parser: allow empty identifiers

CHANGELOG.md

@@ -1,3 +1,9 @@
+# Unreleased
+
+**Improvements**
+
+* Allow empty commands, keys, and prefixes.
+
 # 0.5.0 (2024-05-31)
 
 **Bug Fixes**

src/lib.rs

@@ -185,7 +185,7 @@
 //!
 //! ## Commands
 //!
-//! A [`Command`] must have a command name, which can be any arbitrary non-empty
+//! A [`Command`] must have a command name, which can be any arbitrary
 //! [string](#strings), e.g.:
 //!
 //! ```text
@@ -198,8 +198,9 @@
 //!
 //! * [**Arguments:**](Argument) any number of space-separated arguments.
 //!   These have a string [value](Argument::value), and optionally also a string
-//!   [key](Argument::key) as `key=value`. Values can be empty, and duplicate
-//!   keys are allowed by the parser (the runner can handle this as desired).
+//!   [key](Argument::key) as `key=value`. Keys and values can be empty, and
+//!   duplicate keys are allowed by the parser (the runner can handle this as
+//!   desired).
 //!
 //!     ```text
 //!     command argument key=value

src/parser.rs

@@ -99,13 +99,13 @@ fn command(input: Span) -> IResult<Command> {
     let silent = maybe_silent.is_some();
 
     // The prefix and fail marker.
-    let (input, prefix) = opt(terminated(identifier, pair(tag(":"), space0)))(input)?;
+    let (input, prefix) = opt(terminated(string, pair(tag(":"), space0)))(input)?;
     let (input, maybe_fail) = opt(terminated(char('!'), space0))(input)?;
     let fail = maybe_fail.is_some();
 
     // The command itself.
     let line_number = input.location_line();
-    let (input, name) = identifier(input)?;
+    let (input, name) = string(input)?;
     let (mut input, args) = many0(preceded(space1, argument))(input)?;
 
     // If silenced, look for the closing brace.
@@ -124,7 +124,7 @@ fn command(input: Span) -> IResult<Command> {
 /// Parses a single command argument, consisting of an argument value and
 /// optionally a key separated by =.
 fn argument(input: Span) -> IResult<Argument> {
-    if let Ok((input, (key, value))) = separated_pair(identifier, tag("="), opt(string))(input) {
+    if let Ok((input, (key, value))) = separated_pair(string, tag("="), opt(string))(input) {
         return Ok((input, Argument { key: Some(key), value: value.unwrap_or_default() }));
     }
     let (input, value) = string(input)?;
@@ -148,12 +148,6 @@ fn output(input: Span) -> IResult<Span> {
     recognize(many_till(anychar, pair(alt((line_ending, eof)), alt((line_ending, eof)))))(input)
 }
 
-/// Parses an identifier. This is any unquoted or quoted string that
-/// isn't entirely empty.
-fn identifier(input: Span) -> IResult<String> {
-    verify(string, |s: &str| !s.is_empty())(input)
-}
-
 /// Parses a string, both quoted (' or ") and unquoted.
 fn string(input: Span) -> IResult<String> {
     alt((unquoted_string, quoted_string('\''), quoted_string('"')))(input)

tests/scripts/commands

@@ -24,17 +24,21 @@ b: Command { name: "bar", args: [Argument { key: Some("key"), value: "value" }],
 ---
 Error: Command { name: "foo", args: [Argument { key: None, value: "bar" }], prefix: None, silent: false, fail: true, line_number: 23 }
 
-# Both prefixes, commands, and argument identifiers can be whitespace, but not
-# empty (tested under errors/).
+# Prefixes, commands, and keys can be empty.
+"": "" ""=""
+---
+: Command { name: "", args: [Argument { key: Some(""), value: "" }], prefix: Some(""), silent: false, fail: false, line_number: 28 }
+
+# Prefixes, commands, and keys can be whitespace.
 " ": " " " "=" "
 ---
- : Command { name: " ", args: [Argument { key: Some(" "), value: " " }], prefix: Some(" "), silent: false, fail: false, line_number: 29 }
+ : Command { name: " ", args: [Argument { key: Some(" "), value: " " }], prefix: Some(" "), silent: false, fail: false, line_number: 33 }
 
-# Empty argument values are fine.
+# Empty argument keys and values are fine.
 command ""
 command arg=""
 command arg=
 ---
-Command { name: "command", args: [Argument { key: None, value: "" }], prefix: None, silent: false, fail: false, line_number: 34 }
-Command { name: "command", args: [Argument { key: Some("arg"), value: "" }], prefix: None, silent: false, fail: false, line_number: 35 }
-Command { name: "command", args: [Argument { key: Some("arg"), value: "" }], prefix: None, silent: false, fail: false, line_number: 36 }
+Command { name: "command", args: [Argument { key: None, value: "" }], prefix: None, silent: false, fail: false, line_number: 38 }
+Command { name: "command", args: [Argument { key: Some("arg"), value: "" }], prefix: None, silent: false, fail: false, line_number: 39 }
+Command { name: "command", args: [Argument { key: Some("arg"), value: "" }], prefix: None, silent: false, fail: false, line_number: 40 }