[llvm-lit] Print environment variables when using env without subcommand (#98414)

This patch addresses an issue with lit's internal shell when env is
without any arguments, it fails with exit code 127 because `env`
requires a subcommand. This patch addresses the issue by encoding the
command to properly return environment variables even when no arguments
are provided.

The error occurred when running the command 
` LIT_USE_INTERNAL_SHELL=1 ninja check-llvm`.

fixes: #102383
This is part of the test cleanups proposed in the RFC: [[RFC] Enabling
the Lit Internal Shell by
Default](https://discourse.llvm.org/t/rfc-enabling-the-lit-internal-shell-by-default/80179)

Author: Harini0924

lit/TestRunner.py

@@ -742,7 +742,16 @@ def _executeShCmd(cmd, shenv, results, timeoutHelper):
                     cmd_shenv = ShellEnvironment(shenv.cwd, shenv.env)
                 args = updateEnv(cmd_shenv, args)
                 if not args:
-                    raise InternalShellError(j, "Error: 'env' requires a" " subcommand")
+                    # Return the environment variables if no argument is provided.
+                    env_str = "\n".join(
+                        f"{key}={value}" for key, value in sorted(cmd_shenv.env.items())
+                    )
+                    results.append(
+                        ShellCommandResult(
+                            j, env_str, "", 0, timeoutHelper.timeoutReached(), []
+                        )
+                    )
+                    return 0
             elif args[0] == "not":
                 not_args.append(args.pop(0))
                 not_count += 1

tests/Inputs/shtest-env/env-calls-cd.txt renamed to tests/Inputs/shtest-env-negative/env-calls-cd.txt

@@ -7,4 +7,5 @@ config.test_source_root = None
 config.test_exec_root = None
 config.environment["FOO"] = "1"
 config.environment["BAR"] = "2"
+config.environment["QUX"] = "3"
 config.substitutions.append(("%{python}", '"%s"' % (sys.executable)))

tests/Inputs/shtest-env/env-calls-colon.txt renamed to tests/Inputs/shtest-env-negative/env-calls-colon.txt

@@ -0,0 +1,32 @@
+## Tests the behaviour of chaining env commands together.
+
+## Check that internal env can call internal env.
+# RUN: env env | FileCheck -check-prefix=CHECK-2-EMPTY-ARGS %s
+#
+# CHECK-2-EMPTY-ARGS: BAR = 2
+# CHECK-2-EMPTY-ARGS: FOO = 1
+
+## Check setting variables in a nested env call.
+# RUN: env FOO=2 env BAR=1 | FileCheck -check-prefix=CHECK-2-VAL %s
+#
+# CHECK-2-VAL: BAR = 1
+# CHECK-2-VAL: FOO = 2
+
+## Check unsetting variables in a nested env call.
+# RUN: env -u FOO env -u BAR | FileCheck -check-prefix=CHECK-2-U %s
+#
+# CHECK-2-U-NOT: BAR
+# CHECK-2-U-NOT: FOO
+
+## Check mixed setting and unsetting in nested env calls.
+# RUN: env -u FOO BAR=1 env -u BAR FOO=2 | FileCheck -check-prefix=CHECK-2-U-VAL %s
+#
+# CHECK-2-U-VAL-NOT: BAR
+# CHECK-2-U-VAL: FOO = 2
+
+## Check setting, unsetting, and adding a new variable in nested env calls.
+# RUN: env -u FOO BAR=1 env -u BAR FOO=2 env BAZ=3 | FileCheck -check-prefix=CHECK-3 %s
+#
+# CHECK-3-NOT: BAR
+# CHECK-3: BAZ = 3
+# CHECK-3: FOO = 2

tests/Inputs/shtest-env/env-calls-echo.txt renamed to tests/Inputs/shtest-env-negative/env-calls-echo.txt

@@ -0,0 +1,37 @@
+## Tests the env command in various scenarios: without arguments, setting, unsetting, and mixing envrionment variables.
+
+## Check default environment.
+# RUN: env | FileCheck -check-prefix=NO-ARGS %s
+#
+# NO-ARGS: BAR=2
+# NO-ARGS: FOO=1
+# NO-ARGS: QUX=3
+
+## Set environment variables.
+# RUN: env FOO=2 BAR=1 | FileCheck -check-prefix=SET-VAL %s
+#
+# SET-VAL: BAR=1
+# SET-VAL: FOO=2
+# SET-VAL: QUX=3
+
+## Unset environment variables.
+# RUN: env -u FOO -u BAR | FileCheck -check-prefix=UNSET-U %s
+#
+# UNSET-U-NOT: BAR
+# UNSET-U-NOT: FOO
+# UNSET-U: QUX=3
+
+## Mixed set and unset environment variables.
+# RUN: env -u FOO BAR=1 -u BAR FOO=2 | FileCheck -check-prefix=MIXED-SET-UNSET %s
+#
+# MIXED-SET-UNSET-NOT: BAR
+# MIXED-SET-UNSET: FOO=2
+# MIXED-SET-UNSET: QUX=3
+
+## Mixed set and unset with additional variable.
+# RUN: env -u FOO BAR=1 -u BAR FOO=2 BAZ=4 | FileCheck -check-prefix=MIXED-SET-UNSET-ADD-3 %s
+#
+# MIXED-SET-UNSET-ADD-NOT: BAR
+# MIXED-SET-UNSET-ADD: BAZ=4
+# MIXED-SET-UNSET-ADD: FOO=2
+# MIXED-SET-UNSET-ADD: QUX=3 

tests/Inputs/shtest-env/env-calls-export.txt renamed to tests/Inputs/shtest-env-negative/env-calls-export.txt

