommit-CheckGeneratedFiles',
+                     repository='https://skia.googlesource.com/skia.git',
+                     revision='abc123',
+                     path_config='kitchen',
+                     swarm_out_dir='[SWARM_OUT_DIR]') +
+      api.path.exists(api.path['start_dir'])
+  )
diff --git a/infra/bots/tasks.json b/infra/bots/tasks.json
index 4643563e27..34cdea7c77 100644
--- a/infra/bots/tasks.json
+++ b/infra/bots/tasks.json
@@ -470,6 +470,12 @@
         "Housekeeper-PerCommit-BundleRecipes"
       ]
     },
+    "Housekeeper-PerCommit-CheckGeneratedFiles": {
+      "priority": 0.8,
+      "tasks": [
+        "Housekeeper-PerCommit-CheckGeneratedFiles"
+      ]
+    },
     "Housekeeper-PerCommit-InfraTests": {
       "priority": 0.8,
       "tasks": [
@@ -4504,6 +4510,29 @@
       "isolate": "bundle_recipes.isolate",
       "priority": 0.7
     },
+    "Housekeeper-PerCommit-CheckGeneratedFiles": {
+      "dimensions": [
+        "cpu:x86-64-avx2",
+        "gpu:none",
+        "os:Debian-9.0",
+        "pool:Skia"
+      ],
+      "extra_args": [
+        "--workdir",
+        "../../..",
+        "check_generated_files",
+        "repository=<(REPO)",
+        "buildername=Housekeeper-PerCommit-CheckGeneratedFiles",
+        "swarm_out_dir=${ISOLATED_OUTDIR}",
+        "revision=<(REVISION)",
+        "patch_repo=<(PATCH_REPO)",
+        "patch_storage=<(PATCH_STORAGE)",
+        "patch_issue=<(ISSUE)",
+        "patch_set=<(PATCHSET)"
+      ],
+      "isolate": "compile_skia.isolate",
+      "priority": 0.8
+    },
     "Housekeeper-PerCommit-InfraTests": {
       "cipd_packages": [
         {