First implementation of the actual parser.

It doesn't do proper error handling yet, and is completely untested
so it probably has tons of bugs in it.

src/lib.rs

@@ -1,189 +1,149 @@
-use std::collections::{HashMap, HashSet};
+use std::collections::HashMap;
 use std::env::args_os;
-use std::ffi::{OsStr, OsString};
+use std::ffi::OsString;
-use std::ops::RangeBounds;
 
-/// A command line argument parser.
+mod spec;
-#[derive(Debug, Clone)]
-pub struct Parser {
-    args: Vec<Arg>,
 
-    // Used to ensure we don't get duplicate arguments.
+pub use spec::Spec;
-    id_set: HashSet<String>,
-    long_set: HashSet<String>,
-    short_set: HashSet<String>,
-}
 
-impl Parser {
+pub fn parse(mut spec: Spec) -> ParsedArguments {
-    pub fn new() -> Parser {
+    // Split into non-positional and positional arguments.
-        Parser {
+    let (args, pos_args): (Vec<_>, Vec<_>) = spec
-            args: Vec::new(),
+        .args
-            id_set: HashSet::new(),
+        .drain(..)
-            long_set: HashSet::new(),
+        .partition(|arg| arg.arg_type != spec::ArgType::Pos);
-            short_set: HashSet::new(),
-        }
-    }
 
-    /// Add a flag (bool) argument.
+    // Validate positional arguments:
-    ///
+    // - All required positional arguments should precede any optional
-    /// - `id`: the argument identifier, used for fetching argument
+    //   positional arguments.
-    ///   matches.
+    // - There should be at most a single positional multi-argument, and
-    /// - `flags`: the long and/or short argument flag strings.  Must be
+    //   it must be at the end.
-    ///   in the form "-f" or "--flag".  You can pass as many as you
+    {
-    ///   like, all of which will be considered equivalent during
+        let mut met_optional = false;
-    ///   parsing.  But there must be at least one.
+        let mut met_multi = false;
-    /// - `doc`: the documentation string to use in the generated help.
+        for arg in pos_args.iter() {
-    ///   Pass an empty string to indicate no documentation.
+            if arg.arg_type == spec::ArgType::Pos {
-    pub fn add_flag(&mut self, id: &str, flags: &[&str], doc: &str) {
+                let is_optional = arg.acceptable_count.0 == 0;
-        let (long_flags, short_flags) = self.validate_and_process_arg(id, flags);
+                let is_multi =
+                    arg.acceptable_count.1.is_none() || arg.acceptable_count.1.unwrap() > 1;
 
-        self.args.push(Arg {
+                if !is_optional && met_optional {
-            arg_type: ArgType::Flag,
+                    panic!("All required positional arguments must precede all optional positional arguments in the argument spec.")
-            id: id.into(),
+                }
-            value_label: String::new(),
+                if met_multi {
-            long_flags: long_flags,
+                    panic!("There must be at most one positional multi-argument in the argument spec, and it must come last.")
-            short_flags: short_flags,
+                }
-            acceptable_count: (0, None),
-            doc: doc.into(),
-        });
-    }
 
