fix: `--env` flag confusing message on syntax error (#23915)

Enhanced warning message for --env flag with run and eval subcommands. 

The commit is specifically made to address issue #23674 by improving the
warning messages that appear when using the --env flag with run or eval
subcommands in the following scenarios:

1. Missing environment file.
2. Incorrect syntax in the environment file content.


**Changes made**

- Distinguishes between cases of missing environment file and wrong
syntax in the environment file content.
- Shows a concise warning message to convey the case/issue occurred.

**Code changes & enhancements**
- Implemented a match statement to handle different types of errors
received while getting and parsing the file content to display a concise
warning message, rather than simple error check and then displaying the
same warning message for whatever the type of error is.
- Updated the related existing tests to reflect the new warning
messages.
- Added two test cases to cover the wrong environment file content
syntax with both run and eval subcommands.

**Impact**
The use of --env flag with both run/eval would be more user-friendly as
it gives a precise description of what is not right when using
incorrectly.

If you could give it a look, @dsherret , I appreciate your feedback on
these changes.

---------

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

8 files changed, 23 insertions, 2 deletions

diff --git a/tests/specs/eval/env_unparsable_file/__test__.jsonc b/tests/specs/eval/env_unparsable_file/__test__.jsonc
new file mode 100644
index 000000000..cf5e9a99b
--- /dev/null
+++ b/tests/specs/eval/env_unparsable_file/__test__.jsonc
@@ -0,0 +1,4 @@
+{
+  "args": "eval --env=../../../testdata/env_unparsable console.log(Deno.env.get(\"Another_FOO\"))",
+  "output": "main.out"
+}
diff --git a/tests/specs/eval/env_unparsable_file/main.out b/tests/specs/eval/env_unparsable_file/main.out
new file mode 100644
index 000000000..18d7856b4
--- /dev/null
+++ b/tests/specs/eval/env_unparsable_file/main.out
@@ -0,0 +1,2 @@
+Warning Parsing failed within the specified environment file: ../../../testdata/env_unparsable at index: 3 of the value: c:\path
+undefined
diff --git a/tests/specs/run/env_unparsable_file/__test__.jsonc b/tests/specs/run/env_unparsable_file/__test__.jsonc
new file mode 100644
index 000000000..bed150635
--- /dev/null
+++ b/tests/specs/run/env_unparsable_file/__test__.jsonc
@@ -0,0 +1,4 @@
+{
+  "args": "run --env=../../../testdata/env_unparsable --allow-env main.js",
+  "output": "main.out"
+}
diff --git a/tests/specs/run/env_unparsable_file/main.js b/tests/specs/run/env_unparsable_file/main.js
new file mode 100644
index 000000000..48488ce72
--- /dev/null
+++ b/tests/specs/run/env_unparsable_file/main.js
@@ -0,0 +1,3 @@
+console.log(Deno.env.get("FOO"));
+console.log(Deno.env.get("ANOTHER_FOO"));
+console.log(Deno.env.get("MULTILINE"));
diff --git a/tests/specs/run/env_unparsable_file/main.out b/tests/specs/run/env_unparsable_file/main.out
new file mode 100644
index 000000000..a19ff4dd6
--- /dev/null
+++ b/tests/specs/run/env_unparsable_file/main.out
@@ -0,0 +1,4 @@
+Warning Parsing failed within the specified environment file: ../../../testdata/env_unparsable at index: 3 of the value: c:\path
+valid
+undefined
+undefined
diff --git a/tests/testdata/env_unparsable b/tests/testdata/env_unparsable
new file mode 100644
index 000000000..5542b80bc
--- /dev/null
+++ b/tests/testdata/env_unparsable
@@ -0,0 +1,4 @@
+FOO=valid
+ANOTHER_FOO=c:\path
+MULTILINE="First Line
+Second Line"
\ No newline at end of file
diff --git a/tests/testdata/eval/env_file_missing.out b/tests/testdata/eval/env_file_missing.out
index 221acab93..2ec371438 100644
--- a/tests/testdata/eval/env_file_missing.out
+++ b/tests/testdata/eval/env_file_missing.out
@@ -1,2 +1,2 @@
-Warning The `--env` flag was used, but the dotenv file 'missing' was not found.
+Warning The `--env` flag was used, but the environment file specified 'missing' was not found.
 undefined
diff --git a/tests/testdata/run/env_file_missing.out b/tests/testdata/run/env_file_missing.out
index ae1f8f595..6ec9b298f 100644
--- a/tests/testdata/run/env_file_missing.out
+++ b/tests/testdata/run/env_file_missing.out
@@ -1,4 +1,4 @@
-Warning The `--env` flag was used, but the dotenv file 'missing' was not found.
+Warning The `--env` flag was used, but the environment file specified 'missing' was not found.
 undefined
 undefined
 undefined