From 23742e237a114eb28d605257b936c54087dbb180 Mon Sep 17 00:00:00 2001
From: Dmitry Sharabin <dmitrysharabin@gmail.com>
Date: Thu, 18 Dec 2025 16:52:41 +0100
Subject: [PATCH 01/11] First pass on adding the Dotenv language

---
 src/languages/dotenv.js | 102 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 src/languages/dotenv.js

diff --git a/src/languages/dotenv.js b/src/languages/dotenv.js
new file mode 100644
index 0000000000..7d0c90ae8b
--- /dev/null
+++ b/src/languages/dotenv.js
@@ -0,0 +1,102 @@
+/** @type {LanguageProto<'dotenv'>} */
+export default {
+	id: 'dotenv',
+	optional: 'bash',
+	grammar () {
+		/**
+		 * @param {RegExp} prefix
+		 * @returns {Array<GrammarToken>}
+		 */
+		const commonPatterns = prefix => {
+			return [
+				{
+					pattern: RegExp(
+						prefix.source +
+							/(?:-?[1-9]\d*|0)(?:\\.\d+)?(?=\s*\}|\s[^}]+$|\s*$|"$)/.source
+					),
+					alias: 'number',
+				},
+				{
+					pattern: RegExp(prefix.source + /(?:false|true)(?=\s*\}|\s[^}]+$|\s*$)/.source),
+					alias: 'boolean',
+				},
+				{
+					// Ignore leading and trailing whitespace characters
+					pattern: RegExp(prefix.source + /(\S[^}]*?\S)(?=\s*\})/.source),
+					alias: 'string',
+				},
+			];
+		};
+
+		// Based on https://dotenvx.com/docs/env-file
+		return {
+			'comment': /(?:(?<=^)|(?<=[\s"'`]))#(?![^\n"'`]*["'`])[^\r\n]*?(?=[ \t]*(?:\r?\n|$))/,
+			'keyword': /^export(?=\s)/m,
+			'key': {
+				// Allow bare keys (without values)
+				pattern: /[a-z_]\w*(?=\s*=|(?<!=.*)$)/im,
+				alias: 'constant',
+			},
+			'value': [
+				{
+					// Some implementations support empty values that are interpreted as empty strings
+					pattern: /(?<==)(?=\s*$)/,
+					alias: 'empty',
+				},
+				{
+					pattern: /(?<==\s*)(?:-?[1-9]\d*|0)(?:\.\d+)?(?=\s*$)/,
+					alias: 'number',
+				},
+				{
+					pattern: /(?<==\s*)(?:false|true)(?=\s*$)/,
+					alias: 'boolean',
+				},
+				{
+					pattern:
+						/(?<==\s*)(?:(['"`])((?:\\.|(?!\1)[\s\S])*?)\1|(?:\S.*?\S))(?=(?:\s+#.*)?\s*$)/m,
+					alias: 'string',
+					inside: {
+						'command-substitution': {
+							// Command substitution is disabled in strings enclosed in "'" (single quotes) and "`" (backticks)
+							pattern: /(?<!['`][\s\S]*)\$\(.+\)/,
+							inside: {
+								'command-substitution-punctuation': {
+									pattern: /\$\(|\)/,
+									alias: 'punctuation',
+								},
+								'shell-command': {
+									pattern: /.+/,
+									inside: 'bash',
+								},
+							},
+						},
+						'variable-expansion': {
+							// Variable expansion is disabled in strings enclosed in "'" (single quotes) and "`" (backticks)
+							pattern: /(?<!['`][\s\S]*)\$(\{[^{]+\}|[^\s"]+)/,
+							inside: {
+								'variable': /(?<=\$\{|\$(?!\{))[a-z_]\w*/i,
+								'default-value': commonPatterns(/(?<=(?::-|-)\s*)/),
+								'alternative-value': commonPatterns(/(?<=(?::\+|\+)\s*)/),
+								'variable-expansion-punctuation': {
+									pattern: /\$\{|:-|:\+|[$}+-]/,
+									alias: 'punctuation',
+								},
+							},
+						},
+						'escape-sequence': {
+							pattern: /\\['"`#\\nrt]/,
+							alias: 'char',
+						},
+						'punctuation': /^['"`]|['"`]$/,
+					},
+				},
+			],
+			'assignment-operator': {
+				pattern: /=/,
+				alias: 'operator',
+			},
+		};
+	},
+};
+
+/** @import { GrammarToken, LanguageProto } from '../types.d.ts'; */

