feat: Add prqlc lex command to the CLI

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Initial implementation of an experimental documentation generator that
   generates Markdown documentation from `.prql` files. (@vanillajonathan,
   #4152).
+- Add `prqlc lex` command to the CLI (@max-sixty)
 
 **Fixes**:
 

prqlc/prqlc-parser/src/lib.rs

@@ -10,13 +10,12 @@ mod types;
 use chumsky::error::SimpleReason;
 use chumsky::{prelude::*, Stream};
 
-use prqlc_ast::error::Reason;
-use prqlc_ast::error::{Error, WithErrorInfo};
+use prqlc_ast::error::{Error, Reason, WithErrorInfo};
 use prqlc_ast::stmt::*;
 use prqlc_ast::Span;
 
-use lexer::TokenKind;
-use lexer::{Token, TokenVec};
+use lexer::Token;
+pub use lexer::{TokenKind, TokenVec};
 use span::ParserSpan;
 
 /// Build PRQL AST from a PRQL query string.

prqlc/prqlc/src/cli/mod.rs

@@ -22,10 +22,10 @@ use std::path::Path;
 use std::process::exit;
 use std::str::FromStr;
 
-use prqlc::ast;
 use prqlc::semantic;
 use prqlc::semantic::reporting::{collect_frames, label_references};
 use prqlc::semantic::NS_DEFAULT_DB;
+use prqlc::{ast, prql_to_tokens};
 use prqlc::{ir::pl::Lineage, ir::Span};
 use prqlc::{pl_to_prql, pl_to_rq_tree, prql_to_pl, prql_to_pl_tree, rq_to_sql, SourceTree};
 use prqlc::{Options, Target};
@@ -79,6 +79,14 @@ enum Command {
         format: Format,
     },
 
+    /// Lex into Tokens
+    Lex {
+        #[command(flatten)]
+        io_args: IoArgs,
+        #[arg(value_enum, long, default_value = "yaml")]
+        format: Format,
+    },
+
     /// Parse & generate PRQL code back
     #[command(name = "fmt")]
     Format {
@@ -288,6 +296,17 @@ impl Command {
                     Format::Yaml => serde_yaml::to_string(&ast)?.into_bytes(),
                 }
             }
+            Command::Lex { format, .. } => {
+                let s = sources.sources.values().exactly_one().or_else(|_| {
+                    // TODO: allow multiple sources
+                    bail!("Currently `lex` only works with a single source, but found multiple sources")
+                })?;
+                let tokens = prql_to_tokens(s)?;
+                match format {
+                    Format::Json => serde_json::to_string_pretty(&tokens)?.into_bytes(),
+                    Format::Yaml => serde_yaml::to_string(&tokens)?.into_bytes(),
+                }
+            }
             Command::Collect(_) => {
                 let mut root_module_def = prql_to_pl_tree(sources)?;
 
@@ -429,7 +448,7 @@ impl Command {
                 }
             }
 
-            _ => unreachable!(),
+            _ => unreachable!("Other commands shouldn't reach `execute`"),
         })
     }
 
@@ -438,11 +457,10 @@ impl Command {
         // `input`, rather than matching on them and grabbing `input` from
         // `self`? But possibly if everything moves to `io_args`, then this is
         // quite reasonable?
-        use Command::{
-            Collect, Debug, Experimental, Parse, Resolve, SQLAnchor, SQLCompile, SQLPreprocess,
-        };
+        use Command::*;
         let io_args = match self {
             Parse { io_args, .. }
+            | Lex { io_args, .. }
             | Collect(io_args)
             | Resolve { io_args, .. }
             | SQLCompile { io_args, .. }
@@ -481,10 +499,11 @@ impl Command {
 