-    /// Add a standard argument, that takes a value.
+                met_optional |= is_optional;
-    pub fn add_argument(
+                met_multi |= is_multi;
-        &mut self,
-        id: &str,
-        flags: &[&str],
-        doc: &str,
-        value_label: &str,
-        required: bool,
-    ) {
-        let (long_flags, short_flags) = self.validate_and_process_arg(id, flags);
-
-        self.args.push(Arg {
-            arg_type: ArgType::Arg,
-            id: id.into(),
-            value_label: value_label.into(),
-            long_flags: long_flags,
-            short_flags: short_flags,
-            acceptable_count: (if required { 1 } else { 0 }, None),
-            doc: doc.into(),
-        });
-    }
-
-    /// Add a positional argument.
-    ///
-    /// Unlike flags and standard arguments, positional arguments are
-    /// parsed in the order they're added.  Because of their nature,
-    /// they have some additional considerations:
-    ///
-    /// - All required positional arguments must precede all optional
-    ///   positional arguments.
-    /// - There can at most be a single positional multi-argument,
-    ///   which must come last.  (See `add_positional_multi_argument()`.)
-    pub fn add_positional_argument(
-        &mut self,
-        id: &str,
-        doc: &str,
-        value_label: &str,
-        required: bool,
-    ) {
-        let (_, _) = self.validate_and_process_arg(id, &[]);
-
-        self.args.push(Arg {
-            arg_type: ArgType::PosArg,
-            id: id.into(),
-            value_label: value_label.into(),
-            long_flags: Vec::new(),
-            short_flags: Vec::new(),
-            acceptable_count: (if required { 1 } else { 0 }, Some(1)),
-            doc: doc.into(),
-        });
-    }
-
-    pub fn add_positional_multi_argument(
-        &mut self,
-        id: &str,
-        doc: &str,
-        value_label: &str,
-        required: bool,
-    ) {
-        let (_, _) = self.validate_and_process_arg(id, &[]);
-
-        self.args.push(Arg {
-            arg_type: ArgType::PosArg,
-            id: id.into(),
-            value_label: value_label.into(),
-            long_flags: Vec::new(),
-            short_flags: Vec::new(),
-            acceptable_count: (if required { 1 } else { 0 }, None),
-            doc: doc.into(),
-        });
-    }
-
-    //----------------
-
-    pub fn parse(self) -> ParsedArguments {
-        todo!()
-    }
-
-    //----------------
-
-    /// Returns (long, short) pair, each of which is a Vec of argument strings with
-    /// the leading hyphens stripped off.
-    fn validate_and_process_arg(&mut self, id: &str, flags: &[&str]) -> (Vec<String>, Vec<String>) {
-        if self.id_set.contains(id) {
-            panic!(
-                "Error: attempted to add argument with a duplicate ID \"{}\".",
-                id
-            );
-        }
-        self.id_set.insert(id.into());
-
-        let mut long_flags = Vec::new();
-        let mut short_flags = Vec::new();
-
-        for &flag in flags {
-            // Ensure no whitespace.
-            if flag.len() != flag.trim().len() || flag.split_whitespace().count() > 1 {
-                panic!(
-                    "Error: attempted to add argument \"{}\" which contains whitespace.",
-                    flag
-                );
             }
-            // Long flags.
+        }
-            else if flag.starts_with("--") && flag.len() > 2 {
+    }
-                if self.long_set.contains(flag) {
+
-                    panic!(
+    // Parse!
-                        "Error: attempted to add duplicate long argument \"{}\".",
+    // TODO: optimize by first creating a hash map from flag strings to
-                        flag
+    // argument indices.  Right now this is an `O(NM)` algorithm, with N
+    // being the number of arguments in the spec and M being the number
+    // of arguments passed by the user.  We can even further optimize it
+    // by first checking against the maximum length of our long arguments,
+    // so we don't end up hashing really long user arguments
+    // unnecessarily for the check.
+    let mut pos_i = 0; // Index of the positional argument we're at.
+    let mut pos_i_count = 0; // Number of positional arguments we've parsed at the current positional argument index.
+    let mut parsed = ParsedArguments {
+        arguments: Vec::new(),
+        id_map: HashMap::new(),
+    };
+    let mut args_in = args_os();
+    let _ = args_in.next(); // Skip the first argument, which is the call to the executable.
+
+    'outer: while let Some(arg_in) = args_in.next() {
+        // Check for flags and non-positional arguments.
+        if let Some(arg_in_str) = arg_in.to_str() {
+            if arg_in_str.starts_with("--") {
+                // Long.
+                for arg in args.iter() {
+                    for long_flag in arg.long_flags.iter() {
+                        if arg_in_str == long_flag {
+                            match arg.arg_type {
+                                spec::ArgType::Flag => parsed.push_arg(arg.id.clone(), None),
+
+                                spec::ArgType::Arg => {
+                                    if let Some(value) = args_in.next() {
+                                        parsed.push_arg(arg.id.clone(), Some(value));
+                                    } else {
+                                        todo!("Handle error: expected value after argument flag.");
+                                    }
+                                }
+
+                                spec::ArgType::Pos => unreachable!(),
+                            }
+                            continue 'outer;
+                        }
+                    }
+                }
+                todo!("Handle error: no long argument matched the passed argument.");
+            } else if arg_in_str.starts_with("-") {
+                // Short.
+                let mut remainder = &arg_in_str[1..];
+
+                // First check arguments that take values.
+                for arg in args.iter().filter(|a| a.arg_type == spec::ArgType::Arg) {
+                    for short_flag in arg.short_flags.iter() {
+                        if remainder == short_flag {
+                            if let Some(value) = args_in.next() {
+                                parsed.push_arg(arg.id.clone(), Some(value));
+                            } else {
+                                todo!("Handle error: expected value after argument flag.");
+                            }
+                            continue 'outer;
+                        }
+                    }
+                }
+
+                // Then check boolean flags.  There can be multiple
+                // present, so we progressively chop off the front as we
+                // find matches until nothing remains.
+                'restart_args: while !remainder.is_empty() {
+                    for arg in args.iter().filter(|a| a.arg_type == spec::ArgType::Flag) {
+                        for short_flag in arg.short_flags.iter() {
+                            if remainder.starts_with(short_flag) {
+                                remainder = &remainder[short_flag.len()..];
+                                parsed.push_arg(arg.id.clone(), None);
+                                continue 'restart_args;
+                            }
+                        }
+                    }
+                    todo!(
+                        "Handle error: no short argument matches the next flag in \"{}\".",
+                        remainder
                     );
                 }
-                self.long_set.insert(flag.into());
+                continue 'outer;
-                long_flags.push((&flag[2..]).into());
-            }
-            // Check if it's a valid short flag (should only have one character
-            // after the hyphen).
-            else if flag.starts_with("-") && flag.chars().count() == 2 {
-                if self.short_set.contains(flag) {
-                    panic!(
-                        "Error: attempted to add duplicate short argument \"{}\".",
-                        flag
-                    );
-                }
-                self.short_set.insert(flag.into());
-                short_flags.push((&flag[1..]).into());
-            }
-            // Not a valid flag.
-            else {
-                panic!(
-                    "Error: attempted to add argument \"{}\", which isn't a valid argument string.",
-                    flag
-                )
             }
         }
 