From 3929c664b28cac4d69faf7181abfd7fe85cd80f4 Mon Sep 17 00:00:00 2001
From: Dmitry Sharabin <dmitrysharabin@gmail.com>
Date: Fri, 19 Dec 2025 09:31:31 +0100
Subject: [PATCH 02/11] Register the Dotenv language

---
 src/components.json | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/components.json b/src/components.json
index 7dfe6d098d..5cacba8d26 100644
--- a/src/components.json
+++ b/src/components.json
@@ -387,6 +387,10 @@
 			"title": "DOT (Graphviz)",
 			"owner": "RunDevelopment"
 		},
+		"dotenv": {
+			"title": "Dotenv",
+			"owner": "dmitrysharabin"
+		},
 		"ebnf": {
 			"title": "EBNF",
 			"owner": "RunDevelopment"

From 93da66174f7bb9500a130c620da756a8ab34fc2d Mon Sep 17 00:00:00 2001
From: Dmitry Sharabin <dmitrysharabin@gmail.com>
Date: Fri, 19 Dec 2025 09:29:50 +0100
Subject: [PATCH 03/11] Add tests

---
 .../languages/dotenv+bash/bash_inclusion.test |  44 +++
 .../dotenv/command_substitution_feature.test  | 115 ++++++
 tests/languages/dotenv/comment_feature.test   |  90 +++++
 .../dotenv/export_keyword_feature.test        |  14 +
 .../dotenv/key_value_pair_feature.test        | 122 +++++++
 .../dotenv/variable_expansion_feature.test    | 343 ++++++++++++++++++
 6 files changed, 728 insertions(+)
 create mode 100644 tests/languages/dotenv+bash/bash_inclusion.test
 create mode 100644 tests/languages/dotenv/command_substitution_feature.test
 create mode 100644 tests/languages/dotenv/comment_feature.test
 create mode 100644 tests/languages/dotenv/export_keyword_feature.test
 create mode 100644 tests/languages/dotenv/key_value_pair_feature.test
 create mode 100644 tests/languages/dotenv/variable_expansion_feature.test

