From a40d02c9eb1c7226bc7db87b014dc827e77f2a08 Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Thu, 24 Oct 2019 19:29:38 +0300
Subject: refactor comment extraction from tasks

---
 xtask/src/codegen.rs                  | 25 ++++++++++++++-
 xtask/src/codegen/gen_parser_tests.rs | 58 ++++++++++++-----------------------
 2 files changed, 44 insertions(+), 39 deletions(-)

diff --git a/xtask/src/codegen.rs b/xtask/src/codegen.rs
index 948b86719..bf3a90119 100644
--- a/xtask/src/codegen.rs
+++ b/xtask/src/codegen.rs
@@ -8,7 +8,7 @@
 mod gen_syntax;
 mod gen_parser_tests;
 
-use std::{fs, path::Path};
+use std::{fs, mem, path::Path};
 
 use crate::Result;
 
@@ -44,3 +44,26 @@ pub fn update(path: &Path, contents: &str, mode: Mode) -> Result<()> {
     fs::write(path, contents)?;
     Ok(())
 }
+
+fn extract_comment_blocks(text: &str) -> Vec<Vec<String>> {
+    let mut res = Vec::new();
+
+    let prefix = "// ";
+    let lines = text.lines().map(str::trim_start);
+
+    let mut block = vec![];
+    for line in lines {
+        let is_comment = line.starts_with(prefix);
+        if is_comment {
+            block.push(line[prefix.len()..].to_string());
+        } else {
+            if !block.is_empty() {
+                res.push(mem::replace(&mut block, Vec::new()))
+            }
+        }
+    }
+    if !block.is_empty() {
+        res.push(mem::replace(&mut block, Vec::new()))
+    }
+    res
+}
diff --git a/xtask/src/codegen/gen_parser_tests.rs b/xtask/src/codegen/gen_parser_tests.rs
index e6eeb29a1..db1e59dac 100644
--- a/xtask/src/codegen/gen_parser_tests.rs
+++ b/xtask/src/codegen/gen_parser_tests.rs
@@ -3,12 +3,12 @@
 
 use std::{
     collections::HashMap,
-    fs,
+    fs, iter,
     path::{Path, PathBuf},
 };
 
 use crate::{
-    codegen::{self, update, Mode},
+    codegen::{self, extract_comment_blocks, update, Mode},
     project_root, Result,
 };
 
@@ -57,46 +57,28 @@ struct Tests {
 }
 
 fn collect_tests(s: &str) -> Vec<Test> {
-    let mut res = vec![];
-    let prefix = "// ";
-    let lines = s.lines().map(str::trim_start);
-
-    let mut block = vec![];
-    for line in lines {
-        let is_comment = line.starts_with(prefix);
-        if is_comment {
-            block.push(&line[prefix.len()..]);
+    let mut res = Vec::new();
+    for comment_block in extract_comment_blocks(s) {
+        let first_line = &comment_block[0];
+        let (name, ok) = if first_line.starts_with("test ") {
+            let name = first_line["test ".len()..].to_string();
+            (name, true)
+        } else if first_line.starts_with("test_err ") {
+            let name = first_line["test_err ".len()..].to_string();
+            (name, false)
         } else {
-            process_block(&mut res, &block);
-            block.clear();
-        }
-    }
-    process_block(&mut res, &block);
-    return res;
-
-    fn process_block(acc: &mut Vec<Test>, block: &[&str]) {
-        if block.is_empty() {
-            return;
-        }
-        let mut ok = true;
-        let mut block = block.iter();
-        let name = loop {
-            match block.next() {
-                Some(line) if line.starts_with("test ") => {
-                    break line["test ".len()..].to_string();
-                }
-                Some(line) if line.starts_with("test_err ") => {
-                    ok = false;
-                    break line["test_err ".len()..].to_string();
-                }
-                Some(_) => (),
-                None => return,
-            }
+            continue;
         };
-        let text: String = block.copied().chain(std::iter::once("")).collect::<Vec<_>>().join("\n");
+        let text: String = comment_block[1..]
+            .iter()
+            .cloned()
+            .chain(iter::once(String::new()))
+            .collect::<Vec<_>>()
+            .join("\n");
         assert!(!text.trim().is_empty() && text.ends_with('\n'));
-        acc.push(Test { name, text, ok })
+        res.push(Test { name, text, ok })
     }
+    res
 }
 
 fn tests_from_dir(dir: &Path) -> Result<Tests> {
-- 
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