Implement GitHub reference detection (#98)

This commit only adds logic for finding references in GitHub posts,
either by #-numeric reference, or explicit urls. Adding the reference
edges to the graph will occur in a followon commit.

Test plan: New unit tests are included

src/plugins/github/parseReferences.js

@@ -0,0 +1,65 @@
+// @flow
+
+function findAllMatches(re: RegExp, s: string): any[] {
+  // modified from: https://stackoverflow.com/a/6323598
+  let m;
+  const matches = [];
+  do {
+    m = re.exec(s);
+    if (m) {
+      matches.push(m);
+    }
+  } while (m);
+  return matches;
+}
+
+export function findNumericReferences(body: string): number[] {
+  return findAllMatches(/(?:\W|^)#(\d+)(?:\W|$)/g, body).map((x) => +x[1]);
+}
+
+export type GithubUrlMatch = {|
+  +repoName: string,
+  +repoOwner: string,
+  +parentType: "pull" | "issues",
+  +number: number,
+  +commentFragment: ?{|
+    +fragmentType:
+      | "issue" // a directly linked issue or pull request
+      | "issuecomment" // a directly linked regular comment on issue or pull request
+      | "pullrequestreview" // a pull request review
+      | "discussion_r", // a review comment as part of a pull request review
+    +fragmentNumber: number,
+  |},
+|};
+
+export function findGithubUrlReferences(body: string): GithubUrlMatch[] {
+  const githubNamePart = /([a-zA-Z0-9_-]+)/.source;
+  const urlRegex = new RegExp(
+    "" +
+      /(?:\W|^)http(?:s)?:\/\/github.com\//.source +
+      githubNamePart +
+      /\//.source +
+      githubNamePart +
+      /\/(issues|pull)\//.source +
+      /(\d+)/.source +
+      /(#(issue|issuecomment|pullrequestreview|discussion_r)-?(\d+))?/.source +
+      /(?:\W|$)/.source,
+    "gm"
+  );
+  return findAllMatches(urlRegex, body).map((match) => {
+    let commentFragment: $ElementType<GithubUrlMatch, "commentFragment">;
+    if (match[5] != null) {
+      // we found a comment fragment
+      commentFragment = {fragmentType: match[6], fragmentNumber: +match[7]};
+    } else {
+      commentFragment = null;
+    }
+    return {
+      repoOwner: match[1],
+      repoName: match[2],
+      parentType: match[3],
+      number: +match[4],
+      commentFragment,
+    };
+  });
+}