diff --git a/tests/languages/dotenv+bash/bash_inclusion.test b/tests/languages/dotenv+bash/bash_inclusion.test
new file mode 100644
index 0000000000..e84e7b3a51
--- /dev/null
+++ b/tests/languages/dotenv+bash/bash_inclusion.test
@@ -0,0 +1,44 @@
+SHORT_HASH=$(git rev-parse --short HEAD)
+PWD_MESSAGE="Running from $(pwd)"
+DATABASE_URL=postgres://$(whoami)@localhost/my_database
+
+----------------------------------------------------
+
+[
+	["assign-left", ["SHORT_HASH"]],
+	["operator", ["="]],
+	["variable", [
+		["variable", "$("],
+		["function", "git"],
+		" rev-parse ",
+		["parameter", "--short"],
+		" HEAD",
+		["variable", ")"]
+	]],
+
+	["assign-left", ["PWD_MESSAGE"]],
+	["operator", ["="]],
+	["string", [
+		"\"Running from ",
+		["variable", [
+			["variable", "$("],
+			["builtin", "pwd"],
+			["variable", ")"]
+		]],
+		"\""
+	]],
+
+	["assign-left", ["DATABASE_URL"]],
+	["operator", ["="]],
+	"postgres://",
+	["variable", [
+		["variable", "$("],
+		["function", "whoami"],
+		["variable", ")"]
+	]],
+	"@localhost/my_database"
+]
+
+----------------------------------------------------
+
+Check for bash inclusion.
diff --git a/tests/languages/dotenv/command_substitution_feature.test b/tests/languages/dotenv/command_substitution_feature.test
new file mode 100644
index 0000000000..e28a91ab7d
--- /dev/null
+++ b/tests/languages/dotenv/command_substitution_feature.test
@@ -0,0 +1,115 @@
+DATE=$(date)
+SHORT_HASH=$(git rev-parse --short HEAD)
+LONG_HASH=`git rev-parse HEAD`
+BUILD_ID="build-$(uuidgen)"
+PWD_MESSAGE="Running from $(pwd)"
+
+DATABASE_URL="postgres://$(whoami)@localhost/my_database"
+WITH_SUBSTITUTION=postgres://$(whoami)@localhost/my_database
+NO_SUBSTITUTION='postgres://$(whoami)@localhost/my_database'
+AND_HERE=`Some text...
+postgres://$(whoami)@localhost/my_database`
+
+----------------------------------------------------
+
+[
+	["key", "DATE"],
+	["assignment-operator", "="],
+	["value", [
+		["command-substitution", [
+			["command-substitution-punctuation", "$("],
+			["shell-command", "date"],
+			["command-substitution-punctuation", ")"]
+		]]
+	]],
+
+	["key", "SHORT_HASH"],
+	["assignment-operator", "="],
+	["value", [
+		["command-substitution", [
+			["command-substitution-punctuation", "$("],
+			["shell-command", "git rev-parse --short HEAD"],
+			["command-substitution-punctuation", ")"]
+		]]
+	]],
+
+	["key", "LONG_HASH"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "`"],
+		"git rev-parse HEAD",
+		["punctuation", "`"]
+	]],
+
+	["key", "BUILD_ID"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "\""],
+		"build-",
+		["command-substitution", [
+			["command-substitution-punctuation", "$("],
+			["shell-command", "uuidgen"],
+			["command-substitution-punctuation", ")"]
+		]],
+		["punctuation", "\""]
+	]],
+
+	["key", "PWD_MESSAGE"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "\""],
+		"Running from ",
+		["command-substitution", [
+			["command-substitution-punctuation", "$("],
+			["shell-command", "pwd"],
+			["command-substitution-punctuation", ")"]
+		]],
+		["punctuation", "\""]
+	]],
+
+	["key", "DATABASE_URL"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "\""],
+		"postgres://",
+		["command-substitution", [
+			["command-substitution-punctuation", "$("],
+			["shell-command", "whoami"],
+			["command-substitution-punctuation", ")"]
+		]],
+		"@localhost/my_database",
+		["punctuation", "\""]
+	]],
+
+	["key", "WITH_SUBSTITUTION"],
+	["assignment-operator", "="],
+	["value", [
+		"postgres://",
+		["command-substitution", [
+			["command-substitution-punctuation", "$("],
+			["shell-command", "whoami"],
+			["command-substitution-punctuation", ")"]
+		]],
+		"@localhost/my_database"
+	]],
+
+	["key", "NO_SUBSTITUTION"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "'"],
+		"postgres://$(whoami)@localhost/my_database",
+		["punctuation", "'"]
+	]],
+
+	["key", "AND_HERE"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "`"],
+		"Some text...\r\npostgres://$(whoami)@localhost/my_database",
+		["punctuation", "`"]
+	]]
+]
+
+----------------------------------------------------
+
+Check for command substitution.
diff --git a/tests/languages/dotenv/comment_feature.test b/tests/languages/dotenv/comment_feature.test
new file mode 100644
index 0000000000..5a39d6f675
--- /dev/null
+++ b/tests/languages/dotenv/comment_feature.test
@@ -0,0 +1,90 @@
+# This is a comment
+
+KEY=VAL # inline comment
+KEY="VAL"# and another one
+KEY='VAL'# and another one
+KEY=`VAL`# and another one
+
+KEY="String with a hash # this is not a comment"
+KEY='String with a hash # this is not a comment'
+KEY=`String with a hash # this is not a comment`
+KEY=VAL# also not a comment
+KEY=Escaped \# hash is not a comment as well
+
+----------------------------------------------------
+
+[
+	["comment", "# This is a comment"],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", ["VAL"]],
+	["comment", "# inline comment"],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "\""],
+		"VAL",
+		["punctuation", "\""]
+	]],
+	["comment", "# and another one"],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "'"],
+		"VAL",
+		["punctuation", "'"]
+	]],
+	["comment", "# and another one"],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "`"],
+		"VAL",
+		["punctuation", "`"]
+	]],
+	["comment", "# and another one"],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "\""],
