[PATCH] D152285: Add support for the NO_COLOR environment variable

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman created this revision.
aaron.ballman added reviewers: MaskRay, phosek.
Herald added a project: All.
aaron.ballman requested review of this revision.
Herald added a project: clang.

Clang currently supports disabling color diagnostic output via `-fno-color-diagnostics`. However, there is a somewhat long-standing push to support use of an environment variable to override color output so that users can set up their terminal such that most color output is disabled (largely for accessibility reasons).

There are two competing de facto standards to accomplish this: `NO_COLOR` (https://no-color.org/) and `CLICOLOR/CLICOLOR_FORCE` (http://bixense.com/clicolors/).

This patch adds support for `NO_COLOR` as that appears to be the more commonly supported feature, at least when comparing issues and pull requests:
https://github.com/search?q=NO_COLOR&type=issues (2.2k issues, 35k pull requests)
https://github.com/search?q=CLICOLOR&type=issues (1k issues, 3k pull requests)

It's also the more straightforward and thoroughly-specified of the two options. If `NO_COLOR` is present as an environment variable (regardless of value), color output is suppressed unless the command line specifies use of color output (command line takes precedence over the environment variable).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D152285

Files:
  clang/docs/ReleaseNotes.rst
  clang/docs/UsersManual.rst
  clang/lib/Frontend/CompilerInvocation.cpp
  clang/test/Driver/no-color.c


Index: clang/test/Driver/no-color.c
===================================================================
--- /dev/null
+++ clang/test/Driver/no-color.c
@@ -0,0 +1,13 @@
+// RUN: env NO_COLOR= %clang -### %s 2>&1 | FileCheck --check-prefix=NO-COLOR %s
+// RUN: env NO_COLOR= %clang -fcolor-diagnostics -### %s 2>&1 | FileCheck --check-prefix=COLOR %s
+// RUN: env NO_COLOR= %clang -fdiagnostics-color=auto -### %s 2>&1 | FileCheck --check-prefix=NO-COLOR %s
+// RUN: env NO_COLOR= %clang -fdiagnostics-color=always -### %s 2>&1 | FileCheck --check-prefix=COLOR %s
+// RUN: env NO_COLOR= %clang -fdiagnostics-color=never -### %s 2>&1 | FileCheck --check-prefix=NO-COLOR %s
+
+// Note, the value of the environment variable does not matter, only that it is defined.
+// RUN: env NO_COLOR=0 %clang -### %s 2>&1 | FileCheck --check-prefix=NO-COLOR %s
+
+int main(void) {}
+
+// COLOR: -fcolor-diagnostics
+// NO-COLOR-NOT: -fcolor-diagnostics
Index: clang/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- clang/lib/Frontend/CompilerInvocation.cpp
+++ clang/lib/Frontend/CompilerInvocation.cpp
@@ -2341,10 +2341,19 @@
   unsigned MissingArgIndex, MissingArgCount;
   InputArgList Args = getDriverOptTable().ParseArgs(
       Argv.slice(1), MissingArgIndex, MissingArgCount);
+
+  bool ShowColors = true;
+  if (std::optional<std::string> NoColor =
+          llvm::sys::Process::GetEnv("NO_COLOR")) {
+    // If the user set the NO_COLOR environment variable, we'll honor that
+    // unless the command line overrides it.
+    ShowColors = false;
+  }
+
   // We ignore MissingArgCount and the return value of ParseDiagnosticArgs.
   // Any errors that would be diagnosed here will also be diagnosed later,
   // when the DiagnosticsEngine actually exists.
-  (void)ParseDiagnosticArgs(*DiagOpts, Args);
+  (void)ParseDiagnosticArgs(*DiagOpts, Args, /*Diags=*/nullptr, ShowColors);
   return DiagOpts;
 }
 
Index: clang/docs/UsersManual.rst
===================================================================
--- clang/docs/UsersManual.rst
+++ clang/docs/UsersManual.rst
@@ -251,6 +251,11 @@
                 ^
                 //
 
+   If the ``NO_COLOR`` environment variable is defined (regardless of value),
+   color diagnostics are disabled. If ``NO_COLOR`` is defined and
+   ``-fcolor-diagnostics`` is passed on the command line, Clang will honor the
+   command line argument.
+
 .. option:: -fansi-escape-codes
 
    Controls whether ANSI escape codes are used instead of the Windows Console
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -221,6 +221,8 @@
 - Clang now support ``__builtin_FUNCSIG()`` which returns the same information
   as the ``__FUNCSIG__`` macro (available only with ``-fms-extensions`` flag).
   This fixes (`#58951 <https://github.com/llvm/llvm-project/issues/58951>`_).
+- Clang now supports the `NO_COLOR <https://no-color.org/>`_ environment
+  variable as a way to disable color diagnostics.
 
 New Compiler Flags
 ------------------


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