-        (long_flags, short_flags)
+        if pos_i < pos_args.len() {
+            let arg = &pos_args[pos_i];
+            parsed.push_arg(arg.id.clone(), Some(arg_in));
+            pos_i_count += 1;
+
+            if let Some(max_count) = arg.acceptable_count.1 {
+                if pos_i_count == max_count {
+                    pos_i += 1;
+                    pos_i_count = 0;
+                }
+            }
+        } else {
+            todo!("Handle error: too many positional arguments.");
+        }
     }
+
+    if pos_i < pos_args.len() && pos_i_count < pos_args[pos_i].acceptable_count.0 {
+        todo!("Handle error: not enough positional arguments.");
+    }
+
+    parsed
 }
 
 /// Parsed command line arguments.
@@ -199,41 +159,15 @@ pub struct ParsedArguments {
     id_map: HashMap<String, Vec<usize>>, // Argument ID -> index list
 }
 
-//-------------------------------------------------------------
+impl ParsedArguments {
+    fn push_arg(&mut self, id: String, value: Option<OsString>) {
+        assert!(!id.is_empty());
 
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+        if !self.id_map.contains_key(&id) {
-enum ArgType {
+            self.id_map.insert(id.clone(), Vec::new());
-    Flag,
+        }
-    Arg,
+        self.id_map.get_mut(&id).unwrap().push(self.arguments.len());
-    PosArg,
+
-}
+        self.arguments.push((id, value));
-
+    }
-/// Argument specification.
-#[derive(Debug, Clone)]
-struct Arg {
-    arg_type: ArgType,
-    id: String,
-    value_label: String,
-
-    // Long and short versions of the argument flag.  E.g. "--curve" and
-    // "-c", but without the leading dashes.
-    long_flags: Vec<String>,
-    short_flags: Vec<String>,
-
-    // How many instances of the argument can be present, specified
-    // as a range.
-    //
-    // For example:
-    // - (0, None): An argument that can show up any number of times,
-    //              including not at all.
-    // - (0, 1):    An argument that can either be absent or show up
-    //              precisely once.
-    // - (1, 1):    An argument that must show up precisely once.
-    // - (1, None): An argument that must show up at least once.
-    // - (2, 9):    An argument that must show up at least twice, but
-    //              no more than 9 times.
-    acceptable_count: (usize, Option<usize>),
-
-    // Documentation string, for generated help.
-    doc: String,
 }