+		"String with a hash # this is not a comment",
+		["punctuation", "\""]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "'"],
+		"String with a hash # this is not a comment",
+		["punctuation", "'"]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "`"],
+		"String with a hash # this is not a comment",
+		["punctuation", "`"]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", ["VAL# also not a comment"]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		"Escaped ",
+		["escape-sequence", "\\#"],
+		" hash is not a comment as well"
+	]]
+]
+
+----------------------------------------------------
+
+Check for comments.
diff --git a/tests/languages/dotenv/export_keyword_feature.test b/tests/languages/dotenv/export_keyword_feature.test
new file mode 100644
index 0000000000..255a038f39
--- /dev/null
+++ b/tests/languages/dotenv/export_keyword_feature.test
@@ -0,0 +1,14 @@
+export EXPORTED_VAR=value
+
+----------------------------------------------------
+
+[
+	["keyword", "export"],
+	["key", "EXPORTED_VAR"],
+	["assignment-operator", "="],
+	["value", ["value"]]
+]
+
+----------------------------------------------------
+
+Check for the export keyword.
diff --git a/tests/languages/dotenv/key_value_pair_feature.test b/tests/languages/dotenv/key_value_pair_feature.test
new file mode 100644
index 0000000000..2ffe210f44
--- /dev/null
+++ b/tests/languages/dotenv/key_value_pair_feature.test
@@ -0,0 +1,122 @@
+APP_ENV=production
+API_VERSION=1.2.3
+LOG=true
+USERS_COUNT=42
+TIMEOUT=30.5
+
+BARE_KEY
+EMPTY_STRING=
+#DISABLED_VAR=value
+
+APP_NAME="My App"
+WELCOME="Hello\nWorld"
+PASSWORD='literal#string'
+ESCAPED="He said: \"Hello\""
+
+HOST=example.com
+PORT=8080
+ENABLE=true
+SPECIAL=some\#literal
+
+MULTILINE=`line 1 \
+line 2 \
+line 3`
+
+SPACEY   =   spaced-value
+TABS		=	value-with-tabs
+TABS_AND_SPACES   		=   	value-with-tabs-and-spaces
+
+----------------------------------------------------
+
+[
+	["key", "APP_ENV"], ["assignment-operator", "="], ["value", ["production"]],
+	["key", "API_VERSION"], ["assignment-operator", "="], ["value", ["1.2.3"]],
+	["key", "LOG"], ["assignment-operator", "="], ["value", "true"],
+	["key", "USERS_COUNT"], ["assignment-operator", "="], ["value", "42"],
+	["key", "TIMEOUT"], ["assignment-operator", "="], ["value", "30.5"],
+
+	["key", "BARE_KEY"],
+	["key", "EMPTY_STRING"], ["assignment-operator", "="], ["value", ""],
+	["comment", "#DISABLED_VAR=value"],
+
+	["key", "APP_NAME"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "\""],
+		"My App",
+		["punctuation", "\""]
+	]],
+
+	["key", "WELCOME"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "\""],
+		"Hello",
+		["escape-sequence", "\\n"],
+		"World",
+		["punctuation", "\""]
+	]],
+
+	["key", "PASSWORD"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "'"],
+		"literal#string",
+		["punctuation", "'"]
+	]],
+
+	["key", "ESCAPED"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "\""],
+		"He said: ",
+		["escape-sequence", "\\\""],
+		"Hello",
+		["escape-sequence", "\\\""],
+		["punctuation", "\""]
+	]],
+
+	["key", "HOST"],
+	["assignment-operator", "="],
+	["value", ["example.com"]],
+
+	["key", "PORT"],
+	["assignment-operator", "="],
+	["value", "8080"],
+
+	["key", "ENABLE"],
+	["assignment-operator", "="],
+	["value", "true"],
+
+	["key", "SPECIAL"],
+	["assignment-operator", "="],
+	["value", [
+		"some",
+		["escape-sequence", "\\#"],
+		"literal"
+	]],
+
+	["key", "MULTILINE"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "`"],
+		"line 1 \\\r\nline 2 \\\r\nline 3",
+		["punctuation", "`"]
+	]],
+
+	["key", "SPACEY"],
+	["assignment-operator", "="],
+	["value", ["spaced-value"]],
+
+	["key", "TABS"],
+	["assignment-operator", "="],
+	["value", ["value-with-tabs"]],
+
+	["key", "TABS_AND_SPACES"],
+	["assignment-operator", "="],
+	["value", ["value-with-tabs-and-spaces"]]
+]
+
+----------------------------------------------------
+
+Check for key-value pairs.
diff --git a/tests/languages/dotenv/variable_expansion_feature.test b/tests/languages/dotenv/variable_expansion_feature.test
new file mode 100644
index 0000000000..8c486c3328
--- /dev/null
+++ b/tests/languages/dotenv/variable_expansion_feature.test
@@ -0,0 +1,343 @@
+HELLO="Hi, ${NAME}"
+FULL="${HELLO}, welcome to ${APP_ENV}"
+
+INTERPOLATED=Multiple $FOO:+false ${BAR-main}\nLines of text
+ALSO_INTERPOLATED="Multiple\nLines with a var ${BAZ+42} and an escape sequence \" "
+NON_INTERPOLATED='Text without variable (like, $YOLO) interpolation'
+MULTILINE_NON_INTERPOLATED=`Long text here (with escape sequences, like \`
+or similar),
+e.g. a private SSH key (without $VAR interpolation)`
+
+KEY=${FOO:-default}
+KEY=${FOO:-false}
+KEY=${FOO:-true value}
+KEY=$FOO:-false
+KEY=$FOO:-false value
+KEY=${FOO--42}
+KEY=$FOO-42 years
+KEY=${FOO:--15}
+
+KEY=${BAR:+alternative}
+KEY=${BAR+true}
+KEY=${BAR+false value}
+KEY=$BAR+true
+KEY=$BAR+true value
+KEY=${BAR:+42}
+KEY=${BAR:+-42}
+KEY=${BAR:+42 years}
+KEY=$BAR:+42 years
+KEY="$FOO:+42"
+
+----------------------------------------------------
+
+[
+	["key", "HELLO"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "\""],
+		"Hi, ",
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "NAME"],
+			["variable-expansion-punctuation", "}"]
+		]],
+		["punctuation", "\""]
+	]],
+
