Add generator_bazel_env

Allows setting environment variables that affect only the nested generator call, but not the Xcode based calls. An example use case is setting `tools/bazel` output affecting env variables (e.g. color or verbosity).

Signed-off-by: Brentley Jones <github@brentleyjones.com>

Author: brentleyjones

xcodeproj/internal/xcodeproj_runner.bzl

@@ -272,6 +272,7 @@ def _write_runner(
         execution_root_file,
         extra_flags_bazelrc,
         extra_generator_flags,
+        generator_bazel_env,
         generator_build_file,
         generator_defs_bzl,
         install_path,
@@ -323,6 +324,25 @@ fi
                 ),
             ))
 
+    for key, value in generator_bazel_env.items():
+        if value == "\0":
+            collect_statements.append("""\
+if [[ -n "${{{key}:-}}" ]]; then
+  envs+=("{key}=${key}")
+fi
+""".format(key = key))
+        else:
+            base_envs_values.append("  \"{}={}\"".format(
+                key,
+                (
+                    value.replace(
+                        # Escape double quotes for bash
+                        "\"",
+                        "\\\"",
+                    )
+                ),
+            ))
+
     collect_bazel_env = """\
 envs=(
 {base_envs_values}
@@ -439,6 +459,7 @@ def _xcodeproj_runner_impl(ctx):
         extra_generator_flags = (
             ctx.attr._extra_generator_flags[BuildSettingInfo].value
         ),
+        generator_bazel_env = ctx.attr.generator_bazel_env,
         generator_build_file = generator_build_file,
         generator_defs_bzl = generator_defs_bzl,
         install_path = install_path,
@@ -474,6 +495,7 @@ xcodeproj_runner = rule(
         "config": attr.string(mandatory = True),
         "default_xcode_configuration": attr.string(),
         "focused_labels": attr.string_list(default = []),
+        "generator_bazel_env": attr.string_dict(mandatory = True),
         "generation_shard_count": attr.int(mandatory = True),
         "import_index_build_indexstores": attr.bool(mandatory = True),
         "install_directory": attr.string(mandatory = True),

xcodeproj/xcodeproj.bzl

@@ -31,6 +31,7 @@ def xcodeproj(
         default_xcode_configuration = None,
         extra_files = [],
         focused_targets = [],
+        generator_bazel_env = {},
         import_index_build_indexstores = True,
         install_directory = None,
         ios_device_cpus = "arm64",
@@ -150,6 +151,13 @@ def xcodeproj(
             listed explicitly in the `unfocused_targets` argument. The labels
             must match transitive dependencies of the targets specified in the
             `top_level_targets` argument.
+        generator_bazel_env: Optional. A `dict` of environment variables to
+            set when invoking `bazel_path` during project generation only.
+
+            This behaves the same as `bazel_env`, but only applies to the
+            generated runner's Bazel invocations while generating the project.
+            These values are not written into the generated `.xcodeproj`, and
+            they do not apply to Bazel builds launched later from Xcode.
         import_index_build_indexstores: Optional. Whether to import the index
             stores generated by Index Build.
 
@@ -365,6 +373,7 @@ def xcodeproj(
     if not bazel_path:
         bazel_path = "bazel"
     bazel_env = dict(bazel_env) if bazel_env else {}
+    generator_bazel_env = dict(generator_bazel_env) if generator_bazel_env else {}
     if "PATH" not in bazel_env:
         bazel_env["PATH"] = "/bin:/usr/bin"
     if "LANG" not in bazel_env:
@@ -391,6 +400,12 @@ def xcodeproj(
         key: "\0" if value == None else value
         for key, value in sorted(bazel_env.items())
     }
+    generator_bazel_env = {
+        # Null character is used to represent `None`, since `attr.string_dict`
+        # requires non-`None` values.
+        key: "\0" if value == None else value
+        for key, value in sorted(generator_bazel_env.items())
+    }
 
     if default_xcode_configuration and default_xcode_configuration not in xcode_configurations:
         keys = sorted(xcode_configurations.keys())
@@ -530,6 +545,7 @@ for {configuration} ({new_keys}) do not match keys of other configurations \
         config = config,
         default_xcode_configuration = default_xcode_configuration,
         focused_labels = focused_labels,
+        generator_bazel_env = generator_bazel_env,
         generation_shard_count = generation_shard_count,
         import_index_build_indexstores = import_index_build_indexstores,
         install_directory = install_directory,