src/spec.rs

@@ -0,0 +1,244 @@
+use std::collections::HashSet;
+
+/// Command line argument specification.
+#[derive(Debug, Clone)]
+pub struct Spec {
+    pub(crate) name: String,    // Application name.
+    pub(crate) version: String, // Application version.
+    pub(crate) args: Vec<Arg>,
+
+    // Used to ensure we don't get duplicate arguments.
+    id_set: HashSet<String>,
+    long_set: HashSet<String>,
+    short_set: HashSet<String>,
+}
+
+impl Spec {
+    /// Create a new argument specification.
+    ///
+    /// `name` and `version` are the name and version of the software,
+    /// respectively.
+    #[must_use]
+    pub fn new(name: String, version: String) -> Spec {
+        Spec {
+            name: name,
+            version: version,
+
+            args: Vec::new(),
+
+            id_set: HashSet::new(),
+            long_set: HashSet::new(),
+            short_set: HashSet::new(),
+        }
+    }
+
+    /// Add a flag (bool) argument.
+    ///
+    /// - `id`: the argument identifier, used for fetching argument
+    ///   matches.
+    /// - `flags`: the long and/or short argument flag strings.  Must be
+    ///   in the form "-f" or "--flag".  You can pass as many as you
+    ///   like, all of which will be considered equivalent during
+    ///   parsing.  But there must be at least one.
+    /// - `doc`: the documentation string to use in the generated help.
+    ///   Pass an empty string to indicate no documentation.
+    #[must_use]
+    pub fn add_flag(mut self, id: &str, flags: &[&str], doc: &str) -> Self {
+        let (long_flags, short_flags) = self.validate_and_process_arg(id, flags);
+
+        self.args.push(Arg {
+            arg_type: ArgType::Flag,
+            id: id.into(),
+            value_label: String::new(),
+            long_flags: long_flags,
+            short_flags: short_flags,
+            acceptable_count: (0, None),
+            doc: doc.into(),
+        });
+
+        self
+    }
+
+    /// Add a standard argument, that takes a value.
+    #[must_use]
+    pub fn add_argument(
+        mut self,
+        id: &str,
+        flags: &[&str],
+        doc: &str,
+        value_label: &str,
+        required: bool,
+    ) -> Self {
+        let (long_flags, short_flags) = self.validate_and_process_arg(id, flags);
+
+        self.args.push(Arg {
+            arg_type: ArgType::Arg,
+            id: id.into(),
+            value_label: value_label.into(),
+            long_flags: long_flags,
+            short_flags: short_flags,
+            acceptable_count: (if required { 1 } else { 0 }, None),
+            doc: doc.into(),
+        });
+
+        self
+    }
+
+    /// Add a positional argument.
+    ///
+    /// Unlike flags and standard arguments, positional arguments are
+    /// parsed in the order they're added.  Because of their nature,
+    /// they have some additional considerations:
+    ///
+    /// - All required positional arguments must precede all optional
+    ///   positional arguments.
+    /// - There can at most be a single positional multi-argument,
+    ///   which must come last.  (See `add_positional_multi_argument()`.)
+    #[must_use]
+    pub fn add_positional_argument(
+        mut self,
+        id: &str,
+        doc: &str,
+        value_label: &str,
+        required: bool,
+    ) -> Self {
+        let (_, _) = self.validate_and_process_arg(id, &[]);
+
+        self.args.push(Arg {
+            arg_type: ArgType::Pos,
+            id: id.into(),
+            value_label: value_label.into(),
+            long_flags: Vec::new(),
+            short_flags: Vec::new(),
+            acceptable_count: (if required { 1 } else { 0 }, Some(1)),
+            doc: doc.into(),
+        });
+
+        self
+    }
+
+    #[must_use]
+    pub fn add_positional_multi_argument(
+        mut self,
+        id: &str,
+        doc: &str,
+        value_label: &str,
+        required: bool,
+    ) -> Self {
+        let (_, _) = self.validate_and_process_arg(id, &[]);
+
+        self.args.push(Arg {
+            arg_type: ArgType::Pos,
+            id: id.into(),