+	["key", "FULL"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "\""],
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "HELLO"],
+			["variable-expansion-punctuation", "}"]
+		]],
+		", welcome to ",
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "APP_ENV"],
+			["variable-expansion-punctuation", "}"]
+		]],
+		["punctuation", "\""]
+	]],
+
+	["key", "INTERPOLATED"],
+	["assignment-operator", "="],
+	["value", [
+		"Multiple ",
+		["variable-expansion", [
+			["variable-expansion-punctuation", "$"],
+			["variable", "FOO"],
+			["variable-expansion-punctuation", ":+"],
+			["alternative-value", "false"]
+		]],
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "BAR"],
+			["variable-expansion-punctuation", "-"],
+			["default-value", "main"],
+			["variable-expansion-punctuation", "}"]
+		]],
+		["escape-sequence", "\\n"],
+		"Lines of text"
+	]],
+
+	["key", "ALSO_INTERPOLATED"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "\""],
+		"Multiple",
+		["escape-sequence", "\\n"],
+		"Lines with a var ",
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "BAZ"],
+			["variable-expansion-punctuation", "+"],
+			["alternative-value", "42"],
+			["variable-expansion-punctuation", "}"]
+		]],
+		" and an escape sequence ",
+		["escape-sequence", "\\\""],
+		["punctuation", "\""]
+	]],
+
+	["key", "NON_INTERPOLATED"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "'"],
+		"Text without variable (like, $YOLO) interpolation",
+		["punctuation", "'"]
+	]],
+
+	["key", "MULTILINE_NON_INTERPOLATED"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "`"],
+		"Long text here (with escape sequences, like ",
+		["escape-sequence", "\\`"],
+
+		"\r\nor similar),\r\ne.g. a private SSH key (without $VAR interpolation)",
+		["punctuation", "`"]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "FOO"],
+			["variable-expansion-punctuation", ":-"],
+			["default-value", "default"],
+			["variable-expansion-punctuation", "}"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "FOO"],
+			["variable-expansion-punctuation", ":-"],
+			["default-value", "false"],
+			["variable-expansion-punctuation", "}"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "FOO"],
+			["variable-expansion-punctuation", ":-"],
+			["default-value", "true value"],
+			["variable-expansion-punctuation", "}"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "$"],
+			["variable", "FOO"],
+			["variable-expansion-punctuation", ":-"],
+			["default-value", "false"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "$"],
+			["variable", "FOO"],
+			["variable-expansion-punctuation", ":-"],
+			["default-value", "false"]
+		]],
+		" value"
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "FOO"],
+			["variable-expansion-punctuation", "-"],
+			["default-value", "-42"],
+			["variable-expansion-punctuation", "}"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "$"],
+			["variable", "FOO"],
+			["variable-expansion-punctuation", "-"],
+			["default-value", "42"]
+		]],
+		" years"
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "FOO"],
+			["variable-expansion-punctuation", ":-"],
+			["default-value", "-15"],
+			["variable-expansion-punctuation", "}"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "BAR"],
+			["variable-expansion-punctuation", ":+"],
+			["alternative-value", "alternative"],
+			["variable-expansion-punctuation", "}"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "BAR"],
+			["variable-expansion-punctuation", "+"],
+			["alternative-value", "true"],
+			["variable-expansion-punctuation", "}"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "BAR"],
+			["variable-expansion-punctuation", "+"],
+			["alternative-value", "false value"],
+			["variable-expansion-punctuation", "}"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "$"],
+			["variable", "BAR"],
+			["variable-expansion-punctuation", "+"],
+			["alternative-value", "true"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "$"],
+			["variable", "BAR"],
+			["variable-expansion-punctuation", "+"],
+			["alternative-value", "true"]
+		]],
+		" value"
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "BAR"],
+			["variable-expansion-punctuation", ":+"],
+			["alternative-value", "42"],
+			["variable-expansion-punctuation", "}"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "BAR"],
+			["variable-expansion-punctuation", ":+"],
+			["variable-expansion-punctuation", "-"],
+			["default-value", "42"],
+			["variable-expansion-punctuation", "}"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "${"],
+			["variable", "BAR"],
+			["variable-expansion-punctuation", ":+"],
+			["alternative-value", "42 years"],
+			["variable-expansion-punctuation", "}"]
+		]]
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["variable-expansion", [
+			["variable-expansion-punctuation", "$"],
+			["variable", "BAR"],
+			["variable-expansion-punctuation", ":+"],
+			["alternative-value", "42"]
+		]],
+		" years"
+	]],
+
+	["key", "KEY"],
+	["assignment-operator", "="],
+	["value", [
+		["punctuation", "\""],
+		["variable-expansion", [
+			["variable-expansion-punctuation", "$"],
+			["variable", "FOO"],
+			["variable-expansion-punctuation", ":+"],
+			["alternative-value", "42"]
+		]],
+		["punctuation", "\""]
+	]]
+]
+
+----------------------------------------------------
+
+Check for interpolation (also known as variable expansion).