     fn write_output(&mut self, data: &[u8]) -> std::io::Result<()> {
         use Command::{
-            Collect, Debug, Experimental, Parse, Resolve, SQLAnchor, SQLCompile, SQLPreprocess,
+            Collect, Debug, Experimental, Lex, Parse, Resolve, SQLAnchor, SQLCompile, SQLPreprocess,
         };
         let mut output = match self {
             Parse { io_args, .. }
+            | Lex { io_args, .. }
             | Collect(io_args)
             | Resolve { io_args, .. }
             | SQLCompile { io_args, .. }
@@ -815,4 +834,42 @@ sort full
               column: 2
         "###);
     }
+
+    #[test]
+    fn lex() {
+        let output = Command::execute(
+            &Command::Lex {
+                io_args: IoArgs::default(),
+                format: Format::Yaml,
+            },
+            &mut "from x | select y".into(),
+            "",
+        )
+        .unwrap();
+
+        // TODO: terser output; maybe serialize span as `0..4`? Remove the
+        // `!Ident` complication?
+        assert_snapshot!(String::from_utf8(output).unwrap().trim(), @r###"
+        - kind: !Ident from
+          span:
+            start: 0
+            end: 4
+        - kind: !Ident x
+          span:
+            start: 5
+            end: 6
+        - kind: !Control '|'
+          span:
+            start: 7
+            end: 8
+        - kind: !Ident select
+          span:
+            start: 9
+            end: 15
+        - kind: !Ident y
+          span:
+            start: 16
+            end: 17
+        "###);
+    }
 }

prqlc/prqlc/src/error_message.rs

@@ -87,6 +87,12 @@ impl From<Error> for ErrorMessage {
     }
 }
 
+impl From<Vec<ErrorMessage>> for ErrorMessages {
+    fn from(errors: Vec<ErrorMessage>) -> Self {
+        ErrorMessages { inner: errors }
+    }
+}
+
 #[derive(Debug, Clone, Serialize)]
 pub struct ErrorMessages {
     pub inner: Vec<ErrorMessage>,

prqlc/prqlc/src/lib.rs

@@ -113,6 +113,7 @@ pub static COMPILER_VERSION: Lazy<Version> =
     Lazy::new(|| Version::parse(env!("CARGO_PKG_VERSION")).expect("Invalid prqlc version number"));
 
 use once_cell::sync::Lazy;
+use prqlc_parser::TokenVec;
 use semver::Version;
 use serde::{Deserialize, Serialize};
 use std::{collections::HashMap, path::PathBuf, str::FromStr};
@@ -306,6 +307,16 @@ pub enum DisplayOptions {
 #[cfg(doctest)]
 pub struct ReadmeDoctests;
 
+/// Lex PRQL source into tokens.
+pub fn prql_to_tokens(prql: &str) -> Result<TokenVec, ErrorMessages> {
+    prqlc_parser::lex_source(prql).map_err(|e| {
+        e.into_iter()
+            .map(|e| e.into())
+            .collect::<Vec<ErrorMessage>>()
+            .into()
+    })
+}
+
 /// Parse PRQL into a PL AST
 // TODO: rename this to `prql_to_pl_simple`
 pub fn prql_to_pl(prql: &str) -> Result<ast::ModuleDef, ErrorMessages> {

prqlc/prqlc/tests/integration/cli.rs

@@ -17,6 +17,7 @@ fn help() {
 
     Commands:
       parse             Parse into PL AST
+      lex               Lex into Tokens
       fmt               Parse & generate PRQL code back
       collect           Parse the whole project and collect it into a single PRQL source file
       debug             Commands for meant for debugging, prone to change
@@ -471,3 +472,49 @@ fn compile_no_prql_files() {
 
     "###);
 }
+
+#[test]
+fn lex() {
+    assert_cmd_snapshot!(prqlc_command().args(["lex"]).pass_stdin("from tracks"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    - kind: !Ident from
+      span:
+        start: 0
+        end: 4
+    - kind: !Ident tracks
+      span:
+        start: 5
+        end: 11
+
+    ----- stderr -----
+    "###);
+
+    assert_cmd_snapshot!(prqlc_command().args(["lex", "--format=json"]).pass_stdin("from tracks"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    [
+      {
+        "kind": {
+          "Ident": "from"
+        },
+        "span": {
+          "start": 0,
+          "end": 4
+        }
+      },
+      {
+        "kind": {
+          "Ident": "tracks"
+        },
+        "span": {
+          "start": 5,
+          "end": 11
+        }
+      }
+    ]
+    ----- stderr -----
+    "###);
+}