@@ -0,0 +1,22 @@
+## Tests env command for preset variables and handling single/multiple unsets.
+
+## Check and make sure preset environment variable were set in lit.cfg.
+#
+# RUN: env | FileCheck --check-prefix=CHECK-ENV-PRESET %s
+#
+## Check single unset of environment variable.
+#
+# RUN: env -u FOO | FileCheck --check-prefix=CHECK-ENV-UNSET-1 %s
+#
+## Check multiple unsets of environment variables.
+#
+# RUN: env -u FOO -u BAR | FileCheck --check-prefix=CHECK-ENV-UNSET-MULTIPLE %s
+
+# CHECK-ENV-PRESET: BAR = 2
+# CHECK-ENV-PRESET: FOO = 1
+
+# CHECK-ENV-UNSET-1: BAR = 2
+# CHECK-ENV-UNSET-1-NOT: FOO
+
+# CHECK-ENV-UNSET-MULTIPLE-NOT: BAR
+# CHECK-ENV-UNSET-MULTIPLE-NOT: FOO

tests/Inputs/shtest-env/env-calls-mkdir.txt renamed to tests/Inputs/shtest-env-negative/env-calls-mkdir.txt

@@ -0,0 +1,15 @@
+## Tests env command for setting single and multiple environment variables.
+
+## Check for simple one environment variable setting.
+#
+# RUN: env A_FOO=999 | FileCheck --check-prefix=CHECK-ENV-1 %s
+#
+## Check for multiple environment variable settings.
+#
+# RUN: env A_FOO=1 B_BAR=2 C_OOF=3 | FileCheck --check-prefix=CHECK-ENV-MULTIPLE %s
+
+# CHECK-ENV-1: A_FOO = 999
+
+# CHECK-ENV-MULTIPLE: A_FOO = 1
+# CHECK-ENV-MULTIPLE: B_BAR = 2
+# CHECK-ENV-MULTIPLE: C_OOF = 3

tests/Inputs/shtest-env/env-calls-not-builtin.txt renamed to tests/Inputs/shtest-env-negative/env-calls-not-builtin.txt

@@ -0,0 +1,11 @@
+import lit.formats
+
+config.name = "shtest-env"
+config.suffixes = [".txt"]
+config.test_format = lit.formats.ShTest()
+config.test_source_root = None
+config.test_exec_root = None
+config.environment["FOO"] = "1"
+config.environment["BAR"] = "2"
+config.environment["QUX"] = "3"
+config.substitutions.append(("%{python}", '"%s"' % (sys.executable)))

tests/Inputs/shtest-env/env-calls-rm.txt renamed to tests/Inputs/shtest-env-negative/env-calls-rm.txt

@@ -0,0 +1,18 @@
+## Tests env command for setting and unsetting single and multiple environment variables.
+
+## Check for setting and removing one environment variable
+#
+# RUN: env A_FOO=999 -u FOO | FileCheck --check-prefix=CHECK-ENV-1 %s
+#
+## Check for setting/unsetting multiple environment variables
+#
+# RUN: env A_FOO=1 -u FOO B_BAR=2 -u BAR C_OOF=3 | FileCheck --check-prefix=CHECK-ENV-MULTIPLE %s
+
+# CHECK-ENV-1: A_FOO = 999
+# CHECK-ENV-1-NOT: FOO
+
+# CHECK-ENV-MULTIPLE: A_FOO = 1
+# CHECK-ENV-MULTIPLE-NOT: BAR
+# CHECK-ENV-MULTIPLE: B_BAR = 2
+# CHECK-ENV-MULTIPLE: C_OOF = 3
+# CHECK-ENV-MULTIPLE-NOT: FOO

tests/Inputs/shtest-env/lit.cfg renamed to tests/Inputs/shtest-env-negative/lit.cfg