From 9bfb6bc9f9645f6b589c0cb4646e56e20a33e207 Mon Sep 17 00:00:00 2001
From: Dmitry Sharabin <dmitrysharabin@gmail.com>
Date: Thu, 18 Dec 2025 16:40:27 +0100
Subject: [PATCH 04/11] Simplify regexes

---
 src/languages/dotenv.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/languages/dotenv.js b/src/languages/dotenv.js
index 7d0c90ae8b..13bce0305b 100644
--- a/src/languages/dotenv.js
+++ b/src/languages/dotenv.js
@@ -30,7 +30,7 @@ export default {
 
 		// Based on https://dotenvx.com/docs/env-file
 		return {
-			'comment': /(?:(?<=^)|(?<=[\s"'`]))#(?![^\n"'`]*["'`])[^\r\n]*?(?=[ \t]*(?:\r?\n|$))/,
+			'comment': /(?:^|(?<=[\s"'`]))#(?![^\n"'`]*["'`])[^\r\n]*?(?=[ \t]*(?:\r?\n|$))/,
 			'keyword': /^export(?=\s)/m,
 			'key': {
 				// Allow bare keys (without values)
@@ -53,7 +53,7 @@ export default {
 				},
 				{
 					pattern:
-						/(?<==\s*)(?:(['"`])((?:\\.|(?!\1)[\s\S])*?)\1|(?:\S.*?\S))(?=(?:\s+#.*)?\s*$)/m,
+						/(?<==\s*)(?:(['"`])((?:\\.|(?!\1)[\s\S])*?)\1|\S.*?\S)(?=(?:\s+#.*)?\s*$)/m,
 					alias: 'string',
 					inside: {
 						'command-substitution': {
@@ -74,7 +74,7 @@ export default {
 							// Variable expansion is disabled in strings enclosed in "'" (single quotes) and "`" (backticks)
 							pattern: /(?<!['`][\s\S]*)\$(\{[^{]+\}|[^\s"]+)/,
 							inside: {
-								'variable': /(?<=\$\{|\$(?!\{))[a-z_]\w*/i,
+								'variable': /(?<=\$\{|\$)[a-z_]\w*/i,
 								'default-value': commonPatterns(/(?<=(?::-|-)\s*)/),
 								'alternative-value': commonPatterns(/(?<=(?::\+|\+)\s*)/),
 								'variable-expansion-punctuation': {

From 558eb4d8b2791f27f536169f92790b151c2c2a93 Mon Sep 17 00:00:00 2001
From: Dmitry Sharabin <dmitrysharabin@gmail.com>
Date: Thu, 18 Dec 2025 17:10:47 +0100
Subject: [PATCH 05/11] Fix possible backtracking in the `comment` pattern

---
 src/languages/dotenv.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/languages/dotenv.js b/src/languages/dotenv.js
index 13bce0305b..f9b5a125c5 100644
--- a/src/languages/dotenv.js
+++ b/src/languages/dotenv.js
@@ -30,7 +30,8 @@ export default {
 
