Extract configuration snippet tests into own module (#3667)

* Extract configuration snippet tests into own module

* Move helper function outside of test function

src/test/configuration_snippet.rs

@@ -0,0 +1,286 @@
+use std::collections::{HashMap, HashSet};
+use std::fs;
+use std::io::{BufRead, BufReader, Write};
+use std::iter::Enumerate;
+use std::path::{Path, PathBuf};
+
+use super::{print_mismatches, write_message, DIFF_CONTEXT_SIZE};
+use crate::config::{Config, EmitMode, Verbosity};
+use crate::rustfmt_diff::{make_diff, Mismatch};
+use crate::{Input, Session};
+
+const CONFIGURATIONS_FILE_NAME: &str = "Configurations.md";
+
+// This enum is used to represent one of three text features in Configurations.md: a block of code
+// with its starting line number, the name of a rustfmt configuration option, or the value of a
+// rustfmt configuration option.
+enum ConfigurationSection {
+    CodeBlock((String, u32)), // (String: block of code, u32: line number of code block start)
+    ConfigName(String),
+    ConfigValue(String),
+}
+
+impl ConfigurationSection {
+    fn get_section<I: Iterator<Item = String>>(
+        file: &mut Enumerate<I>,
+    ) -> Option<ConfigurationSection> {
+        lazy_static! {
+            static ref CONFIG_NAME_REGEX: regex::Regex =
+                regex::Regex::new(r"^## `([^`]+)`").expect("failed creating configuration pattern");
+            static ref CONFIG_VALUE_REGEX: regex::Regex =
+                regex::Regex::new(r#"^#### `"?([^`"]+)"?`"#)
+                    .expect("failed creating configuration value pattern");
+        }
+
+        loop {
+            match file.next() {
+                Some((i, line)) => {
+                    if line.starts_with("```rust") {
+                        // Get the lines of the code block.
+                        let lines: Vec<String> = file
+                            .map(|(_i, l)| l)
+                            .take_while(|l| !l.starts_with("```"))
+                            .collect();
+                        let block = format!("{}\n", lines.join("\n"));
+
+                        // +1 to translate to one-based indexing
+                        // +1 to get to first line of code (line after "```")
+                        let start_line = (i + 2) as u32;
+
+                        return Some(ConfigurationSection::CodeBlock((block, start_line)));
+                    } else if let Some(c) = CONFIG_NAME_REGEX.captures(&line) {
+                        return Some(ConfigurationSection::ConfigName(String::from(&c[1])));
+                    } else if let Some(c) = CONFIG_VALUE_REGEX.captures(&line) {
+                        return Some(ConfigurationSection::ConfigValue(String::from(&c[1])));
+                    }
+                }
+                None => return None, // reached the end of the file
+            }
+        }
+    }
+}
+
+// This struct stores the information about code blocks in the configurations
+// file, formats the code blocks, and prints formatting errors.
+struct ConfigCodeBlock {
+    config_name: Option<String>,
+    config_value: Option<String>,
+    code_block: Option<String>,
+    code_block_start: Option<u32>,
+}
+
+impl ConfigCodeBlock {
+    fn new() -> ConfigCodeBlock {
+        ConfigCodeBlock {
+            config_name: None,
+            config_value: None,
+            code_block: None,
+            code_block_start: None,
+        }
+    }
+
+    fn set_config_name(&mut self, name: Option<String>) {
+        self.config_name = name;
+        self.config_value = None;
+    }
+
+    fn set_config_value(&mut self, value: Option<String>) {
+        self.config_value = value;
+    }
+
+    fn set_code_block(&mut self, code_block: String, code_block_start: u32) {
+        self.code_block = Some(code_block);
+        self.code_block_start = Some(code_block_start);
+    }
+
+    fn get_block_config(&self) -> Config {
+        let mut config = Config::default();
+        config.set().verbose(Verbosity::Quiet);
+        if self.config_name.is_some() && self.config_value.is_some() {
+            config.override_value(
+                self.config_name.as_ref().unwrap(),
+                self.config_value.as_ref().unwrap(),
+            );
+        }
+        config
+    }
+
+    fn code_block_valid(&self) -> bool {
+        // We never expect to not have a code block.
+        assert!(self.code_block.is_some() && self.code_block_start.is_some());
+
+        // See if code block begins with #![rustfmt::skip].
+        let fmt_skip = self
+            .code_block
+            .as_ref()
+            .unwrap()
+            .lines()
+            .nth(0)
+            .unwrap_or("")
+            == "#![rustfmt::skip]";
+
+        if self.config_name.is_none() && !fmt_skip {
+            write_message(&format!(
+                "No configuration name for {}:{}",
+                CONFIGURATIONS_FILE_NAME,
+                self.code_block_start.unwrap()
+            ));
+            return false;
+        }
+        if self.config_value.is_none() && !fmt_skip {
+            write_message(&format!(
+                "No configuration value for {}:{}",
+                CONFIGURATIONS_FILE_NAME,
+                self.code_block_start.unwrap()
+            ));
+            return false;
+        }
+        true
