[install] Use file argument for actions, not template substitution

CMakeLists.txt

@@ -443,7 +443,7 @@ else()
   set(BAZEL_ARGS)
 endif()
 
-# N.B. If you are testing the CMake API and making changes to `install.py.in`,
+# N.B. If you are testing the CMake API and making changes to `installer.py`,
 # you can change this target to something more lightweight, such as
 # `//tools/install/dummy:install`.
 set(BAZEL_TARGETS //:install)

tools/install/BUILD.bazel

@@ -6,6 +6,7 @@ load("//tools/skylark:py.bzl", "py_library")
 load("//tools/lint:lint.bzl", "add_lint_tests")
 load(
     "@drake//tools/skylark:drake_py.bzl",
+    "drake_py_binary",
     "drake_py_unittest",
 )
 
@@ -15,16 +16,19 @@ py_library(
     srcs = ["install_test_helper.py"],
     data = ["//:install"],
     imports = ["."],
-    visibility = ["//visibility:public"],
 )
 
 exports_files(
     [
-        "install.py.in",
         "install_test.py",
     ],
 )
 
+drake_py_binary(
+    name = "installer",
+    srcs = ["installer.py"],
+)
+
 # Runs `install_test_helper` unit tests.
 drake_py_unittest(
     name = "install_test_helper_test",

tools/install/install.bzl

@@ -483,13 +483,23 @@ def _install_impl(ctx):
                  "\n  src2 = " + repr(src) +
                  "\n  dst = " + repr(a.dst))
 
+    # Generate installer manifest.
+    actions_file = ctx.actions.declare_file(ctx.attr.name + "_actions")
+    ctx.actions.write(
+        output = actions_file,
+        content = "\n".join(script_actions) + "\n",
+    )
+
     # Generate install script.
-    # TODO(mwoehlke-kitware): Figure out a better way to generate this and run
-    # it via Python than `#!/usr/bin/env python3`?
-    ctx.actions.expand_template(
-        template = ctx.executable.install_script_template,
+    ctx.actions.write(
         output = ctx.outputs.executable,
-        substitutions = {"<<actions>>": "\n    ".join(script_actions)},
+        content = "\n".join([
+            "#!/bin/bash",
+            "tools/install/installer --actions '{}' \"$@\"".format(
+                actions_file.short_path,
+            ),
+        ]),
+        is_executable = True,
     )
 
     script_tests = []
@@ -498,7 +508,7 @@ def _install_impl(ctx):
     for i in installed_tests:
         script_tests.append(i.cmd)
 
-    # Generate test installation script
+    # Generate test installation script.
     if ctx.attr.install_tests_script and not script_tests:
         fail("`install_tests_script` is not empty but no `script_tests` were provided.")  # noqa
     if ctx.attr.install_tests_script:
@@ -509,9 +519,11 @@ def _install_impl(ctx):
         )
 
     # Return actions.
-    files = ctx.runfiles(
-        files = [a.src for a in actions if not hasattr(a, "main_class")] +
-                [i.src for i in installed_tests],
+    runfiles = (
+        [a.src for a in actions if not hasattr(a, "main_class")] +
+        [i.src for i in installed_tests] +
+        ctx.files._installer +
+        [actions_file]
     )
     return [
         InstallInfo(
@@ -520,7 +532,7 @@ def _install_impl(ctx):
             installed_files = installed_files,
         ),
         InstalledTestInfo(tests = installed_tests),
-        DefaultInfo(runfiles = files),
+        DefaultInfo(runfiles = ctx.runfiles(files = runfiles)),
     ]
 
 # TODO(mwoehlke-kitware) default guess_data to PACKAGE when we have better
@@ -560,12 +572,12 @@ _install_rule = rule(
         ),
         "workspace": attr.string(),
         "allowed_externals": attr.label_list(allow_files = True),
-        "install_script_template": attr.label(
-            allow_files = True,
+        "_installer": attr.label(
             executable = True,
-            cfg = "target",
-            default = Label("//tools/install:install.py.in"),
+            cfg = "host",
+            default = Label("//tools/install:installer"),
         ),
+        "install_script": attr.output(),
         "install_tests_script": attr.output(),
     },
     executable = True,

tools/install/install.py.in → tools/install/installer.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 """
 Installation script generated from a Bazel `install` target.
 """
@@ -197,8 +196,8 @@ def fix_rpaths_and_strip():
             # dictionary to fixup other library and executable paths.
             continue
         # Enable write permissions to allow modification.
-        os.chmod(dst_full, stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR |
-                 stat.S_IRGRP | stat.S_IXGRP | stat.S_IROTH | stat.S_IXOTH)
+        os.chmod(dst_full, stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR
+                 | stat.S_IRGRP | stat.S_IXGRP | stat.S_IROTH | stat.S_IXOTH)
         if sys.platform == "darwin":
             # From the manual for BSD `strip`: for dynamic shared libraries,
             # the maximum level of stripping is usually -x (to remove all
@@ -364,8 +363,8 @@ def create_java_launcher(filename, classpath, jvm_flags, main_class):
 java {} {} "$@"
 """.format(strclasspath, jvm_flags, main_class)
         launcher_file.write(content)
-    os.chmod(filename, stat.S_IRUSR | stat.S_IRGRP | stat.S_IROTH |
-             stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH)
+    os.chmod(filename, stat.S_IRUSR | stat.S_IRGRP | stat.S_IROTH
+             | stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH)
 
 
 def main(args):
@@ -379,6 +378,9 @@ def main(args):
     # Set up options.
     parser = argparse.ArgumentParser()
     parser.add_argument('prefix', type=str, help='Install prefix')
+    parser.add_argument(
+        '--actions', type=str, required=True,
+        help='file path to installer actions')
     parser.add_argument(
         '--color', action='store_true', default=False,
         help='colorize the output')
@@ -447,7 +449,13 @@ def main(args):
             ansi_color_escape, ansi_reset_escape))
 
     # Execute the install actions.
-    <<actions>>
+    # TODO(jwnimmer-tri) Executing arbitrary Python code from the actions file
+    # is an absurd implementation choice that we've inherited from the original
+    # installer scripts.  We should rework the install.bzl <=> installer.py
+    # specification format to use something other than open-ended Python code.
+    with open(args.actions, "r", encoding="utf-8") as f:
+        actions = f.read()
+    exec(actions)
 
     # Libraries paths may need to be updated in libraries and executables.
     fix_rpaths_and_strip()

tools/install/test/install_meta_test.py

@@ -1,4 +1,4 @@
-"""Tests the behavior of targets generated from `install.py.in`."""
+"""Tests the behavior of targets that use `installer.py`."""
 
 import os
 from os.path import isdir, join, relpath