 		// Based on https://dotenvx.com/docs/env-file
 		return {
-			'comment': /(?:^|(?<=[\s"'`]))#(?![^\n"'`]*["'`])[^\r\n]*?(?=[ \t]*(?:\r?\n|$))/,
+			'comment':
+				/(?:^|(?<=[\s"'`]))#(?![^\n"'`]*["'`])[^\r\n \t]*(?:[ \t]+[^\r\n \t]+)*[ \t]*/,
 			'keyword': /^export(?=\s)/m,
 			'key': {
 				// Allow bare keys (without values)

From 909128d645a3a4454d379079a686318f2fc287e3 Mon Sep 17 00:00:00 2001
From: Dmitry Sharabin <dmitrysharabin@gmail.com>
Date: Thu, 18 Dec 2025 17:26:49 +0100
Subject: [PATCH 06/11] Partially fix pattern tests

---
 src/languages/dotenv.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/languages/dotenv.js b/src/languages/dotenv.js
index f9b5a125c5..9c4f3d242e 100644
--- a/src/languages/dotenv.js
+++ b/src/languages/dotenv.js
@@ -22,7 +22,7 @@ export default {
 				},
 				{
 					// Ignore leading and trailing whitespace characters
-					pattern: RegExp(prefix.source + /(\S[^}]*?\S)(?=\s*\})/.source),
+					pattern: RegExp(prefix.source + /\S[^}]*?\S(?=\s*\})/.source),
 					alias: 'string',
 				},
 			];
@@ -54,7 +54,7 @@ export default {
 				},
 				{
 					pattern:
-						/(?<==\s*)(?:(['"`])((?:\\.|(?!\1)[\s\S])*?)\1|\S.*?\S)(?=(?:\s+#.*)?\s*$)/m,
+						/(?<==\s*)(?:(['"`])(?:\\.|(?!\1)[\s\S])*?\1|\S.*?\S)(?=(?:\s+#.*)?\s*$)/m,
 					alias: 'string',
 					inside: {
 						'command-substitution': {
@@ -73,7 +73,7 @@ export default {
 						},
 						'variable-expansion': {
 							// Variable expansion is disabled in strings enclosed in "'" (single quotes) and "`" (backticks)
-							pattern: /(?<!['`][\s\S]*)\$(\{[^{]+\}|[^\s"]+)/,
+							pattern: /(?<!['`][\s\S]*)\$(?:\{[^{]+\}|[^\s"]+)/,
 							inside: {
 								'variable': /(?<=\$\{|\$)[a-z_]\w*/i,
 								'default-value': commonPatterns(/(?<=(?::-|-)\s*)/),

From 3eb04a7e045661e0f702f118c53448f1b376f8cc Mon Sep 17 00:00:00 2001
From: Dmitry Sharabin <dmitrysharabin@gmail.com>
Date: Thu, 18 Dec 2025 18:05:45 +0100
Subject: [PATCH 07/11] Fix the `key` pattern

---
 src/languages/dotenv.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/languages/dotenv.js b/src/languages/dotenv.js
index 9c4f3d242e..ac447cfe6a 100644
--- a/src/languages/dotenv.js
+++ b/src/languages/dotenv.js
@@ -35,7 +35,7 @@ export default {
 			'keyword': /^export(?=\s)/m,
 			'key': {
 				// Allow bare keys (without values)
-				pattern: /[a-z_]\w*(?=\s*=|(?<!=.*)$)/im,
+				pattern: /(?<=^[ \t]*)[a-z_]\w*(?=[ \t]*(?:=|$))/im,
 				alias: 'constant',
 			},
 			'value': [

From 3ba47a78b55b070a082fdf8c94bf5b8d0976e905 Mon Sep 17 00:00:00 2001
From: Dmitry Sharabin <dmitrysharabin@gmail.com>
Date: Fri, 19 Dec 2025 08:46:54 +0100
Subject: [PATCH 08/11] Don't match the empty string