+    }
+
+    fn has_parsing_errors<T: Write>(&self, session: &Session<'_, T>) -> bool {
+        if session.has_parsing_errors() {
+            write_message(&format!(
+                "\u{261d}\u{1f3fd} Cannot format {}:{}",
+                CONFIGURATIONS_FILE_NAME,
+                self.code_block_start.unwrap()
+            ));
+            return true;
+        }
+
+        false
+    }
+
+    fn print_diff(&self, compare: Vec<Mismatch>) {
+        let mut mismatches = HashMap::new();
+        mismatches.insert(PathBuf::from(CONFIGURATIONS_FILE_NAME), compare);
+        print_mismatches(mismatches, |line_num| {
+            format!(
+                "\nMismatch at {}:{}:",
+                CONFIGURATIONS_FILE_NAME,
+                line_num + self.code_block_start.unwrap() - 1
+            )
+        });
+    }
+
+    fn formatted_has_diff(&self, text: &str) -> bool {
+        let compare = make_diff(self.code_block.as_ref().unwrap(), text, DIFF_CONTEXT_SIZE);
+        if !compare.is_empty() {
+            self.print_diff(compare);
+            return true;
+        }
+
+        false
+    }
+
+    // Return a bool indicating if formatting this code block is an idempotent
+    // operation. This function also triggers printing any formatting failure
+    // messages.
+    fn formatted_is_idempotent(&self) -> bool {
+        // Verify that we have all of the expected information.
+        if !self.code_block_valid() {
+            return false;
+        }
+
+        let input = Input::Text(self.code_block.as_ref().unwrap().to_owned());
+        let mut config = self.get_block_config();
+        config.set().emit_mode(EmitMode::Stdout);
+        let mut buf: Vec<u8> = vec![];
+
+        {
+            let mut session = Session::new(config, Some(&mut buf));
+            session.format(input).unwrap();
+            if self.has_parsing_errors(&session) {
+                return false;
+            }
+        }
+
+        !self.formatted_has_diff(&String::from_utf8(buf).unwrap())
+    }
+
+    // Extract a code block from the iterator. Behavior:
+    // - Rust code blocks are identifed by lines beginning with "```rust".
+    // - One explicit configuration setting is supported per code block.
+    // - Rust code blocks with no configuration setting are illegal and cause an
+    //   assertion failure, unless the snippet begins with #![rustfmt::skip].
+    // - Configuration names in Configurations.md must be in the form of
+    //   "## `NAME`".
+    // - Configuration values in Configurations.md must be in the form of
+    //   "#### `VALUE`".
+    fn extract<I: Iterator<Item = String>>(
+        file: &mut Enumerate<I>,
+        prev: Option<&ConfigCodeBlock>,
+        hash_set: &mut HashSet<String>,
+    ) -> Option<ConfigCodeBlock> {
+        let mut code_block = ConfigCodeBlock::new();
+        code_block.config_name = prev.and_then(|cb| cb.config_name.clone());
+
+        loop {
+            match ConfigurationSection::get_section(file) {
+                Some(ConfigurationSection::CodeBlock((block, start_line))) => {
+                    code_block.set_code_block(block, start_line);
+                    break;
+                }
+                Some(ConfigurationSection::ConfigName(name)) => {
+                    assert!(
+                        Config::is_valid_name(&name),
+                        "an unknown configuration option was found: {}",
+                        name
+                    );
+                    assert!(
+                        hash_set.remove(&name),
+                        "multiple configuration guides found for option {}",
+                        name
+                    );
+                    code_block.set_config_name(Some(name));
+                }
+                Some(ConfigurationSection::ConfigValue(value)) => {
+                    code_block.set_config_value(Some(value));
+                }
+                None => return None, // end of file was reached
+            }
+        }
+
+        Some(code_block)
+    }
+}
+
+#[test]
+fn configuration_snippet_tests() {
+    let blocks = get_code_blocks();
+    let failures = blocks
+        .iter()
+        .map(ConfigCodeBlock::formatted_is_idempotent)
+        .fold(0, |acc, r| acc + (!r as u32));
+
+    // Display results.
+    println!("Ran {} configurations tests.", blocks.len());
+    assert_eq!(failures, 0, "{} configurations tests failed", failures);
+}
+
+// Read Configurations.md and build a `Vec` of `ConfigCodeBlock` structs with one
+// entry for each Rust code block found.
+fn get_code_blocks() -> Vec<ConfigCodeBlock> {
+    let mut file_iter = BufReader::new(
+        fs::File::open(Path::new(CONFIGURATIONS_FILE_NAME))
+            .unwrap_or_else(|_| panic!("couldn't read file {}", CONFIGURATIONS_FILE_NAME)),
+    )
+    .lines()
+    .map(Result::unwrap)
+    .enumerate();
+    let mut code_blocks: Vec<ConfigCodeBlock> = Vec::new();
+    let mut hash_set = Config::hash_set();
+
+    while let Some(cb) = ConfigCodeBlock::extract(&mut file_iter, code_blocks.last(), &mut hash_set)
+    {
+        code_blocks.push(cb);
+    }
+
+    for name in hash_set {
+        if !Config::is_hidden_option(&name) {
+            panic!("{} does not have a configuration guide", name);
+        }
+    }
+
+    code_blocks
+}