@@ -0,0 +1,49 @@
+## Test the env command (failing tests).
+
+# RUN: not %{lit} -a -v %{inputs}/shtest-env-negative \
+# RUN: | FileCheck -match-full-lines %s
+#
+# END.
+
+## Test the env command's expected failures.
+
+# CHECK: -- Testing: 7 tests{{.*}}
+
+# CHECK: FAIL: shtest-env :: env-calls-cd.txt ({{[^)]*}})
+# CHECK: env -u FOO BAR=3 cd foobar
+# CHECK: # executed command: env -u FOO BAR=3 cd foobar
+# CHECK: # error: command failed with exit status: {{.*}}
+
+# CHECK: FAIL: shtest-env :: env-calls-colon.txt ({{[^)]*}})
+# CHECK: env -u FOO BAR=3 :
+# CHECK: # executed command: env -u FOO BAR=3 :
+# CHECK: # error: command failed with exit status: {{.*}}
+
+# CHECK: FAIL: shtest-env :: env-calls-echo.txt ({{[^)]*}})
+# CHECK: env -u FOO BAR=3 echo hello world
+# CHECK: # executed command: env -u FOO BAR=3 echo hello world
+# CHECK: # error: command failed with exit status: {{.*}}
+
+# CHECK: FAIL: shtest-env :: env-calls-export.txt ({{[^)]*}})
+# CHECK: env -u FOO BAR=3 export BAZ=3
+# CHECK: # executed command: env -u FOO BAR=3 export BAZ=3
+# CHECK: # error: command failed with exit status: {{.*}}
+
+# CHECK: FAIL: shtest-env :: env-calls-mkdir.txt ({{[^)]*}})
+# CHECK: env -u FOO BAR=3 mkdir foobar
+# CHECK: # executed command: env -u FOO BAR=3 mkdir foobar
+# CHECK: # error: command failed with exit status: {{.*}}
+
+# CHECK: FAIL: shtest-env :: env-calls-not-builtin.txt ({{[^)]*}})
+# CHECK: env -u FOO BAR=3 not rm {{.+}}.no-such-file
+# CHECK: # executed command: env -u FOO BAR=3 not rm {{.+}}.no-such-file{{.*}}
+# CHECK: # error: command failed with exit status: {{.*}}
+
+# CHECK: FAIL: shtest-env :: env-calls-rm.txt ({{[^)]*}})
+# CHECK: env -u FOO BAR=3 rm foobar
+# CHECK: # executed command: env -u FOO BAR=3 rm foobar
+# CHECK: # error: command failed with exit status: {{.*}}
+
+# CHECK: Total Discovered Tests: 7
+# CHECK: Failed: 7 {{\([0-9]*\.[0-9]*%\)}}
+# CHECK-NOT: {{.}}

tests/Inputs/shtest-env/env-args-last-is-assign.txt renamed to tests/Inputs/shtest-env-positive/env-args-last-is-assign.txt

@@ -0,0 +1,70 @@
+## Test the env command (passing tests).
+
+# RUN: %{lit} -a -v %{inputs}/shtest-env-positive \
+# RUN: | FileCheck -match-full-lines %s
+#
+# END.
+
+## Test the env command's successful executions.
+
+# CHECK: -- Testing: 9 tests{{.*}}
+
+# CHECK: PASS: shtest-env :: env-args-last-is-assign.txt ({{[^)]*}})
+# CHECK: env FOO=1
+# CHECK: # executed command: env FOO=1
+# CHECK-NOT: # error:
+# CHECK: --
+
+# CHECK: PASS: shtest-env :: env-args-last-is-u-arg.txt ({{[^)]*}})
+# CHECK: env -u FOO
+# CHECK: # executed command: env -u FOO
+# CHECK-NOT: # error:
+# CHECK: --
+
+# CHECK: PASS: shtest-env :: env-args-last-is-u.txt ({{[^)]*}})
+# CHECK: env -u
+# CHECK: # executed command: env -u
+# CHECK-NOT: # error:
+# CHECK: --
+
+# CHECK: PASS: shtest-env :: env-args-nested-none.txt ({{[^)]*}})
+# CHECK: env env env
+# CHECK: # executed command: env env env
+# CHECK-NOT: # error:
+# CHECK: --
+
+# CHECK: PASS: shtest-env :: env-calls-env.txt ({{[^)]*}})
+# CHECK: env env | {{.*}}
+# CHECK: # executed command: env env
+# CHECK-NOT: # error:
+# CHECK: --
+
+# CHECK: PASS: shtest-env :: env-no-subcommand.txt ({{[^)]*}})
+# CHECK: env | {{.*}}
+# CHECK: # executed command: env
+# CHECK: env FOO=2 BAR=1 | {{.*}}
+# CHECK: # executed command: env FOO=2 BAR=1
+# CHECK-NOT: # error:
+# CHECK: --
+
+# CHECK: PASS: shtest-env :: env-u.txt ({{[^)]*}})
+# CHECK: env -u FOO | {{.*}}
+# CHECK: # executed command: env -u FOO
+# CHECK-NOT: # error:
+# CHECK: --
+
+# CHECK: PASS: shtest-env :: env.txt ({{[^)]*}})
+# CHECK: env A_FOO=999 | {{.*}}
+# CHECK: # executed command: env A_FOO=999
+# CHECK-NOT: # error:
+# CHECK: --
+
+# CHECK: PASS: shtest-env :: mixed.txt ({{[^)]*}})
+# CHECK: env A_FOO=999 -u FOO | {{.*}}
+# CHECK: # executed command: env A_FOO=999 -u FOO
+# CHECK-NOT: # error:
+# CHECK: --
+
+# CHECK: Total Discovered Tests: 9
+# CHECK: Passed: 9 {{\([0-9]*\.[0-9]*%\)}}
+# CHECK-NOT: {{.}}