src/plugins/github/parseReferences.test.js

@@ -0,0 +1,170 @@
+// @flow
+
+import {
+  findNumericReferences,
+  findGithubUrlReferences,
+} from "./parseReferences.js";
+import type {GithubUrlMatch} from "./parseReferences.js";
+
+describe("reference finding", () => {
+  it("finds no numeric references when not present", () => {
+    expect(findNumericReferences("foo bar bod boink")).toHaveLength(0);
+    expect(findNumericReferences("")).toHaveLength(0);
+  });
+
+  it("finds trivial numeric references", () => {
+    expect(findNumericReferences("#1, #2, and #3")).toEqual([1, 2, 3]);
+  });
+
+  it("finds numeric references in a multiline string", () => {
+    const example = `
+    This is a multiline string.
+    It refers to #1. Oh, and to #2 too.
+    (#42 might be included too - who knows?)`;
+    expect(findNumericReferences(example)).toEqual([1, 2, 42]);
+  });
+
+  it("does not find bad references", () => {
+    expect(findNumericReferences("foo#123 #124bar")).toHaveLength(0);
+  });
+
+  it("does not yet find concise cross-repo links", () => {
+    // The link below is valid, when we add cross-repo support we
+    // should fix this test case
+    expect(findNumericReferences("sourcecred/sourcecred#12")).toHaveLength(0);
+  });
+
+  it("finds no url references when not present", () => {
+    expect(findGithubUrlReferences("foo bar bod boink")).toHaveLength(0);
+    expect(findGithubUrlReferences("")).toHaveLength(0);
+  });
+
+  it("finds a trivial url reference", () => {
+    expect(
+      findGithubUrlReferences(
+        "https://github.com/sourcecred/sourcecred/issues/86"
+      )
+    ).toHaveLength(1);
+  });
+
+  it("parses url references appropriately", () => {
+    const example = `
+    A directly linked issue:
+https://github.com/sourcecred/example-repo/issues/1
+
+    A directly linked issue with fragment:
+https://github.com/sourcecred/example-repo/issues/1#issue-300934818
+
+    A directly linked pull request:
+https://github.com/sourcecred/example-repo/pull/3
+
+    A directly linked pull request with fragment:
+https://github.com/sourcecred/example-repo/pull/3#issue-171887741
+
+    A directly linked issue comment:
+https://github.com/sourcecred/example-repo/issues/6#issuecomment-373768442
+
+    A directly linked pull request review:
+https://github.com/sourcecred/example-repo/pull/5#pullrequestreview-100313899
+
+    A directly linked pull request review comment:
+https://github.com/sourcecred/example-repo/pull/5#discussion_r171460198
+
+    A directly linked pull request comment:
+https://github.com/sourcecred/example-repo/pull/3#issuecomment-369162222
+    `;
+
+    const expected = [
+      {
+        repoName: "example-repo",
+        repoOwner: "sourcecred",
+        parentType: "issues",
+        number: 1,
+        commentFragment: null,
+      },
+      {
+        repoName: "example-repo",
+        repoOwner: "sourcecred",
+        parentType: "issues",
+        number: 1,
+        commentFragment: {fragmentType: "issue", fragmentNumber: 300934818},
+      },
+      {
+        repoName: "example-repo",
+        repoOwner: "sourcecred",
+        parentType: "pull",
+        number: 3,
+        commentFragment: null,
+      },
+      {
+        repoName: "example-repo",
+        repoOwner: "sourcecred",
+        parentType: "pull",
+        number: 3,
+        commentFragment: {fragmentType: "issue", fragmentNumber: 171887741},
+      },
+      {
+        repoName: "example-repo",
+        repoOwner: "sourcecred",
+        parentType: "issues",
+        number: 6,
+        commentFragment: {
+          fragmentType: "issuecomment",
+          fragmentNumber: 373768442,
+        },
+      },
+      {
+        repoName: "example-repo",
+        repoOwner: "sourcecred",
+        parentType: "pull",
+        number: 5,
+        commentFragment: {
+          fragmentType: "pullrequestreview",
+          fragmentNumber: 100313899,
+        },
+      },
+      {
+        repoName: "example-repo",
+        repoOwner: "sourcecred",
+        parentType: "pull",
+        number: 5,
+        commentFragment: {
+          fragmentType: "discussion_r",
+          fragmentNumber: 171460198,
+        },
+      },
+      {
+        repoName: "example-repo",
+        repoOwner: "sourcecred",
+        parentType: "pull",
+        number: 3,
+        commentFragment: {
+          fragmentType: "issuecomment",
+          fragmentNumber: 369162222,
+        },
+      },
+    ];
+
+    expect(findGithubUrlReferences(example)).toEqual(expected);
+  });
+
+  it("doesn't find urls mangled with word characters", () => {
+    expect(
+      findGithubUrlReferences(
+        "foohttps://github.com/sourcecred/sourcecred/pull/94"
+      )
+    ).toHaveLength(0);
+
+    expect(
+      findGithubUrlReferences(
+        "https://github.com/sourcecred/sourcecred/pull/94foo"
+      )
+    ).toHaveLength(0);
+
+    expect(
+      findGithubUrlReferences(
+        "(https://github.com/sourcecred/sourcecred/pull/94)"
+      )
+    ).toHaveLength(1);
+  });
+});