+            value_label: value_label.into(),
+            long_flags: Vec::new(),
+            short_flags: Vec::new(),
+            acceptable_count: (if required { 1 } else { 0 }, None),
+            doc: doc.into(),
+        });
+
+        self
+    }
+
+    //----------------
+
+    /// Returns (long, short) pair, each of which is a Vec of argument strings with
+    /// the leading hyphens stripped off.
+    fn validate_and_process_arg(&mut self, id: &str, flags: &[&str]) -> (Vec<String>, Vec<String>) {
+        if self.id_set.contains(id) {
+            panic!(
+                "Error: attempted to add argument with a duplicate ID \"{}\".",
+                id
+            );
+        }
+        self.id_set.insert(id.into());
+
+        let mut long_flags = Vec::new();
+        let mut short_flags = Vec::new();
+
+        for &flag in flags {
+            // Ensure no whitespace.
+            if flag.len() != flag.trim().len() || flag.split_whitespace().count() > 1 {
+                panic!(
+                    "Error: attempted to add argument \"{}\" which contains whitespace.",
+                    flag
+                );
+            }
+            // Long flags.
+            else if flag.starts_with("--") && flag.len() > 2 {
+                if self.long_set.contains(flag) {
+                    panic!(
+                        "Error: attempted to add duplicate long argument \"{}\".",
+                        flag
+                    );
+                }
+                self.long_set.insert(flag.into());
+                long_flags.push(flag.into());
+            }
+            // Check if it's a valid short flag.
+            // Note: in theory we should be checking to verify that
+            // the flag is only one character long.  But because of
+            // graphemes that's complicated, and it's not really
+            // worth all the code.  So instead we just rely on client
+            // code doing the right thing.
+            else if flag.starts_with("-") && flag.len() > 1 {
+                if self.short_set.contains(flag) {
+                    panic!(
+                        "Error: attempted to add duplicate short argument \"{}\".",
+                        flag
+                    );
+                }
+                self.short_set.insert(flag.into());
+                short_flags.push((&flag[1..]).into());
+            }
+            // Not a valid flag.
+            else {
+                panic!(
+                    "Error: attempted to add argument \"{}\", which isn't a valid argument string.",
+                    flag
+                )
+            }
+        }
+
+        (long_flags, short_flags)
+    }
+}
+
+//-------------------------------------------------------------
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub(crate) enum ArgType {
+    Flag, // Boolean flag (present or absent)
+    Arg,  // Standard flag+value argument, like `-i input_file`.
+    Pos,  // Positional argument.
+}
+
+/// Argument specification.
+#[derive(Debug, Clone)]
+pub(crate) struct Arg {
+    pub(crate) arg_type: ArgType,
+    pub(crate) id: String,
+    pub(crate) value_label: String,
+
+    // Long and short versions of the argument flag.  E.g. "--curve" and
+    // "-c", but without the leading dashes.
+    pub(crate) long_flags: Vec<String>,
+    pub(crate) short_flags: Vec<String>,
+
+    // How many instances of the argument can be present, specified
+    // as a range.
+    //
+    // For example:
+    // - (0, None): An argument that can show up any number of times,
+    //              including not at all.
+    // - (0, 1):    An argument that can either be absent or show up
+    //              precisely once.
+    // - (1, 1):    An argument that must show up precisely once.
+    // - (1, None): An argument that must show up at least once.
+    // - (2, 9):    An argument that must show up at least twice, but
+    //              no more than 9 times.
+    pub(crate) acceptable_count: (usize, Option<usize>),
+
+    // Documentation string, for generated help.
+    pub(crate) doc: String,
+}