---
 src/languages/dotenv.js                            | 5 -----
 tests/languages/dotenv/key_value_pair_feature.test | 2 +-
 2 files changed, 1 insertion(+), 6 deletions(-)

diff --git a/src/languages/dotenv.js b/src/languages/dotenv.js
index ac447cfe6a..48bb42ba29 100644
--- a/src/languages/dotenv.js
+++ b/src/languages/dotenv.js
@@ -39,11 +39,6 @@ export default {
 				alias: 'constant',
 			},
 			'value': [
-				{
-					// Some implementations support empty values that are interpreted as empty strings
-					pattern: /(?<==)(?=\s*$)/,
-					alias: 'empty',
-				},
 				{
 					pattern: /(?<==\s*)(?:-?[1-9]\d*|0)(?:\.\d+)?(?=\s*$)/,
 					alias: 'number',
diff --git a/tests/languages/dotenv/key_value_pair_feature.test b/tests/languages/dotenv/key_value_pair_feature.test
index 2ffe210f44..de6b993f16 100644
--- a/tests/languages/dotenv/key_value_pair_feature.test
+++ b/tests/languages/dotenv/key_value_pair_feature.test
@@ -36,7 +36,7 @@ TABS_AND_SPACES   		=   	value-with-tabs-and-spaces
 	["key", "TIMEOUT"], ["assignment-operator", "="], ["value", "30.5"],
 
 	["key", "BARE_KEY"],
-	["key", "EMPTY_STRING"], ["assignment-operator", "="], ["value", ""],
+	["key", "EMPTY_STRING"], ["assignment-operator", "="],
 	["comment", "#DISABLED_VAR=value"],
 
 	["key", "APP_NAME"],

From ae060de24d82cfe80439652a2baad0f00189bae1 Mon Sep 17 00:00:00 2001
From: Dmitry Sharabin <dmitrysharabin@gmail.com>
Date: Fri, 19 Dec 2025 08:56:26 +0100
Subject: [PATCH 09/11] Fix polynomial backtracking

---
 src/languages/dotenv.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/languages/dotenv.js b/src/languages/dotenv.js
index 48bb42ba29..e5787e10b3 100644
--- a/src/languages/dotenv.js
+++ b/src/languages/dotenv.js
@@ -49,7 +49,7 @@ export default {
 				},
 				{
 					pattern:
-						/(?<==\s*)(?:(['"`])(?:\\.|(?!\1)[\s\S])*?\1|\S.*?\S)(?=(?:\s+#.*)?\s*$)/m,
+						/(?<==\s*)(?:(['"`])(?:\\.|(?!\1)[\s\S])*?\1|\S.*?\S)(?=\s*$|\s+#.*$)/m,
 					alias: 'string',
 					inside: {
 						'command-substitution': {

From d013aab137d6bedeb23f5760b51a7eac4ee799ae Mon Sep 17 00:00:00 2001
From: Dmitry Sharabin <dmitrysharabin@gmail.com>
Date: Fri, 19 Dec 2025 09:20:00 +0100
Subject: [PATCH 10/11] Fix exponential backtracking

---
 src/languages/dotenv.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/languages/dotenv.js b/src/languages/dotenv.js
index e5787e10b3..aa6ce87307 100644
--- a/src/languages/dotenv.js
+++ b/src/languages/dotenv.js
@@ -49,7 +49,7 @@ export default {
 				},
 				{
 					pattern:
-						/(?<==\s*)(?:(['"`])(?:\\.|(?!\1)[\s\S])*?\1|\S.*?\S)(?=\s*$|\s+#.*$)/m,
+						/(?<==\s*)(?:(['"`])(?:\\[\s\S]|(?!\1)[^\\])*?\1|\S(?:.*?\S)?)(?=\s*$|\s+#.*$)/m,
 					alias: 'string',
 					inside: {
 						'command-substitution': {

From e1397c46fee22d57b974adcd47cf789702d7b7f2 Mon Sep 17 00:00:00 2001
From: Dmitry Sharabin <dmitrysharabin@gmail.com>
Date: Fri, 19 Dec 2025 09:31:50 +0100
Subject: [PATCH 11/11] Fix components order + tweak the language title

---
 src/components.json | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/components.json b/src/components.json
index 5cacba8d26..6a6246c4be 100644
--- a/src/components.json
+++ b/src/components.json
@@ -383,14 +383,14 @@
 			"title": "Docker",
 			"owner": "JustinBeckwith"
 		},
+		"dotenv": {
+			"title": "Dotenv (.env)",
+			"owner": "DmitrySharabin"
+		},
 		"dot": {
 			"title": "DOT (Graphviz)",
 			"owner": "RunDevelopment"
 		},
-		"dotenv": {
-			"title": "Dotenv",
-			"owner": "dmitrysharabin"
-		},
 		"ebnf": {
 			"title": "EBNF",
 			"owner": "RunDevelopment"